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  • Elsevier  (923,527)
  • Springer  (767,898)
  • National Academy of Sciences  (51,283)
  • American Geophysical Union  (50,170)
  • Institute of Physics (IOP)
  • 2010-2014  (1,123,879)
  • 1990-1994  (674,854)
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  • 1
    Electronic Resource
    Electronic Resource
    A measurement of τ polarization in Z^0 decays (1992-8977)
    Amsterdam : Elsevier
    Physics Letters B 294 (1992), S. 466-478 
    Details
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0370-2693(92)91549-O
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Measurement of the average lifetime of b hadrons (1993-4325)
    Amsterdam : Elsevier
    Physics Letters B 317 (1993), S. 474-484 
    Details
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0370-2693(93)91027-K
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  • 3
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    A major change in the sedimentation regime in the Crotone Basin (Southern Italy) around 3.7-3.6 Ma (2014)
    Elsevier
    Details
    Publication Date: 2021-05-17
    Description: The Lower Pliocene succession of the Crotone Basin (Calabrian Arc, Southern Italy) is mainly comprised of blue-grey marly clay with good magnetic properties. Here the bio-magnetostratigraphic data indicate a mean sedimentation rate of about 12–15 cm/kyr. Around 3.7–3.6 Ma a major change in the sedimentation regime occurred: the blue-grey hemipelagic marls grade rapidly into silty marls with a significant increase in the terrigenous fraction and with abundant siliceous remains throughout the whole interval. Magnetic properties of these sediments are very poor, but an integrated calcareous plankton biostratigraphy (foraminifera and nannofossils) infers a high average sedimentation rate (about 50–60 cm/kyr). The abrupt onset of this sedimentation regime in the Crotone Basin is contemporaneous with a major unconformity already recognized in the northern sector of the basin, part of amajor reorganization phase in the whole Apenninic–Maghrebid Chain known as “Globorotalia puncticulata event”. Reports of coeval siliceous sediments in other marginal basins of the Apennines (Southern Calabria, Southern and Northern Apennines) suggest that this “siliceous event” might have been regionally extensive, having important palaeoceanographical implications.We infer that the “siliceous event” is characterized by a combined tectonic- and climate-induced change in palaeoceanographic conditions. The tectonic triggering factors may have been linked to two synchronous events in the Tyrrhenian–Apennine system: 1) the shortening event also known as “G. puncticulata event”, and 2) the coeval opening of the Vavilov Basin in the Tyrrhenian Sea which yielded profound influences in terms of physiography and characteristics of the Crotone Basin. The consequent uplift of the Southern Apennines would have increased sediment supply and availability of silica, resulting in eutrophication and enhanced silica preservation. Strong winter mixing and possibly upwelling conditions could have increased primary productivity during heavy isotope stages Gi4, Gi2 and MG8, at the onset of the “siliceous event”. This important event, lasting from ca. 3.6 Ma to ca. 3.2 Ma, would have recorded a peculiar transitional period before further climatic deterioration and more drastic palaeoceanographic changes occurred around 3.1 Ma, leading to cyclic sapropel deposition in the whole of the Mediterranean sea.
    Description: Published
    Description: 398-410
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Biostratigraphy ; Magnetostratigraphy ; Pliocene ; Calabrian Arc ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Mapping Moho depth variations in central Italy from PsMoho-P delay times: Evidence of an E-W transition in the Adriatic Moho at 42°N latitude (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-12-18
    Description: Along the Italian peninsula adjoin two crustal domains, peri-Tyrrhenian and Adriatic, whose boundary is not univocal in central Italy. In this area, we attempt to map the extent of the Moho in the two terrains from variations of the travel time difference between the direct P wave and the P-to-S wave converted at the crust-mantle boundary, called PsMoho. We use teleseismic receiver functions computed at 38 broad-band stations in this and previous studies, and assigned each of the recording sites to the Adriatic or peri-Tyrrhenian terrains based on station location, geologic and geophysical data and interpretation, and consistency of delays with the regional Moho trend. The results of the present study show that the PsMoho arrival time varies from 2.3 to 4.1 s in the peri-Tyrrhenian domain and from 3.7 to 5.5 s in the Adriatic domain. As expected, the lowest time difference is observed along the Tyrrhenian coastline and the largest values are observed in the axial zone of the Apennine chain. A key new result of this study is a sharp E-W boundary in the Adriatic domain that separates a deeper Moho north of about 42 N latitude from a shallower Moho to the south. This feature is constrained for a length of about 40 km by the observations available in this study. The E-W boundary requires a revision of prior mapping of the Moho in central Italy and supports previous hypotheses of lithosphere segmentation.
    Description: Published
    Description: 3929–3938
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: teleseismic receiver functions ; Moho discontinuity ; central Italy ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Low-temperature magnetic properties of pelagic carbonates: Oxidation of biogenic magnetite and identification of magnetosome chains (2014)
    American Geophysical Union
    Details
    Publication Date: 2021-02-17
    Description: Pelagic marine carbonates provide important records of past environmental change. We carried out detailed low-temperature magnetic measurements on biogenic magnetite-bearing sediments from the Southern Ocean (Ocean Drilling Program (ODP) Holes 738B, 738C, 689D, and 690C) and on samples containing whole magnetotactic bacteria cells. We document a range of low-temperature magnetic properties, including reversible humped low-temperature cycling (LTC) curves. Different degrees of magnetite oxidation are considered to be responsible for the observed variable shapes of LTC curves. A dipole spring mechanism in magnetosome chains is introduced to explain reversible LTC curves. This dipole spring mechanism is proposed to result from the uniaxial anisotropy that originates from the chain arrangement of biogenic magnetite, similar to published results for uniaxial stable single domain (SD) particles. The dipole spring mechanism reversibly restores the remanence during warming in LTC measurements. This supports a previous idea that remanence of magnetosome chains is completely reversible during LTC experiments. We suggest that this magnetic fingerprint is a diagnostic indicator for intact magnetosome chains, although the presence of isolated uniaxial stable SD particles and magnetically interacting particles can complicate this test. Magnetic measurements through the Eocene section of ODP Hole 738B reveal an interval with distinct magnetic properties that we interpret to originate from less oxidized biogenic magnetite and enrichment of a biogenic “hard” component. Co-occurrence of these two magnetic fingerprints during the late Eocene in the Southern Ocean indicates less oxic conditions, probably due to increased oceanic primary productivity and organic carbon burial.
    Description: Published
    Description: 6049–6065
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: pelagic carbonates ; biogenic magnetite ; rock magnetism ; environmental magnetism ; ODP ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Sudden deep gas eruption nearby Rome's airport of Fiumicino (2014)
    American Geophysical Union
    Details
    Publication Date: 2021-03-24
    Description: On 24 August 2013 a sudden gas eruption from the ground occurred in the Tiber river delta, nearby Rome's international airport of Fiumicino. We assessed that this gas, analogous to other minor vents in the area, is dominantly composed of deep, partially mantle-derived CO2, as in the geothermal gas of the surrounding Roman Comagmatic Province. Increased amounts of thermogenic CH4 are likely sourced from Meso-Cenozoic petroleum systems, overlying the deep magmatic fluids. We hypothesize that the intersection of NE-SW and N-S fault systems, which at regional scale controls the location of the Roman volcanic edifices, favors gas uprising through the impermeable Pliocene and deltaic Holocene covers. Pressurized gas may temporarily be stored below these covers or within shallower sandy, permeable layers. The eruption, regardless the triggering cause—natural or man-made, reveals the potential hazard of gas-charged sediments in the delta, even at distances far from the volcanic edifices.
    Description: Published
    Description: 5632–5636
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: geothermal gas ; deep CO2 ; Tiber river delta ; thermogenic CH4 ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Magnetic fabric of Plio-Pleistocene sediments from the Crotone fore-arc basin: Insights on the recent tectonic evolution of the Calabrian Arc (Italy) (2014)
    Elsevier
    Details
    Publication Date: 2020-12-07
    Description: Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples col-lected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, afore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formedsince mid-late Miocene under a predominant extensional tectonic regime, but it was influenced there-after by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yieldedpost-1.2 Ma ~30◦counterclockwise block rotations. The basin is filled by continental to marine sedimentsyielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marinefacies – represented by blue-grey marly clays gave the best results, as they both preserved a clear mag-netic fabric, and provided accurate chronology based on previously published magnetostratigraphy andcalcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility rangeand rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrange-ment. The fabric is predominantly oblate to triaxial, the anisotropy degree low (〈1.06), and the magneticfoliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where thee12 angle is 〈35◦). By also considering local structural analysis data, we find that magnetic fabric wasgenerally acquired during the first tectonic phases occurring after sediment deposition, thus validatingits use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE andare orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineationsshow that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes.Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault boundingthe basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basinshows a markedly different tectonics with respect to other internal and western basins of Calabria, asit yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal short-ening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin iscompatible with a continuous upper crustal structural reorganization occurring during the SE-migrationof the Calabria terrane above the Ionian subduction system.
    Description: Published
    Description: 67-79
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Calabrian Arc, Anisotropy of magnetic susceptibility, Structural analysis, Fore-arc region ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Cyanobacteria in Scandinavian coastal waters — A potential source for biofuels and fatty acids? (2014)
    Elsevier
    In:  EPIC3Algal Research, Elsevier, 5, pp. 42-51, ISSN: 2211-9264
    Details
    Publication Date: 2014-06-24
    Description: Since land-based biofuel production competes with conventional food production, a water-based biomass and biofuel production from cyanobacteria offers large potential. This study investigates the application potential of cyanobacteria for fuel production and by-products by mimicking nutrient depleted environmental conditions. Three Baltic cyanobacteria strains (Aphanizomenon flos-aquae, Dolichospermum lemmermannii and Nodularia spumigena) were inoculated in full nutrient levels, as well as phosphorus and nitrogen depleted medium, before being monitored for 14 days. For screening reasons, multiple parameters such as fatty acids, photosynthetic pigments including phycobilins, biovolume, photosynthetic activity, inorganic nutrients, particulate organic carbon, nitrogen and phosphorous were investigated every seven days. We observed a strong negative relationship between lipid content, growth and nutrient availability, resulting in high lipid and pigment production in combination with a limited growth rate in nutrient depleted treatments. Our results suggest that cultivation and harvest of bloom-forming cyanobacteria for fuel and by-product production are feasible in Scandinavia, but strongly depends on the desired compounds and biomass. Each cyanobacteria species originally has a species-specific chemical fingerprint that may be modified by rearing conditions and harvesting period to meet the needs of the consumer. This leads to important conclusions regarding future culturing conditions and biomass production of the desired compounds.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Biological validation of physical coastal waters classification along the NE Atlantic region based on rocky macroalgae distribution (2014)
    Elsevier
    In:  EPIC3Estuarine, Coastal and Shelf Science, Elsevier, 147, pp. 103-112, ISSN: 0272-7714
    Details
    Publication Date: 2014-06-30
    Description: A methodology to classify rocky shores along the North East Atlantic (NEA) region was developed. Previously, biotypes and the variability of environmental conditions within these were recognized based on abiotic data. A biological validation was required in order to support the ecological meaning of the physical typologies obtained. A database of intertidal macroalgae species occurring in the coastal area between Norway and the South Iberian Peninsula was generated. Semi-quantitative abundance data of the most representative macroalgal taxa were collected in three levels: common, rare or absent. Ordination and classification multivariate analyses revealed a clear latitudinal gradient in the distribution of macroalgae species resulting in two distinct groups: one northern and one southern group, separated at the coast of Brittany (France). In general, the results based on biological data coincided with the results based on physical characteristics. The ecological meaning of the coastal waters classification at a broad scale shown in this work demonstrates that it can be valuable as a practical tool for conservation and management purposes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
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    Neodymium and hafnium boundary contributions to seawater along the West Antarctic continental margin (2014)
    Elsevier
    In:  EPIC3Earth and Planetary Science Letters, Elsevier, 394, pp. 99-110, ISSN: 0012-821X
    Details
    Publication Date: 2018-08-10
    Description: Neodymium and hafnium isotopes and elemental concentrations (Sm, Nd, Hf, Zr) have been measured in three water column profiles south of the Antarctic Circumpolar Current in, and to the east of the Ross Sea, in conjunction with five bottom water samples from the Amundsen Sea Embayment. Neodymium and hafnium both appear to be released from sediments in the Embayment. In the case of Nd, this is reflected in radiogenic isotope compositions (εNd up to −5.4) and highly elevated concentrations (up to 41 pmol/kg). Hafnium isotopes, on the other hand, are only very slightly altered relative to the open ocean sites, and boundary release is most prominently indicated by elevated concentrations (〉1 pmol/kg versus ∼0.7 pmol/kg). There is also a local input of both Hf and Nd at the Marie Byrd Seamounts, which leads to Nd isotope compositions as radiogenic as −3.1, and hafnium shifted to less radiogenic compositions in local bottom water. A compilation of the new data with literature data reveals a consistent view of the influence of Antarctica on the Nd isotope composition in Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW). Sector specific Nd addition shifts AABW formed in the Atlantic sector to less radiogenic isotope compositions (average εNd = −9) relative to LCDW (average εNd = −8.4), whereas AABW in the Pacific sector is shifted to more radiogenic values (average εNd = −7). The evolution towards more radiogenic εNd with depth in LCDW in the Pacific sector is likely to reflect admixture of AABW but, in addition, is also controlled by boundary exchange with the slope as observed at the Marie Byrd Seamounts. Hafnium isotopes are relatively homogeneous in the data set, ranging between εHf = +2 and +3.8 for most samples, excluding less radiogenic compositions in deep waters close to the Marie Byrd Seamounts. The Hf isotope composition in the Pacific sector is, however, slightly less radiogenic than in the Atlantic, corresponding to an average of +3 relative to an average of +3.8. This probably reflects unradiogenic Hf inputs from Antarctica to the Pacific sector, which are vertically homogenized by reversible scavenging. The Hf isotope heterogeneity in LCDW between both sectors is likely to indicate a shorter seawater residence time for Hf than for Nd, which is consistent with the dissolved – particulate phase partitioning of both elements
    Repository Name: EPIC Alfred Wegener Institut
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  • 11
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    Insolation and glacial–interglacial control on southwestern African hydroclimate over the past 140000 years (2014)
    Elsevier
    In:  EPIC3Earth and Planetary Science Letters, Elsevier, 398, pp. 1-10, ISSN: 0012-821X
    Details
    Publication Date: 2014-06-27
    Description: The past climate evolution of southwestern Africa is poorly understood and interpretations of past hydrological changes are sometimes The past climate evolution of southwestern Africa is poorly understood and interpretations of past hydrological changes are sometimes contradictory. Here we present a record of leaf-wax δD and δ13C taken from a marine sediment core at 23°S off the coast of Namibia to reconstruct the hydrology and C3 versus C4 vegetation of southwestern Africa over the last 140 000 years (140 ka). We find lower leaf-wax δD and higher δ13C (more C4 grasses), which we interpret to indicate wetter Southern Hemisphere (SH) summer conditions and increased seasonality, during SH insolation maxima relative to minima and during the last glacial period relative to the Holocene and the last interglacial period. Nonetheless, the dominance of C4 grasses throughout the record indicates that the wet season remained brief and that this region has remained semi-arid. Our data suggest that past precipitation increases were derived from the tropics rather than from the winter westerlies. Comparison with a record from the Congo Basin indicates that hydroclimate in southwestern Africa has evolved in antiphase with that of central Africa over the last 140 ka.
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
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    The Gordian knot of mangrove conservation: Disentangling the role of scale, services and benefits (2014)
    Elsevier
    In:  EPIC3Global Environmental Change, Elsevier, 28, pp. 120-128, ISSN: 0959-3780
    Details
    Publication Date: 2016-10-07
    Description: Mangrove forests are among the most threatened tropical ecosystems. Their role as providers of important ecosystem services such as coastal protection, carbon storage and nursery habitats for economically important species is increasingly acknowledged. But mangrove destruction continues, and we might have to face the prospect of a world deprived of the services offered by mangrove ecosystems. Mangrove transformation and destruction is often caused by mismatches in mangrove system management. These root in interests that focus on selected ecosystem services only, but also result from a problem of fit between the spatial scales at which ecosystem services are provided, and those at which their benefits are realized. We argue that a combination of the ecosystem services concept with a careful approach to the issue of scales will help to overcome these problems and improve the management of mangrove systems. Drawing on two case studies from Indonesia and Brazil, we illustrate the relevance of our findings for different ecosystem services.
    Repository Name: EPIC Alfred Wegener Institut
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  • 13
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    Impact of recirculation on the East Greenland Current in Fram Strait: Results from moored current meter measurements between 1997 and 2009 (2014)
    Elsevier
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 92, pp. 26-40, ISSN: 0967-0637
    Details
    Publication Date: 2014-09-09
    Description: Transports of total volume and water masses obtained from a mooring array in the East Greenland Current (EGC) in Fram Strait are presented for the period 1997–2009. The array in the EGC was moved along isobaths from 79°N to 78°50′N78°50′N in 2002 to line up with moorings in the eastern Fram Strait. Analysis of the time series at the two latitudes shows that associated with the southward move, the annual mean volume transport of the EGC increased from 5.8±1.8 Sv to 8.7±2.5 Sv, mostly related with an increase in barotropic flow. This suggests a recirculation of close to 3 Sv at 78°50′N78°50′N as a consequence of the large-scale wind-driven cyclonic gyre in the Nordic Seas. In addition, the volume transport at 78°50′N78°50′N showed a clear seasonal cycle which was absent at 79°N. Estimates of the wind-driven Sverdrup transport at two different latitudes show that the difference in total volume transport and seasonality can largely be explained by the wind-stress curl. However, weak transport in 2003 was only partially related with weak Sverdrup transport and coincided also with anomalously weak northerly winds. The stronger recirculation at 78°50′N78°50′N has also consequences for the observed Atlantic Water: there is significantly more Atlantic derived water present at the southerly latitude. In addition, the warm anomaly in Fram Strait between 2005 and 2007 doubled the amount of Recirculated Atlantic Water temporarily. Finally, we estimate that close to 2.7 Sv, or 50%, of Atlantic derived water recirculates in Fram Strait.
    Repository Name: EPIC Alfred Wegener Institut
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  • 14
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    Marine viruses: the beneficial side of a threat (2014)
    Springer
    In:  EPIC3Applied Biochemistry and Biotechnology, Springer, ISSN: 0273-2289
    Details
    Publication Date: 2014-09-30
    Description: Marine viruses are ubiquitous, extremely diverse, and outnumber any form of life in the sea. Despite their ecological importance, viruses in marine environments have been largely ignored by the academic community, and only those that have caused substantial economic losses have received more attention. Fortunately, our current understanding on marine viruses has advanced considerably during the last decades. These advances have opened new and exciting research opportunities as several unique structural and genetic characteristics of marine viruses have shown to possess an immense potential for various biotechnological applications. Here, a condensed overview of the possibilities of using the enormous potential offered by marine viruses to develop innovative products in industries as pharmaceuticals, environmental remediation, cosmetics, material sciences, and several others, is presented. The importance of marine viruses to biotechnology should not be underestimated.
    Repository Name: EPIC Alfred Wegener Institut
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  • 15
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    Ocean Acidification and Oceanic Carbon Cycling (2014)
    Springer
    In:  EPIC3Global Environmental Change, (Handbook of Global Environmental Pollution ;1), Dordrecht ; London, Springer, 973 p., pp. 103-110, ISBN: 978-94-007-5783-7
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    Publication Date: 2014-10-08
    Repository Name: EPIC Alfred Wegener Institut
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  • 16
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    Biome distribution over the last 22,000 yr in China (2014)
    Elsevier
    In:  EPIC3Palaeogeography, Palaeoclimatology, Palaeoecology, Elsevier, 409, pp. 33-47, ISSN: 0031-0182
    Details
    Publication Date: 2019-08-23
    Description: Patterns of past vegetation changes over time and space can help facilitate better understanding of the interactions among climate, ecosystem, and human impact. Biome changes in China over the last 22,000 yr (calibrated radiocarbon date, a BP) were numerically reconstructed by using a standard approach of pollen-plant functional type-biome assignment (biomization). The biomization procedure involves pollen data from 2434 surface sites and 228 fossil sites with a high quality of pollen count and 14C dating, 51 natural and three anthropogenic plant functional types (PFTs), as well as 19 natural and one anthropogenic biome. Surface pollen-based reconstruction of modern natural biome patterns is in good agreement (74.4%) with actual vegetation distribution in China. However, modern large-scale anthropogenic biome reconstruction has not been successful based on the current setup of three anthropogenic PFTs (plantation, secondary, and disturbed PFT) because of the limitation of non-species level pollen identification and the difficulty in the clear assignment of disturbed PFTs. The non-anthropogenic biome distributions of 44 time slices at 500-year intervals show large-scale discrepant and changed vegetation patterns from the last glacial maximum (LGM) to the Holocene throughout China. From 22 ka BP to 19 ka BP, temperate grassland, xerophytic shrubland, and desert dominated northern China,whereas cold or cool forests flourished in central China.Warm–temperate evergreen forests were restricted to far southern China, and tropical forestswere absent. During 18.5 ka BP to 12 ka BP, cold, cool, and dry biomes extended to someparts of northern,western, and eastern China.Warm–temperate evergreen andmixed forests gradually expanded to occupy thewhole of southern China. A slight northward shift of forest biomes occurred from15 ka BP to 12 ka BP. During 11.5 ka BP to 9 ka BP, temperate grassland and shrubland gradually stretched to northern and western China. Cold and cool forestswidely expanded into northern and central China, aswell as in the northern margin of South China along with temperate deciduous forest. Since the early mid-Holocene (approximately 8.5 ka BP to 5.5 ka BP), all forest biomes shifted northward at the expense of herbaceous and shrubby biomes. Simultaneously, cold and cool forest biomes occupied the marginal areas of the Tibetan Plateau and the high mountains in western China. During the middle to late Holocene, from 5 ka to the present, temperate grassland and xerophytic shrubland expanded to the south and east, whereas temperate deciduous forests slightly shifted southward. After 3 ka BP, forest biomes were absent in western China and on the Tibetan plateau surface. Dramatic biome shifts from theLGM to the Holocene were observed in the forest-grassland ecotone and transitional zones between temperate and subtropical climates, between subtropical and tropical regions, and in the mountainous margins of the eastern Tibetan Plateau. Evidence showed more human disturbances during the late Holocene. More pollen records and historical documents are therefore further needed to understand fully the human disturbance-induced large-scale forest changes. In addition, more classifications of anthropogenic biome or land cover, more distinct assignment of pollen taxa to anthropogenic PFTs, and more effective numerical and/or mechanistic techniques in building large-scale human disturbances are required.
    Repository Name: EPIC Alfred Wegener Institut
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  • 17
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    Dissolved methane concentration and flux in the coastal zone of the Southern California Bight-Mexican sector: Possible influence of wastewater (2014)
    Elsevier
    In:  EPIC3Estuarine, Coastal and Shelf Science, Elsevier, 144, pp. 65-74, ISSN: 0272-7714
    Details
    Publication Date: 2014-07-14
    Description: We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern California Bight-Mexican sector (SCBMex) during two cruises: S1 in the USA–Mexico Border Area (BA) during a short rainstorm and S2 in the entire SCBMex during a drier period a few days later. High spatial variability in surface mixed layer (ML) [CH4] was observed, ranging from 2.2 nmol L−1 to 17.8 nmol L−1. ML-[CH4] was supersaturated at all BA stations during both cruises. The highest [CH4] was 72.4 nmol L−1 (2819 % supersaturated) measured at 10 m depth during S2, about 3 km southwest of the discharge point of the South Bay Ocean Outfall (SBOO). Our results show an apparent connection between wastewater treatment discharges and [CH4]. Application of a sewer CH4 production model suggests that the SBOO may be a large source of CH4 to the BA and points to the need to consider point sources in developing coastal marine CH4 budgets for highly populated areas. Based on our data, the SCBMex appears to be a relatively strong source of CH4 to the atmosphere compared to other Pacific Basin areas. The average BA sea-to-air CH4 flux (F) during S1 was (15.5 ± 8.6) × 10−2 nmol m−2 s−1, about 1.5 times higher than F during S2, which had a flux of (9.5 ± 6.9) × 10−2 nmol m−2 s−1 mainly due to the higher wind speed during S1.
    Repository Name: EPIC Alfred Wegener Institut
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    Development of the Western Boundary Undercurrent at Eirik Drift related to changing climate since the early Miocene (2014)
    Elsevier
    In:  EPIC3Deep Sea Research I: Oceanographic Research Papers, Elsevier, 93, pp. 21-34, ISSN: 0967-0637
    Details
    Publication Date: 2019-07-16
    Description: Eirik Drift lies on the slope south of Greenland, where it has been formed under the influence of the Western Boundary Undercurrent (WBUC) closely downstream of its origin in the deep-water formation centres of the Nordic Seas. Therefore, the sediment record at Eirik Drift documents modifications in pathways and intensity of the WBUC. These modifications reflect alterations in deep-water formation in the Nordic Seas and are therefore coupled with climate changes. Based on the seismostratigraphic analysis of sedimentary architecture identified in a set of high-resolution seismic reflection data, we have reconstructed the palaeocirculation of the WBUC at Eirik Drift since the early Miocene. We revealed a strong WBUC during warm climate conditions, and in phases of climate cooling with enhanced sea-ice extent we interpreted weak WBUC influence. We suggest a southward shift of the deep-water formation regions along with a shift of the deep current system during the cool phases. This shift implies that the main North Atlantic deep-water route affected Eirik Drift only during warm phases and that during cool phases weak branches of the circulation system flowed over Eirik Drift.
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  • 19
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    The Holocene temperature conundrum (2014)
    National Academy of Sciences
    In:  EPIC3PNAS, National Academy of Sciences, 111(34), pp. E3501-E3505, ISSN: 0027-8424
    Details
    Publication Date: 2016-12-09
    Description: A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198–1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models.
    Repository Name: EPIC Alfred Wegener Institut
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  • 20
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    The Indian Ocean Zonal Mode over the past millennium in observed and modeled precipitation isotopes (2014)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 103, pp. 1-18, ISSN: 0277-3791
    Details
    Publication Date: 2014-10-17
    Description: The Indian Ocean Zonal Mode (IOZM) has gained considerable attention in the past decade due to its role in causing widespread flooding and droughts in the continents and islands surrounding the Indian Ocean. The IOZM has also been observed to vary on a low-frequency (multi-decadal) basis, making its behavior important to understand both for mid-range 21st century climate prediction and for paleoclimate studies. Despite efforts to reconstruct the IOZM using corals and other high-resolution proxies, nonstationarities in the response of paleoclimate proxies to the IOZM have also been noted, raising the possibility that the IOZM may be difficult to reconstruct or to predict in the long-term. It is therefore critical to assess the low-frequency component of the IOZM in observed, modeled, and paleoclimate data from the Indian Ocean region in order to identify nonstationary behavior and to assess its role in low-frequency climate variations. We present an analysis of low-frequency and nonstationary behavior in the IOZM on multi-decadal to centennial timescales using a combination of modeled, observed, and proxy reconstructions of δ18O/δDprecip. In order to assess multiple timescales of low-frequency variability, we focus on two key time periods: the historical period (1870–2003), and the past millennium (1000 C.E.-present). We find significant nonstationarities in the relationships between the IOZM, precipitation amount, and δ18Oprecip/δDprecip during the historical period. These relationships vary on a multi-decadal basis in our model and in observed/reanalysis datasets. Air-sea interactions in the Indo-Pacific Warm Pool and teleconnections to the Pacific Ocean, as well as the phase of the IOZM itself, may contribute to this nonstationary behavior. We examine the potential ramifications of nonstationary IOZM behavior using a synthesis of spatially distributed proxy archives of δ18Oprecip/δDprecip from both sides of the IOZM region spanning the past millennium. Our findings indicate that during the past millennium, a strong IOZM-like connection exists in the proxy data network, with anti-correlation between East Africa and Indonesia. However, the links are spatially limited and in some cases timescale-dependent. Nonlinear behaviors in these links suggest that the IOZM may be difficult to detect on a consistent basis in proxy records from the past millennium. Based on our modeling results, the inconsistent links in the IOZM proxy network may arise from temporally and spatially variable relationships between the IOZM, precipitation, and δ18Oprecip/δDprecip. We conclude that the IOZM's potential to influence the climate of the Indian Ocean region is inconsistently reflected in proxy data, and that due to the changing strength of the IOZM/δ18Oprecip/δDprecip relationship, its spatial “footprint” may be restricted on multi-decadal to multi-centennial timescales.
    Repository Name: EPIC Alfred Wegener Institut
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  • 21
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    On the difficulty of modeling Circumpolar Deep Water intrusions onto the Amundsen Sea continental shelf (2014)
    Elsevier
    In:  EPIC3Ocean Modelling, Elsevier, 84, pp. 26-34, ISSN: 1463-5003
    Details
    Publication Date: 2014-11-11
    Description: In the Amundsen Sea, warm Circumpolar Deep Water (CDW) intrudes onto the continental shelf and flows into the ice shelf cavities of the West Antarctic Ice Sheet, resulting in high basal melt rates. However, none of the high resolution global models resolving all the small ice shelves around Antarctica can reproduce a realistic CDW flow onto the Amundsen Sea continental shelf, and previous studies show simulated bottom potential temperature at the Pine Island Ice Shelf front of about −1.8 °C. In this study, using the Finite-Element Sea ice–ice shelf-Ocean Model (FESOM), we reproduce warm CDW intrusions onto the Amundsen Sea continental shelf and realistic melt rates of the ice shelves in West Antarctica. To investigate the importance of horizontal resolution, forcing, horizontal diffusivity, and the effect of grounded icebergs, eight sensitivity experiments are conducted. To simulate the CDW intrusion realistically, a horizontal resolution of about 5 km or smaller is required. The choice of forcing is also important and the cold bias in the NCEP/NCAR reanalysis over the eastern Amundsen Sea prevents warm CDW from intruding onto the continental shelf. On the other hand, the CDW intrusion is not highly sensitive to the strength of horizontal diffusion. The effect of grounded icebergs located off Bear Peninsula is minor, but may act as a buffer to an anomalously cold year.
    Repository Name: EPIC Alfred Wegener Institut
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  • 22
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    Uranium-Thorium Decay Series in the Oceans: Overview (2014)
    Elsevier
    In:  EPIC3Earth Systems and Environmental Sciences, (Reference Module in Earth Systems and Environmental Sciences), Amsterdam, Elsevier, 16 p., pp. 1-16, ISBN: 978-0-12-409548-9
    Details
    Publication Date: 2014-05-19
    Description: Natural radioactivity provides tracers in a wide range of characteristic timescales and reactivities, which can be used as tools to study the rate of reaction and transport processes in the ocean. Apart from cosmogenic nuclides and the long-lived radioisotope K-40, the natural radioactivity in the ocean is primarily derived from the decay series of three radionuclides that were produced in the period of nucleosynthesis preceding the birth of our solar system: Uranium-238, Thorium-232, and Uranium-235 (a fourth series, including Uranium-233, has already decayed away). The remaining activity of these so-called primordial nuclides in the Earth's crust, and the range of half-lives and reactivities of the elements in their decay schemes, control the present distribution of U-series nuclides in the ocean
    Repository Name: EPIC Alfred Wegener Institut
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  • 23
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    Monitoring glacier changes on the Antarctic Peninsula (2014)
    Springer
    In:  EPIC3Global Land Ice Measurements from Space, Berlin Heidelberg, Springer, pp. 717-741, ISBN: 978-3-540-79817-0
    Details
    Publication Date: 2016-11-15
    Description: The Antarctic Peninsula has exhibited some of the most spectacular changes observed in glacial systems in recent decades. The events include disintegration of ice shelves, acceleration and thinning of glaciers, variations in the limits between glacier facies, and retreat of glacier fronts. However, due to the lack of both consistent systematic observations of the glacial systems and information on their boundary conditions, it is difficult to accurately predict the contribution of Antarctic Peninsula glaciers to sea level rise and further responses of these ice masses to climatic and oceanographic changes. In this context, the activities of the GLIMS Regional Center for the Antarctic Peninsula and its network of international collaborators are based on the use of various types of Earth observation imagery, mainly optical and radar data. Although a complete glacier inventory is still lacking, we present the results of changes in glacier frontal positions and boundaries of glacier facies as well as links to dynamical adjustments for various locations in the Antarctic Peninsula’s ice masses. Evaluation of Advanced Spaceborne Thermal Emission and reflection Radiometer (ASTER) digital elevation models generated for the Antarctic Peninsula is also discussed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 24
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    Subfossil cladoceran from sediment in thermokarst lakes in northeastern Siberia, Russia and their relationship to limnological and climatic variables (2014)
    Springer
    In:  EPIC3Journal of Paleolimnology, Springer, 52(1), pp. 107-119
    Details
    Publication Date: 2016-10-22
    Repository Name: EPIC Alfred Wegener Institut
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  • 25
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    Ocean surface temperature variability: Large model-data differences at decadal and longer periods (2014)
    National Academy of Sciences
    In:  EPIC3Proceedings of the National Academy of Sciences, National Academy of Sciences, ISSN: 0027-8424
    Details
    Publication Date: 2017-02-08
    Description: The variability of sea surface temperatures (SSTs) at multidecadal and longer timescales is poorly constrained, primarily because instrumental records are short and proxy records are noisy. Through applying a new noise filtering technique to a global network of late Holocene SST proxies, we estimate SST variability between annual and millennial timescales. Filtered estimates of SST variability obtained from coral, foraminifer, and alkenone records are shown to be consistent with one another and with instrumental records in the frequency bands at which they overlap. General circulation models, however, simulate SST variability that is systematically smaller than instrumental and proxy-based estimates. Discrepancies in variability are largest at low latitudes and increase with timescale, reaching two orders of magnitude for tropical variability at millennial timescales. This result implies major deficiencies in observational estimates or model simulations, or both, and has implications for the attribution of past variations and prediction of future change.
    Repository Name: EPIC Alfred Wegener Institut
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  • 26
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    A 3D shear-wave velocity model of the upper mantle beneath China and the surrounding areas (2014)
    Elsevier
    In:  EPIC3Tectonophysics, Elsevier, 633, pp. 193-210, ISSN: 0040-1951
    Details
    Publication Date: 2014-12-02
    Description: We present a three-dimensional model of shear wave velocity for the upper mantle of China and the surrounding region by analyzing 50,338 vertical component multi-mode Rayleigh wave seismograms, recorded at 144 permanent and more than 300 temporary broadband stations in and around China. The procedure involves combination of 1-D path average models obtained by modeling each Rayleigh waveform up to the 4th higher mode in a tomographic inversion scheme. The dense station network and the use of multi-mode analysis help to achieve a lateral resolution of a few hundred kilometers down to 400 km depth. The seismic lithosphere, as it is defined by the crust and the high velocity mantle lid, is to the first order thin in east China and thick in the west, with a high velocity lid extending down to about 200 km depth beneath much of the Tibet–Pamir plateau. Beneath India, the thickness of the seismic lithosphere gradually increases from ~ 100 km in south India to more than 150 km in north India, where it underthrusts the Tibetan plateau to approximately the Jinsha River Suture. High velocity lid extending down to 100–150 km depth is also observed in the Tarim basin, Sichuan basin and Ordos block. In the eastern part of the North China craton the seismic lithosphere is probably close to or thinner than 70 km. Adjacent to these areas, the high velocity lid in the eastern Yangtze craton and South China fold system extends down to 70–80 km depth. A large-scale subhorizontal high velocity body is observed at depths of 150–350 km beneath the entire east China cratonic areas. This high velocity body might be the remnant of a delamination process which resulted in the decratonization of the North China and the Yangtze cratons.
    Repository Name: EPIC Alfred Wegener Institut
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  • 27
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    Anomalous South Pacific lithosphere dynamics derived from new total sediment thickness estimates off the West Antarctic margin (2014)
    Elsevier
    In:  EPIC3Global and Planetary Change, Elsevier, 123(Part A), pp. 139-149, ISSN: 0921-8181
    Details
    Publication Date: 2014-12-17
    Description: Paleotopographic models of the West Antarctic margin, which are essential for robust simulations of paleoclimate scenarios, lack information on sediment thickness and geodynamic conditions, resulting in large uncertainties. A new total sediment thickness grid spanning the Ross Sea–Amundsen Sea–Bellingshausen Sea basins is presented and is based on all the available seismic reflection, borehole, and gravity modeling data offshore West Antarctica. This grid was combined with NGDC's global 5 arc minute grid of ocean sediment thickness (Whittaker et al., 2013) and extends the NGDC grid further to the south. Sediment thickness along the West Antarctic margin tends to be 3–4 km larger than previously assumed. The sediment volume in the Bellingshausen, Amundsen, and Ross Sea basins amounts to 3.61, 3.58, and 2.78 million km3, respectively. The residual basement topography of the South Pacific has been revised and the new data show an asymmetric trend over the Pacific–Antarctic Ridge. Values are anomalously high south of the spreading ridge and in the Ross Sea area, where the topography seems to be affected by persistent mantle processes. In contrast, the basement topography offshore Marie Byrd Land cannot be attributed to dynamic topography, but rather to crustal thickening due to intraplate volcanism. Present-day dynamic topography models disagree with the presented revised basement topography of the South Pacific, rendering paleotopographic reconstructions with such a limited dataset still fairly uncertain.
    Repository Name: EPIC Alfred Wegener Institut
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  • 28
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    Escape performance of temperate king scallop, Pecten maximus under ocean warming and acidification (2014)
    Springer
    In:  EPIC3Marine Biology, Springer, 161(12), pp. 2819-2829, ISSN: 0025-3162
    Details
    Publication Date: 2015-01-16
    Description: Among bivalves, scallops are exceptional due to their capacity to escape from predators by swimming which is provided by rapid and strong claps that are produced by the phasic muscle interspersed with tonic muscle contractions. Based on the concept of oxygen and capacity-limited thermal tolerance, the following hypothesis was tested: ocean warming and acidification (OWA) would induce disturbances in aerobic metabolic scope and extracellular acid-case status and impair swimming performance in temperate scallops. Following longterm incubation under near-future OWA scenarios [20 vs. 10 °C (control) and 0.112 kPa CO2 (hypercapnia) vs. 0.040 kPa CO2 (normocapnic control)], the clapping performance and metabolic rates (MR) were measured in resting (RMR) and fatigued (maximum MR) king scallops, Pecten maximus, from Roscoff, France. Exposure to OA, either alone or combined with warming, left MR and swimming parameters such as the total number of claps and clapping forces virtually unchanged. Only the duration of the escape response was affected by OA which caused earlier exhaustion in hyper- than in normocapnic scallops at 10 °C. While maximum MR was unaffected, warm exposure increased RMR in both normocapnic and hypercapnic P. maximus resulting in similar Q10 values of ~2.2. The increased costs of maintenance and the observation of strongly reduced haemolymph PO2 levels indicate that at 20 °C scallops have reached the upper thermal pejus range with unbalanced capacities for aerobic energy metabolism. As a consequence, warming to 20 °C decreased mean phasic force during escape performance until fatigue. The observed prolonged recovery time in warm incubated scallops might be a consequence of elevated metabolic costs at reduced oxygen availability in the warmth.
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  • 29
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    Ocean-Bottom Seismometer (2014)
    Springer
    In:  EPIC3Encyclopedia of Earthquake Engineering, Encyclopedia of Earthquake Engineering, Berlin, Heidelberg, Springer, pp. 1-16, ISBN: 978-3-642-36197-5
    Details
    Publication Date: 2014-12-16
    Repository Name: EPIC Alfred Wegener Institut
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  • 30
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    Unraveling the geometry of the New England oroclines (eastern Australia): Constraints from magnetic fabrics (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The southern New England Orogen (NEO) in eastern Australia is characterized by tight curvatures (oroclines), but the exact geometry of the oroclines and their kinematic evolution are controversial. Here we present new data on the anisotropy ofmagnetic susceptibility (AMS), which provide a petrofabric proxy for the finite strain associated with the oroclines. We focus on a series of preoroclinal Devonian-Carboniferous fore-arc basin rocks, which are aligned parallel to the oroclinal structure, and by examining structural domains, we test whether or not the magnetic fabric is consistent with the strain axes. AMS data show a first-order consistency with the shape of the oroclines, characterized, in most of structural domains, by subparallelism between magnetic lineations, “structural axis” and bedding. With the exception of the Gresford and west Hastings domains, our results are relatively consistent with the existence of the Manning and Nambucca (Hastings) Oroclines. Reconstruction of magnetic lineations to a prerotation (i.e., pre–late Carboniferous) stage, considering available paleomagnetic results, yields a consistent and rather rectilinear NE-SW predeformation fore-arc basin. This supports the validity of AMS as a strain proxy in complex orogens, such as the NEO. In the Hastings Block, magnetic lineations are suborthogonal to bedding, possibly indicating a different deformational history with respect to the rest of the NEO.
    Description: Published
    Description: 2261–2282
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: AMS data, magnetic fabric, oroclines ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.07. Tectonophysics::04.07.01. Continents ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Paleomagnetism and magnetic fabric of the Eastern Cordillera of Colombia: Evidence for oblique convergence and non rotational reactivation of a Mesozoic intracontinental rift (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We report the paleomagnetic and magnetic fabric results of 58 sites from Cretaceous-Miocene marine and continental strata from the Eastern Cordillera (EC) and the Cucuta zone, at the junction between the Santander Massif and the Merida Andes of Colombia. The EC is an intracontinental doubly vergent range inverting a Triassic to Early Cretaceous rift zone. Twenty-three sites reveal nonsystematic tectonic rotations, including unrotated areas of the EC range with respect to stable South America. Our data show that the EC inverted a NNE oriented rift zone and that the orientation of the Mesozoic rift and the mountain chain roughly correspond. Interestingly, magnetic lineations from anisotropy of magnetic susceptibility analysis do not trend parallel to the chain but rather are oblique to the main orogenic trend. By also considering GPS evidence of a ~1 cm/yr ENE displacement of central western Colombia accommodated by the EC, we suggest that the Miocene-Recent deformation event of this belt arises from ENE oblique convergence reactivating a NNE oriented rift zone. Oblique shortening was likely partitioned into pure dip-slip shear characterizing thick-skinned frontal thrust sheets (well known along both chain fronts) and by range-parallel right-lateral strike-slip faults, which have not been identified yet, but likely exist in the axial part of the EC. Finally, the 35° ± 9° clockwise rotation observed in four post-Miocene magnetically overprinted sites from the Cucuta zone reflects late Cenozoic and ongoing right-lateral strike-slip displacement occurring along faults parallel to the Boconó fault system, possibly connected with the right-lateral faults inferred to exist along the axial part of the EC.
    Description: Published
    Description: 2233–2260
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Paleomagnetism, magnetic fabric, Eastern Cordillera ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    An analysis of tropical instability waves in a numerical model of the Pacific Ocean - 1. Spatial variability of the waves (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Unstable oscillations confined within the mixed layer close to the equator are generated in wind-forced experiments performed in a multilevel general circulation model configured for the tropical Pacific Ocean. The experiments indicate that the waves develop preferentially in the eastern Pacific along the northern temperature front. However, there is clear evidence of a second unstable region along the southern temperature front in the central Pacific. In both regions the instabilities propagate westward, but in the central Pacific their phase speed is considerably smaller. The differences between the wave characteristics in the eastern and central Pacific are closely correlated to the differences in the time mean conditions of the flow. The eastern instabilities have a structure with two peaks in amplitude: one located on the equator and the other a few degrees north of it. Their dispersion characteristics show many similarities to those of tropical instability waves (TIWs) observed in the Pacific Ocean, while the instabilities which grow in the central Pacific do not have any known observed correspondents. We explore the spatial variability of the simulated waves through a wavelet analysis, which provides detailed results on how the period and wavelength of the instabilities change as a function of longitude, latitude, and depth. The wavelet analysis reveals that in the eastern Pacific and close to the surface the TIWs have a phase speed of-48 cm/s, while in the central Pacific they have a phase speed of-11 cm/s. In particular, the change in the phase speed is due to a change in the dominant period of the TIWs: The period of the central Pacific instabilities is considerably longer than the period of the instabilities present in the eastern Pacific.
    Description: This work was supported by the Department of Commerce/NOAA grant NA56GP0026. One of the authors (SM) was partially supported by a NASA Global Change Fellowship NGT-30288.
    Description: Published
    Description: 29613-29635
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: Ocean modeling ; Equatorial Ocean ; Tropical Instability Waves ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling
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  • 33
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    Analysis of Lava Flow Effusion Rate Using High Spatial Resolution Infrared Data (2014)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Remote sensing thermal data of active lava flows allow for the evaluation of instantaneous effusion rates. This is made possible by simple formulae relating the lava effusion rate to the power energy radiated per unit time from the surface to the flow. Such formulae are based on a specific flow model and, consequently, their validity is subject to the model assumptions. The most questionable assumption is probably the constancy of the surface temperature. Herein, we use high spatial resolution infrared data to demonstrate the existence of an underlying relationship between the surface temperature and the lava flow thickness, using the 2001 Mt. Etna flow as a case study. According to this relationship, observed changes in surface temperature does not represent a weakness of the model but is the expected consequence of actual variations in the topographic down flow profile.
    Description: Published
    Description: 391-408
    Description: 3V. Dinamiche e scenari eruttivi
    Description: restricted
    Keywords: Remote sensing, effusion rate, heat flux, Etna, MIVIS ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 34
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    Intensity of the geomagnetic field in Europe for the last 3 ka: Influence of data quality on geomagnetic field modeling (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: One of the main challenges of paleomagnetic research is to obtain high-resolution geomagnetic field intensity reconstructions. For the last millennia, these reconstructions are mostly based on archeomagnetic data. However, the quality of the intensity data available in the databases is very variable, and the high scatter observed in the records clearly suggests that some of them might not be reliable. In this work we investigate how the geomagnetic field intensity reconstructions and, hence, our present knowledge of the geomagnetic field in the past, are affected by the quality of the data selected for modeling the Earth’s magnetic field. For this purpose we rank the European archeointensity data in four quality categories following widely accepted paleomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens retained to calculate the mean intensities. Four geomagnetic field regional models have been implemented by applying the revised spherical cap harmonic analysis to these four groups of input data. Geomagnetic field models strongly depend on the used data set. The model built using all the available data (without any preselection) appears to be the less accurate, indicating some internal inconsistencies of the data set. In addition, some features of this model are clearly dominated by the less reliable archeointensity data, suggesting that such features might not reflect real variations of the past geomagnetic field. On the contrary, the regional model built on selected high-quality intensity data shows a very consistent intensity pattern at the European scale, confirming that the main intensity changes observed in Europe in the recent history of the geomagnetic field occurred at the continental scale.
    Description: Published
    Description: 2515–2530
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: Geomagnetism ; Paleomagnetism ; Archeomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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  • 35
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    Long-time variation of soil CO2 fluxes at the summit crater of Vulcano (Italy) (2014)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Here, we report the first continuous data of geochemical parameters acquired directly from the active summit crater of Vulcano. This approach provides a means to better investigate deep geochemical processes associated with the degassing system of Vulcano Island. In particular, we report on soil CO2 fluxes from the upper part of Vulcano, a closed-conduit volcano, from September 2007 to October 2010. Large variations in the soil CO2 and plume SO2 fluxes (order of magnitude), coinciding with other discontinuous geochemical parameters (CO2 concentrations in fumarole gas) and physical parameters (increase of shallow seismic activity and fumarole temperatures) have been recorded. The results from this work suggest new prospects for strengthening geochemical monitoring of volcanic activity and for improving the constraints in the construction of a “geochemical model”, this being a necessary condition to better understand the functioning of volcanic systems.
    Description: Published
    Description: 1859-1863
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 5V. Sorveglianza vulcanica ed emergenze
    Description: 1R. Reti di monitoraggio e Osservazioni
    Description: JCR Journal
    Description: restricted
    Keywords: Vulcano Island ; Geochemical monitoring ; CO2 flux ; CO2 fumaroles ; SO2 flux ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 36
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    Effects of Flow Volume and Grain Size on Mobility of Granular Flows of Angular Rock Fragments (2014)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Laboratory experiments have shown that the finer the grain size of granular flows of angular rock fragments (all the other features the same), the more mobile their centre of mass. This is due to the fact that the finer the grain size, the larger the number of particles in the flow so that their agitation due to the interaction with the subsurface asperities has a smaller penetration within the flow. The smaller the agitation of the particles per unit of flow mass, the smaller the energy dissipated per unit of travel distance. Also, the larger the flow volume, the smaller the mobility of its centre of mass. This is due to the fact that a deposit accretes backward during its deposition on a slope change. However, the frontal end of a larger-volume deposit is more distal than that of a smaller-volume deposit because the larger the volume, the larger its longitudinal spreading.
    Description: Published
    Description: 1621-1624
    Description: 3V. Dinamiche e scenari eruttivi
    Description: restricted
    Keywords: Pyroclastic Flows ; Mobility ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 37
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    Ultra-thick Triassic dolomites control the rupture behavior of the central Apennine seismicity: Evidence from magnetic modeling of the L’Aquila fault zone (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: High-resolution tomography from the 2009 L’Aquila extensional seismic sequence has shown that the Mw 6.1 main shock and most of the aftershocks occurred within a high velocity body (6.6≤Vp≤6.8 Km/s), located between depths of 3 and 12 km. The nature of the high Vp-body has remained speculative, although exhumed mafic deep crustal and upper mantle rocks (serpentinites) have been favoured. We used 3D magnetic anomaly modelling to investigate the plausibility of these favoured sources for the L’Aquila body. The modelling does not support the presence of high-velocity serpentinites with a 30-50% serpentinization degree and gabbros. Accordingly, we conclude that the high Vp-body may represent non-magnetic upper Triassic and possibly lower Liassic dolomites that have been drilled in neighbouring wells for 2-4 km. This conclusion is also consistent with the lack of a coherent gravity anomaly for the body. We speculate that ultra-thick Triassic dolomites reaching a thickness of 8 km may have been deposited in syntectonic wedges formed at the northern margin of the Ionian Sea, where oceanic spreading occurred in mid-late Triassic times.
    Description: Published
    Description: 6756–6770
    Description: 7A. Geofisica di esplorazione
    Description: JCR Journal
    Description: restricted
    Keywords: L’Aquila earthquake ; seismic tomography ; magnetic anomalies ; magnetic modelling ; dolomites; ; Apennines ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies
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  • 38
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    Real-time measurements of the concentration and isotope composition of atmospheric and volcanic CO2 at Mount Etna (Italy) (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: We present unprecedented data of real-time measurements of the concentration and isotope composition of CO2 in air and in fumarole-plume gases collected in 2013 during two campaigns at Mount Etna volcano, which were made using a laser-based isotope ratio infrared spectrometer. We performed approximately 360 measurements/h, which allowed calculation of the δ13C values of volcanic CO2. The fumarole gases of Torre del Filosofo (2900mabove sea level) range from 3.24 ± 0.06‰to 3.71 ± 0.09‰, comparable to isotope ratio mass spectrometry (IRMS) measurements of discrete samples collected on the same dates. Plume gases sampled more than 1 km from the craters show a δ13C= 2.2 ± 0.4‰, in agreement with the crater fumarole gases analyzed by IRMS. Measurements performed along ~17km driving track from Catania to Mount Etna show more negative δ13C values when passing through populated centers due to anthropogenic-derived CO2 inputs (e.g., car exhaust). The reported results demonstrate that this technique may represent an important advancement for volcanic and environmental monitoring.
    Description: Published
    Description: 2382–2389
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Real-time data of CO2 content and δ13C in atmospheric/volcanic gases ; This study opens new perspective for the community for volcanic surveillance ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 39
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    The failed eruption of Mt. Etna in December 2005: evidence from volcanic tremor analyses (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Strong changes in seismic radiation, comparable to those preceding and/or accompanying eruptive activity in recent years, were recorded at Mt. Etna volcano, Italy, from November 2005 to January 2006. The amplitude of volcanic tremor peaked in mid-December 2005 after a continuous, slow increase from August 2005 onwards, during which neither effusive nor paroxysmal activity was observed by volcanologists and alpine guides. During this time span, the centroid locations of volcanic tremor moved towards the surface, more and more clustered below the summit craters. The application of pattern classification analysis based on Self-Organizing Maps and fuzzy clustering to volcanic tremor data highlighted variations in the frequency domain as well. These changes were temporally associated with ground deformation variations, as indicative of a mild inflation of the summit of the volcano, and with a conspicuous increase in the SO2 plume-flux emission. Overall, we interpret this evidence as the result of recharging of the volcanic feeder at depth (〉 3 km below sea level) during which magma did not reach the shallow plumbing system.
    Description: Published
    Description: 4989–5005
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: embargoed_20140606
    Keywords: time series analysis ; volcano seismology ; volcano monitoring ; neural network and fuzzy logic ; seismic tomography ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 40
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    Probabilistic modeling of future volcanic eruptions at Mount Etna (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The statistical analysis of volcanic activity at Mt Etna was conducted with the twofold aim of (1) constructing a probability map for vent opening of future flank eruptions and (2) forecasting the expected number of eruptive events at the summit craters. The spatiotemporal map of new vent opening at Etna volcano is based on the analysis of spatial locations and frequency of flank eruptions starting from 1610. Thanks to the completeness and accuracy of historical data over the last four centuries, we examined in detail the spatial and temporal distribution of flank eruptions showing that effusive events follow a nonhomogenous Poisson process with space-time varying intensities. After demonstrating the spatial nonhomogeneity and the temporal nonstationarity of flank eruptions at Etna, we calculated the recurrence rates (events expected per unit area per unit time) and produced different spatiotemporal probability maps of new vent opening in the next 1, 10 and 50 years. These probabilistic maps have an immediate use in evaluating the future timing and areas of Etna prone to volcanic hazards. Finally, the results of the analysis of the persistent summit activity during the last 110 years indicate that the hazard rate for eruptive events is not constant with time, differs for each summit crater of Mt Etna, highlighting a general increase in the eruptive frequency starting from the middle of last century and particularly from 1971, when the SE crater was formed.
    Description: This work was developed in the frame of the TecnoLab, the Laboratory for the Technological Advance in Volcano Geophysics organized by INGV-CT, DIEES-UNICT, and DMI-UNICT.
    Description: Published
    Description: 1925-1935
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 3IT. Calcolo scientifico e sistemi informatici
    Description: JCR Journal
    Description: restricted
    Keywords: Etna ; probabilistic modeling ; eruption ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.02. Cellular automata, fuzzy logic, genetic alghoritms, neural networks ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 41
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    Ocean, sea-ice, atmosphere oscillations in the Southern Ocean as simulated by the SINTEX coupled model (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: 1This study evaluates the Antarctic Circumpolar Wave (ACW) as simulated by the SINTEX coupled model. We found evidence that sea-ice treatment plays a crucial role on simulating the ACW. In particular, SST anomalies at interannual time scales describe a propagating ACW-like pattern when a dynamic thermodynamic sea-ice model is coupled with the ocean, but when sea-ice is relaxed to climatology, anomalies occur as zonally symmetric patterns that do not propagate in longitude. Moreover, from the experiment with an active sea-ice component we saw that ACW-like oscillations are strongly modulated by low frequency variability. Our result adds some extra confidence to previous studies based on relatively short series of observed data.
    Description: This research was supported by the PREDICATE EU project (EVK2 – CT-1999 – 0020,). First author was supported by the PRISM EU project (EVR1 – CT-2001 – 40012).
    Description: Published
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: Antarctic Circumpolar Wave ; General Circulation Models ; air-ice-sea interactions ; 02. Cryosphere::02.04. Sea ice::02.04.01. Atmosphere/sea ice/ocean interaction
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 42
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    An analysis of tropical instability waves in a numerical model of the Pacific Ocean - 2. Generation and energetics of the waves (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The instability processes which generate unstable waves with chara- cteristics similar to observed tropical instability waves in the Pacific Ocean are examined through a local energy analysis based on deviations from the time mean flow. Numerical experiments indicate that the waves develop preferentially in the eastern Pacific along the northern temperature front and have a westward phase speed and a structure with two peaks in amplitude: one located on the equator and the other a few degrees north of it. The energy analysis shows that the "two-peak" structure of the eastern waves is explained by two different instability processes which occur at different latitudes. In the time mean sense the region north of the equator is baroclinically unstable, while barotropic instability prevails at the equator. The life cycle of the waves is revealed by the time evolution of the energetics. Baroclinic instability is the dominant triggering mechanism which induces growth of the waves along the northern temperature front. The eddy pressure fluxes radiate energy south of the equator where the rneridional shear between the Equatorial Undercurrent and the South Equatorial Current becomes barotropically unstable. From the numerical simulations, there is evidence of a second unstable region in the central Pacific south of the equator where the instabilities have a lower phase speed. The energy analysis also shows that these waves grow from both barotropic and baroclinic conversions.
    Description: This work was supported by the Department of Com- merce/NOAA under grant NA56GP0026. One of the au- thors (SM) was partially supported by a NASA Global Change Fellowship NGT-30288. Another author (AB) was supported by a UCAR Postdoctoral Fellowship
    Description: Published
    Description: 29637-29661
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: Ocean modeling ; Equatorial Ocean ; Tropical Instability Waves ; Ocean wave generation ; Ocean wave energetics ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling
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  • 43
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    Seismo-tectonic behavior of the Pernicana Fault System (Mt Etna): A gauge for volcano flank instability? (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Flank instability at basaltic volcanoes is often related to repeated dike intrusions along rift zones and accompanied by surface fracturing and seismicity. These processes have been mostly studied during specific events, and the lack of longer-term observations hinders their better understanding. Here we analyze ~20 years of deformation of the Pernicana Fault System (PFS), the key structure controlling the instability of the eastern flank of Mt. Etna. We exploit East-West and vertical components of mean deformation velocity, as well as corresponding time series, computed from ERS/ENVISAT (1992–2010) and COSMO-SkyMed (2009–2011) satellite radar sensors via Synthetic Aperture Radar Interferometry techniques. We then integrate and compare this information with field, seismic, and leveling data, collected between 1980 and 2012. We observe transient displacements accompanied by seismicity, overprinted on a long-term background eastward motion (~2 cm/yr). In the last decades, these transient events were preceded by a constant amount of accumulated strain near the PFS. The time of strain accumulation varies between a few years and a few decades, also depending on magma emplacement within the nearby North East Rift, which may increase the strain along the PFS. These results suggest that the amount of deformation near the PFS may be used as a gauge to forecast the occurrence of instability transients on the eastern flank of Etna. In this context, the PFS may provide an ideal, small-scale structure to test the relations between strain accumulation, stress loading, and seismic energy release.
    Description: This work has been partially supported by the Italian Space Agency (ASI) within the SAR4Volcanoes project, agreement I/ 034/11/0.
    Description: Published
    Description: 4398-4409
    Description: 1T. Geodinamica e interno della Terra
    Description: 2T. Tettonica attiva
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: 5T. Sorveglianza sismica e operatività post-terremoto
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: JCR Journal
    Description: restricted
    Keywords: Volcano flank instability ; Pernicana fault ; Etna ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
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  • 44
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    Complete seismic release of tectonic strain and earthquake recurrence in the Apennines (Italy) (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Here I compare estimates of tectonic strain rates from dense Global Positioning System measurements with the seismicity released in the last ~500 years in the Apennines (Italy). The rates of seismic moment accumulation from geodesy and of historical seismic release by earthquakes agree within the uncertainties, ruling out significant aseismic deformation. Within the considered 400 km long section of the Apennines, this balance yields an average recurrence interval of 30–75 years for MW≥6.5 events without requiring a future earthquake larger than those observed historically (MW~7). A minimum estimate of unreleased strain allows MW≥6.5 and MW≥6.9 events to be released in ~35% and ~10% of the central-southern Apennines, respectively. The definition of the seismic potential for smaller events is more uncertain, and their occurrence remains a significant threat throughout the Apennines.
    Description: Published
    Description: 1155–1162
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Crustal deformation ; Earthquakes ; GPS ; Apennines ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
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  • 45
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    Long-term stress-strain analysis of volcano flank instability: The eastern sector of Etna from 1980 to 2012 (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigated the evolution of seismicity and deformation in the unstable eastern flank of Etna volcano over a 30 year period (from 1980 to 2012). A significant temporal correlation has been revealed between periods of flank acceleration and intensified seismic activity by comparing seismicity along the northern border (Pernicana fault system) of the sliding flank and the deformation of the eastern flank. Two marked phases have been observed in 1984-1986 and in the years following 2002. These two phases are separated by an intermediate phase from 1987 to 2001, in which the flank sliding slowed down and the seismicity dropped drastically. This common temporal evolution in the deformation rate and seismic release supports the hypothesis that the seismicity in the northern border can be viewed as a marker of the response to accommodate the stress exerted by the traction of the eastern flank sliding. This interplay has also been corroborated by finite element method numerical computations that highlight a good correlation between the seismicity pattern and areas of positive stress changes induced by the sliding surface. The two intense phases of flank acceleration are representative of two main different sources: volcano flank instability stretching the eastern sector in the first 1984-1986 phase and magmatic intrusions pushing the eastern flank seaward since the 2002-2003 eruption. Establishing the relationship between flank acceleration and seismic activation therefore contributes to understanding Etna's mechanical behavior and provides insights into the processes regulating the unstable flank response.
    Description: Published
    Description: 5098-5108
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: JCR Journal
    Description: restricted
    Keywords: Pernicana ; fault ; volcano-tectonics ; flank instability ; seismicity and deformation ; stress and strain ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
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  • 46
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    Magma flow between summit and Pu‘u ‘O‘o at Kılauea Volcano, Hawai‘i (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Volcanic eruptions are often accompanied by spatiotemporal migration of ground deformation, a consequence of pressure changes within magma reservoirs and pathways. We modeled the propagation of pressure variations through the east rift zone (ERZ) of K" ılauea Volcano, Hawai‘i, caused by magma " o-Kupaianaha withdrawal during the early eruptive episodes (1983–1985) of the ongoing Pu‘u ‘ O‘" " eruption. Eruptive activity at the Pu‘u ‘ O‘" o vent was typically accompanied by abrupt deflation that lasted for several hours and was followed by a sudden onset of gradual inflation once the eruptive episode had ended. Similar patterns of deflation and inflation were recorded at K" ılauea’s summit, approximately 15 km to the northwest, albeit with time delays of hours. These delay times can be reproduced by modeling the spatiotemporal changes in magma pressure and flow rate within an elastic-walled dike that traverses K" ılauea’s ERZ. Key parameters that affect the behavior of the magma-dike system are the dike dimensions, the elasticity of the wall rock, the magma viscosity, and to a lesser degree the magnitude and duration of the pressure variations themselves. Combinations of these parameters define a transport efficiency and a pressure diffusivity, which vary somewhat from episode to episode, resulting in variations in delay times. The observed variations in transport efficiency are most easily explained by small, localized changes to the geometry of the magma pathway
    Description: Published
    Description: 2232–2246
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: magma flow ; dikes ; Kilauea ; elastic rock ; magma-rock coupling ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 47
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    The coupling between very long period seismic events, volcanic tremor, and degassing rates at Mount Etna volcano (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: From December 2005 to January 2006, an anomalous degassing episode was observed at Mount Etna, well-correlated with an increase in volcanic tremor, and in the almost complete absence of eruptive activity. In the same period, more than 10,000 very long period (VLP) events were detected. Through moment tensor inversion analyses of the VLP pulses, we obtained quantitative estimates of the volumetric variations associated with these events. This allowed a quantitative investigation of the relationship between VLP seismic activity, volcanic tremor, and gas emission rate at Mount Etna. We found a statistically significant positive correlation between SO2 gas flux and volcanic tremor, suggesting that tremor amplitude can be used as a first-order proxy for the background degassing activity of the volcano. VLP volumetric changes and SO2 gas flux are correlated only for the last part of our observations, following a slight change in the VLP source depth. We calculate that the gas associated with VLP signal genesis contributed less than 5% of the total gas emission. The existence of a linear correlation between VLP and degassing activities indicates a general relationship between these two processes. The effectiveness of such coupling appears to depend upon the particular location of the VLP source, suggesting that conduit geometry might play a significant role in the VLP-generating process. These results are the first report on Mount Etna of a quantitative relationship between the amounts of gas emissions directly estimated through instrumental flux measurements and the quantities of gas mass inferred in the VLP source inversion.
    Description: Published
    Description: 4910-4921
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Very Long Period seismicity ; UV scanners network ; Etna Volcano ; volcano monitoring ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 48
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    Interaction between magma intrusion and flank dynamics at Mt. Etna in 2008, imaged by integrated dense GPS and DInSAR data (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Global positioning system (GPS) and differential interferometric synthetic aperture radar (DInSAR) data, collected from July 2007 to July 2008 on Mt. Etna, are analyzed to define the dynamics preceding and accompanying the onset of the eruption on 13 May 2008. Short- and long-term comparisons have been made on both GPS and radar data, covering similar time windows. Thanks to the availability of three GPS surveys the year before the eruption onset, an increase in the seaward movement of the NE flank of the volcano has been detected in the few months before the dike intrusion. The GPS ground deformation pattern also shows a slight inflation centered on the western side of the volcano in the preeruptive long-term comparison (from July 2007 to May 2008). The GPS has been integrated with DInSAR data by the SISTEM approach, to take advantage of the different methodologies and provide high spatial sampling of the 3-D ground displacement pattern. We inverted the SISTEM results to model the pressure source causing the observed preeruptive inflation. The subsequent emplacement of the eruptive dike was imaged by two GPS surveys carried out on a dense network over the uppermost part of the volcano on 6 and 13 May, i.e., a few days before and a few hours after the beginning of the eruption. We inverted this comparison to define the position, geometry, and kinematics of the dike. The dike intrusion was also imaged by DInSAR data with temporal baselines of 2-3 months, which confirm strong displacements localized on the summit area, rapidly decreasing toward the middle flanks of the volcano, as detected by very short-term GPS data; furthermore, the comparison between DInSAR and GPS data highlighted the presence of a depressurizing source localized beneath the upper southwestern area, acting just after the dike intrusion. Finally, the long-period (1 year) GPS and DInSAR data were integrated by SISTEM to finely depict the 3-D ground deformation pattern with the highest spatial resolution. The long-period data allowed the complex kinematics of the volcano to be finely imaged and highlighting the interaction between flank dynamics and magma injection.
    Description: Published
    Description: 2818-2835
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: flank dynamics ; eruption ; volcano-tectonics ; GPS ; DInSAR ; data integration ; Etna ; deformation ; volcano ; fault ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 49
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    New data from borehole strainmeters to infer lava fountain sources (Etna 2011-2012) (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In January 2011 eruptive activity resumed at Etna producing a new phase with frequent lava fountain episodes until April 2012. In November 2011, the first two borehole strainmeters were installed, which detected negative strain changes (~ 0.15 - 0.8 strain) during the paroxysmal events. A Finite Element Model was set up to estimate accurately the tilt and volumetric strain, taking into account the real profile of the volcano and the elastic medium heterogeneity. The numerical computations indicated an elongated depressurizing source located at 0 km b.s.l., which underwent a volume change of ~2 x 106 m3 which is the most of the magma volume erupted while a smaller remaining part is accommodated by the magma compressibility. This shallow source cannot accumulate large magma volumes and, thus, favours short term periodic eruptive events with a fairly constant balance between the refilling and the erupted magma.
    Description: Published
    Description: 3579-3584
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: embargoed_20150613
    Keywords: Etna volcano ; lava fountain eruptions ; shallow plumbing system ; borehole strainmeters ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 50
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    Interseismic coupling, seismic potential, and earthquake recurrence on the southern front of the Eastern Alps (NE Italy) (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Here we use continuous GPS observations to document the geodetic strain accumulation across the South-Eastern Alps (NE Italy). We estimate the interseismic coupling on the intracontinental collision thrust fault and discuss the seismic potential and earthquake recurrence. We invert the GPS velocities using the back slip approach to simultaneously estimate the relative angular velocity and the degree of interseismic coupling on the thrust fault that separates the Eastern Alps and the Venetian-Friulian plain. Comparison between the rigid rotation predicted motion and the shortening observed across the area indicates that the South-Eastern Alpine thrust front absorbs about 70% of the total convergence between the Adria and Eurasia plates. The coupling is computed on a north dipping fault following the continuous external seismogenic thrust front of the South-Eastern Alps. The modeled thrust fault is currently locked from the surface to a depth of ≈10 km. The transition zone between locked and creeping portions of the fault roughly corresponds with the belt of microseismicity parallel and to the north of the mountain front. The estimated moment deficit rate is 1.3 ± 0.4 × 1017 Nm/yr. The comparison between the estimated moment deficit and that released historically by the earthquakes suggests that to account for the moment deficit the following two factors or their combination should be considered: (1) a significant part of the observed interseismic coupling is released aseismically and (2) infrequent “large” events with long return period (〉 1000 years) and with magnitudes larger than the value assigned to the largest historical events (Mw≈ 6.7).
    Description: Published
    Description: 4448-4468
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Eastern Alps; interseismic coupling; seismotectonics; seismic potential; recurrence time; GPS ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 04. Solid Earth::04.07. Tectonophysics::04.07.01. Continents ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 51
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    An active oblique-contractional belt at the transition between the Southern Apennines and Calabrian Arc: The Amendolara Ridge, Ionian Sea, Italy (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: High-resolution, single-channel seismic and multibeam bathymetry data collected at the Amendolara Ridge, a key submarine area marking the junction between the Apennine collision belt and the Calabrian subduction forearc, reveal active deformation in a supposedly stable crustal sector. New data, integrated with existing multichannel seismic profiles calibrated with oil-exploratory wells, show that middle to late Pleistocene sediments are deformed in growth folds above blind oblique-reverse faults that bound a regional pop-up. Data analysis indicates that ~10 to 20 km long banks that top the ~80 km long, NW-SE trending ridge are structural culminations above en echelon fault segments. Numeric modeling of bathymetry and stratigraphic markers suggests that three 45° dipping upper crustal (2–10 km) fault segments underlie the ridge, with slip rates up to ~0.5 mm/yr. Segments may be capable with M ~ 6.1–6.3 earthquakes, although an unknown fraction of aseismic slip undoubtedly contributes to deformation. The fault array that bounds the southern flank of the ridge (Amendolara Fault System) parallels a belt of Mw 〈 4.7 strike-slip and thrust earthquakes, which suggest current left-oblique reverse motion on the array. The eastern segment of the array shows apparent morphologic evidence of deformation and might be responsible for Mw ≤ 5.2 historic events. Late Pliocene-Quaternary growth of the oblique contractional belt is related to the combined effects of stalling of Adriatic slab retreat underneath the Apennines and subduction retreat of the Ionian slab underneath Calabria. Deformation localization was controlled by an inherited mechanical interface between the thick Apulian (Adriatic) platform crust and the attenuated Ionian Basin crust.
    Description: Published
    Description: 2169–2194
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: Active compression ; Growth strata modeling ; High-resolution seismic ; Multibeam bathymetry ; Jonian Sea ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
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  • 52
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    Wave-guide effects in very high rate GPS record of the 6 April 2009, Mw 6.1 L'Aquila, central Italy earthquake (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: A 10 Hz sampling frequency GPS station was installed near L'Aquila a few days before the 6 April 2009 Mw 6.1 earthquake. It recorded displacement waveforms during the main shock and the largest Mw 5.4 aftershock of 7 April. The horizontal components of the main shock contain a high-amplitude (43 cm peak-to-peak) nearly harmonic (1 Hz) wave train not evident in other nearby instrumental records. The persistency of this feature during aftershocks recorded by a temporarily colocated seismological station highlights a local site effect. Traditional models based on near-surface velocity structure and topography variations fail to reproduce the size and frequency band of the observed amplified motion. The amplified wave train can be explained by a low-velocity fault zone layer below the station. This model fits the delay of the large-amplitude nearly harmonic wave train after the S wave phase and is consistent with the variation in the fault excitation efficiency between the two shocks in relation to their different source depth and location. Synthetic calculation of trapped waves in a model consisting of two quarter spaces separated by a 650 m wide low-velocity zone with 50% velocity reduction and Q value of 20 fit well the observed anomalous record. The parameters of the model fault zone layer are consistent with geological evidence of a broad damage zone adjacent to the station and a similar site response found in this crustal zone with ambient noise. Results of shallow seismic surveys and sonic logs from deep wells provide independent constraints on the host rock velocities.
    Description: This work has partially benefited from the activities performed in the NERA project (Network of European Research infrastructures for earthquake risk Assessment and mitigation, 262330), funded by the European Commission FP7 program, and in the FIRB-Abruzzo project, funded by the Italian Ministery of Education, University and Research.
    Description: Published
    Description: 490–501
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: High-rate GPS ; Transient deformation ; L'Aquila earthquake ; fault-guided waves ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 53
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    Investigation of the complex dynamics and structure of the 2010 Eyjafjallajökull volcanic ash cloud using multispectral images and numerical simulations (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigated the structure and evolution of the 2010 Eyjafjallajökull volcanic cloud and its dispersal over Iceland and Europe integrating satellite multispectral images and numerical simulations. Data acquired by Medium Resolution Imaging Spectrometer (MERIS)and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) have been analyzed to quantify the cloud extent and composition. The VOL-CALPUFF dispersal code was applied to reconstruct the transient and 3-D evolution of the cloud. Source parameters estimated on the base of available a posteriori volcanological data sets have been used. Quantitative comparisons between satellite retrievals and modeling results were performed for two selected instants of time during the first and third eruptive phases on a regional scale. Sensitivity of the model to initial volcanological conditions has been analyzed at continental scale. Several complex non intuitive features of cloud dynamics have been highlighted and strengths and limitations of the adopted methods identified. The main findings are: the level of quantitative agreement between satellite observations and numerical results depends on ash cloud composition (particle sizes and concentration) with better agreement for smaller particles and higher concentrations; the agreement between observations and modeling outcomes also depends on the temporal stability of volcanological conditions and the complexity of the meteorological wind field; the irregular dispersion of ash, as reconstructed from satellite data and numerical modeling, can be well explained by the different response of particle sizes to strong vertical wind-shear, and by resuspension processes acting at ground level; eruptive source conditions are the main source of uncertainty in modeling, especially during an ongoing crisis and at long-range scales.
    Description: Published
    Description: 4729–4747
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Volcanic ash cloud ; Satellite retrieval ; Numerical modelling ; Eyjafjallajokull ; Ash dispersal and deposition ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
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  • 54
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    Vertical GPS ground motion rates in the Euro-Mediterranean region: New evidence of velocity gradients at different spatial scales along the Nubia-Eurasia plate boundary (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We use 2.5 to 14 years long position time series from 〉800 continuous Global Positioning System (GPS) stations to study vertical deformation rates in the Euro-Mediterranean region. We estimate and remove common mode errors in position time series using a principal component analysis, obtaining a significant gain in the signal-to-noise ratio of the displacements data. Following the results of a maximum likelihood estimation analysis, which gives a mean spectral index ~ 0.7, we adopt a power law + white noise stochastic model in estimating the final vertical rates and find 95% of the velocities within ±2 mm/yr, with uncertainties from filtered time series ~40% smaller than from the unfiltered ones. We highlight the presence of statistically significant velocity gradients where the stations density is higher. We find undulations of the vertical velocity field at different spatial scales both in tectonically active regions, like eastern Alps, Apennines, and eastern Mediterranean, and in regions characterized by a low or negligible tectonic activity, like central Iberia and western Alps. A correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area. Glacial isostatic adjustment and weathering processes do not completely explain the measured rates, and a combination of active tectonics and deep-seated geodynamic processes must be invoked. Excluding areas where localized processes are likely, or where subduction processes may be active, mantle dynamics is the most likely process, but regional mantle modeling is required for a better understanding.
    Description: Published
    Description: 6003–6024
    Description: 1T. Geodinamica e interno della Terra
    Description: 2T. Tettonica attiva
    Description: 1R. Reti di monitoraggio e Osservazioni
    Description: JCR Journal
    Description: restricted
    Keywords: GPS ; Geodynamics ; Mediterranean ; Vertical deformation ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.07. Tectonophysics::04.07.01. Continents ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
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  • 55
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    Deep structure and tectonics of the northern-central Apennines as seen by regional-scale tomography and 3-D located earthquakes (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In this study we present new high-resolution, regional-scale, Vp and Vp/Vs models of the northern-central Apennines along with accurate 3-D locations of a large set of local earthquakes. The main velocity anomalies are consistent with the surface geology in the shallow layers and present evidence for fluids stored within the basement at greater depths beneath the extensional belt. The Adria and Tyrrhenian mantle are defined by positive velocity anomalies below 30 km depth, while a low-Vp, high-Vp/Vs region in between indicates the existence of a hydrated wedge. The results yield new constraints on active processes in the Apennines and more generally envisage the evolution of a postcollisional belt. Velocity anomalies and earthquakes are consistent with a complex system of delamination and sinking of the Adria continental lithosphere, with the peeling of the crust identified by intermediate-depth seismicity. Change of seismicity and structural patterns along the belt indicates that this tectonic process is diachronous and that fluids, released by sunken lithosphere, are stored within the crust, conditioning the occurrence of seismicity and the onset of extension.
    Description: Published
    Description: 5391-5403
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Local earthquake tomography ; tectonic of Apennines ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
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  • 56
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    Eruptive processes leading to the most explosive lava fountain at Etna volcano: The 23 November 2013 episode (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The 23 November 2013 lava fountain at Etna volcano was the most explosive of the last 44 episodes that have occurred at Etna in 2011–2013. We infer the total magma volume erupted by thermal images analysis and show that it was characterized by a very high time-averaged-discharge-rate (TADR) of ~360m3 s 1, having erupted ~1.6 × 106m3 of dense-rock equivalent magma volume in just 45 min, which is more than 3 times the TADR observed during previous episodes. Two borehole dilatometers confirmed the eruption dynamics inferred from the thermal images. When compared to the other lava fountains, this episode can be considered as the explosive end-member. However, the erupted volume was still comparable to the other lava fountain events. We interpret that the 23 November explosive end-member event was caused by more primitive and gas-rich magma entering the system, as demonstrated by the exceptional height reached by the lava fountain.
    Description: Published
    Description: 4912–4919
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Etna eruption ; paroxysmal explosive eruption ; lava fountain ; strainmeters ; lava fountain volume ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 57
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    Progression of spontaneous in-plane shear faults from sub-Rayleigh to compressional wave rupture speeds (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigate numerically the passage of spontaneous, dynamic in-plane shear ruptures from initiation to their final rupture speed, using very fine grids. By carrying out more than 120 simulations, we identify two different mechanisms controlling supershear transition. For relatively weaker faults, the rupture speed always passes smoothly and continuously through the range of speeds between the Rayleigh and shear wave speeds (the formerly considered forbidden zone of rupture speeds). This, however, occurs in a very short time, before the ruptures reach the compressional wave speed. The very short time spent in this range of speeds may explain why a jump over these speeds was seen in some earlier numerical and experimental studies and confirms that this speed range is an unstable range, as predicted analytically for steady state, singular cracks. On the other hand, for relatively stronger faults, we find that a daughter rupture is initiated by the main (mother) rupture, ahead of it. The mother rupture continues to propagate at sub-Rayleigh speed and eventually merges with the daughter rupture, whose speed jumps over the Rayleigh to shear wave speed range. We find that this daughter rupture is essentially a “pseudorupture,” in that the two sides of the fault are already separated, but the rupture has negligible slip and slip velocity. After the mother rupture merges with it, the slip, the slip velocity, and the rupture speed become dominated by those of the mother rupture. The results are independent of grid sizes and of methods used to nucleate the initial rupture.
    Description: Published
    Description: 8331–8345
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: open
    Keywords: Seismic source ; Supershear ruptures ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
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  • 58
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    Paleomagnetic evidence for a post-Eocene 90° CCW rotation of internal Apennine units: A linkage with Corsica-Sardinia rotation? (2014)
    American Geophysical Union
    Details
    Publication Date: 2017-10-06
    Description: We report on an extensive paleomagnetic study (36 sites) of the Tuscan Nappe succession from the Northern Apennines Arc, aimed to reconstruct the tectonic evolution of the internal sector of this chain. We analyzed Eocene pelagic foreland ramp deposits (Scaglia Toscana Formation) and Oligocene–lower Miocene siliciclastic turbidites (Macigno and Falterona Formations). Paleomagnetic results show that the internal sector of the Northern Apennines underwent large counterclockwise (CCW) rotations with respect to the Adria-Africa foreland. A decrease in the rotation magnitude was observed from the southern to the northern sector of the arc (from 91 to 36°). This trend is opposite to that observed in the more external units of Northern Apennines and demonstrates that the oroclinal bending model, which has been proposed for the external units of the chain, is not appropriate to explain the evolution of the internal sector of the arc. On the basis of the observed paleomagnetic pattern, we propose a new tectonic model in which the Tuscan and Falterona-Cervarola units in the southern area were first rotated CCW along with the Corsica-Sardinia block during its lower Miocene rotational drifting and were later involved in the main phases of rotational emplacement and translation toward the outermost sector (Umbria domain), thus yielding the final curved shape of the Northern Apennines chain. Data from this study represent the first paleomagnetic evidence of the influence of the Corsica-Sardinia CCW rotation in the Apennines orogenic wedge deformation, in the general framework of the geodynamic evolution of the Central Mediterranean subduction system.
    Description: Published
    Description: 374-392
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: paleomagnetism, Apennines, Tuscany ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
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  • 59
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    Explosive expansion of a slowly-decompressed magma analog:evidence of delayed bubble nucleation (2014)
    American Geophysical Union
    Details
    Publication Date: 2019-12-05
    Description: While ascending in the plumbing system of volcanoes, magma undergoes decompression at rates spanning several orders of magnitude and set by a number of factors internal and external to the volcano. Slow decompression generally results in an effusive or mildly explosive expansion of the magma, but counterexamples of sudden switches from effusive to explosive eruptive behaviour have been documented at various volcanoes worldwide. The mechanisms involved in this behavior are currently debated, in particular regarding basaltic magmas. Here, we explore the interplay between decompression rate and vesiculation vigour by decompressing a magma analog obtained by dissolving pine resin into acetone in varying proportions. Our mixtures contain solid particles and upon decompression experience the nucleation of acetone bubbles. We find mixtures high in acetone, containing smaller and fewer solid particles, experience strong supersaturation and fragment for very slow decompressions, despite having low viscosity, while mixtures low in acetone, with more and larger solid particles degas efficiently. We interpret our results in terms of delayed bubble nucleation due to a lack of efficient nucleation sites. We discuss how a similar mechanism might induce violent, explosive expansion in volatile-rich and poorly crystalline low-silica magmas, by analogy to previous inferences for rhyolitic magmas.
    Description: Published
    Description: 3067-3084
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: embargoed_20150613
    Keywords: Magma fragmentation ; basaltic magma ; analog laboratory experiments ; slow decompression ; bubble nucleation ; explosive volcanic eruptions ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism
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  • 60
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    Comment on “The winter anomaly in the middlelatitude F region during the solar minimum period observed by the Constellation Observing System for Meteorology, Ionosphere, and Climate” by W. K. Lee, H. Kil, Y.-S. Kwak, Q. Wu, S. Cho, and J. U. Park (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: Seasonal or winter anomaly in the F2 layer has been known since the beginning of regular ionospheric observations [e.g., Berkner and Wells, 1938, and references therein], and one may be sure that such a fundamental feature of this phenomenon as its height extent has been analyzed. However, Lee et al. [2011] using radio occultation Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Ne(h) observations have decided to reconsider this problem starting from the very beginning without any analyses of previous investigations and comparisons to earlier obtained results as if ionospheric F2 layer physics has started with them. Besides, the authors have done some incorrect statements which contradict the present theory of the ionospheric F2 layer. They claim that “The topside plasma density is greater in the summer hemisphere than in the winter hemisphere; … the electron density below the F peak at middle latitudes is also greater during summer than during winter; Therefore, the seasonal anomalous behavior is a phenomenon only near the F-peak height in the Northern Hemisphere; The question is why the seasonal behavior of the ionosphere near the F-peak height is different from the behavior below and above the F peak. ….there was no explanation for the different seasonal behaviors of electron density in the lower F region and at F-peak height”. This is the main contents and results of the paper. Let us consider what was known about winter anomaly before the paper by Lee et al. [2011].
    Description: Published
    Description: 7972–7978
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Description: restricted
    Keywords: December anomaly, ionosphere ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
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  • 61
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    Multidisciplinary Approach Yields Insight into Mt. Etna 2001 Eruption (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: On July 17,2001, lava began pouring down the slopes of Mt. Etna in Sicily signaling the start of the volcano's first flank eruption in nearly 10 years. Etna typically experiences long periods of explosive and effusive activity at the summit, which lies 3350 m a.s.l., interspersed with shorter flank eruptions. During the latter, large volumes of lava can threaten local populations. The Catania Section of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) routinely monitors the volcano with an array of integrated multidisciplinary techniques. During the 2001 flank eruption, researchers obtained the deepest insight yet into the mechanisms that control this fascinating volcano. In particular, by studying ground deformation, seismicity, gravity changes, and geomagnetism, researchers were able to forecast 3 to 4 days in advance the intrusion of a new feeder dike in the upper part of the volcano and follow the propagation of dike emplacement and fissure opening, as well as estimate the volume of the intrusion. During the eruption, volcanology gas geochemistry and petrology were used to distinguish two different magmas erupting at the same time from both this new feeder dike and the summit feeding system, which has been active since January 2001. Effusion rate measurements and thermal mapping of the flow field provided insight into the maximum length the lava flow could reach from the lower vent, and researchers were able to follow the process of tube formation along this flow. The previous flank eruption on Etna occurred between 1991 and 1993, when 235 million of lava poured from within the Valle del Bove (VDB) and formed a lava flow field over 8.5 km long that threatened the town of Zafferana. Since then, eruptive activity at Etna has been restricted to the summit area. A progressive increase in the activity occurred between June 1998 and February 1999, with a succession of 21 paroxysmal episodes from the Southeast Cone (SEC). Then, on February 1999, a fire fountain episode from the SEC indicated the start of the 1999 summit eruption, which produced two lava flow fields. During 2000, there were 66 fire fountain events from the SEC accompanied by small lava flows. Lava flow emission started again from the north base of the SEC in January 2001, and on May 9,2001, small fire fountaining episodes were observed on the summit and northern flank of the SEC.This activity gradually increased in frequency and intensity before the 2001 flank eruption.
    Description: Published
    Description: 653-656
    Description: 3V. Dinamiche e scenari eruttivi
    Description: N/A or not JCR
    Description: restricted
    Keywords: Etna eruption ; volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 62
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    A method for foF2 short-term (1–24 h) forecast using both historical and real-time foF2 observations over European stations: EUROMAP model (2014)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: A method for foF2 short-term forecast over Europe has been developed and implemented in the EUROMAP model. The input-driving parameters are 3 h ap indices (converted to ap(τ)), effective ionospheric T index, and real-time foF2 observations. The method includes local (for each station) regression storm models to describe strong negative disturbances under ap(τ)〉30 and training models to describe foF2 variations under ap(τ) ≤ 30. The derived model was tested in two regimes: descriptive when observed 3 h ap indices were used and real forecast when predicted daily Ap were used instead of 3 h ap indices—. In the case of strong negative disturbances the EUROMAP model demonstrates on average the improvement over the lnternational Reference Ionosphere STORM-time correction model (IRI(STORM)) model: 40% in winter, 24% in summer, and 39% in equinox. The average improvement over climatology is 41% in winter, 59% in summer, and 55% in equinox. In the majority of cases this difference is statistically significant. In the case of strong positive disturbances, higher-latitude stations also manifest a significant difference between the twomodels but this difference is insignificant at lower latitude stations. The substitution of 3 h ap input indices for the predicted daily Ap ones decreases the foF2 prediction accuracy in the case of negative disturbances but practically has no effect with positive disturbances. In both cases the proposed method manifests better accuracy than the IRI(STORM) model provides. The obtained results show a real opportunity to provide foF2 forecast with the (1–24 h) lead time on the basis of predicted Ap indices
    Description: Published
    Description: 253-270
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Description: restricted
    Keywords: forecast ; 01. Atmosphere::01.02. Ionosphere::01.02.03. Forecasts
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  • 63
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    Effect of different seawater Mg2 + concentrations on calcification in two benthic foraminifers (2014)
    Elsevier
    In:  EPIC3Marine Micropaleontology, Elsevier, 113, pp. 56-64, ISSN: 0377-8398
    Details
    Publication Date: 2019-08-19
    Description: Magnesium, incorporated in foraminiferal calcite (Mg/CaCC), is used intensively to reconstruct past seawater temperatures but, in addition to temperature, the Mg/CaCC of foraminiferal tests also depends on the ratio of Mg and Ca in seawater (Mg/CaSW). The physiological mechanisms responsible for these proxy relationships are still unknown. This culture study investigates the impact of different seawater [Mg2 +] on calcification in two benthic foraminiferal species precipitating contrasting Mg/CaCC: Ammonia aomoriensis, producing low-Mg calcite and Amphistegina lessonii, producing intermediate-Mg calcite. Foraminiferal growth and test thickness were determined and, Mg/Ca was analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Results show that at present-day seawater Mg/CaSW of ~ 5, both species have highest growth rates, reflecting their adaptation to modern seawater element concentrations. Test thickness is not significantly affected by different Mg/CaSW. The relationship between Mg/CaSW and Mg/CaCC shows a distinct positive y-axis intercept, possibly reflecting at least two processes involved in foraminiferal biomineralization. The associated Mg partition (DMg) changes non-linearly with increasing Mg/CaSW, hence suggesting that the DMg is best described by an exponential function approaching an asymptote.
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    Modeling the spreading of glacial meltwater from the Amundsen and Bellingshausen Seas (2014)
    American Geophysical Union
    In:  EPIC3Geophysical Research Letters, American Geophysical Union, 41(22), pp. 7942-7949, ISSN: 00948276
    Details
    Publication Date: 2019-07-16
    Description: It has been suggested that an increased melting of continental ice in the Amundsen Sea (AS) and Bellingshausen Sea (BS) is a likely source of the observed freshening of Ross Sea (RS) water. To test this hypothesis, we simulate the spreading of glacial meltwater using the Finite Element Sea Ice/Ice Shelf/Ocean Model. Based on the spatial distribution of simulated passive tracers, most of the basal meltwater from AS ice shelves flows toward the RS with more than half of the melt originating from the Getz Ice Shelf. Further, the model results show that a slight increase of the basal mass loss can substantially intensify the transport of meltwater into the RS due to a strengthening of the melt-driven shelf circulation and the westward flowing coastal current. This supports the idea that the basal melting of AS and BS ice shelves is one of the main sources for the RS freshening.
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    Modeling organic iron-binding ligands in a three-dimensional biogeochemical ocean model (2014)
    Elsevier
    In:  EPIC3Marine Chemistry, Elsevier, ISSN: 0304-4203
    Details
    Publication Date: 2015-01-05
    Description: Most dissolved iron in the ocean is bound to organic molecules with strong conditional stability constants, known as ligands that are found at concentrations ranging from 0.2 to more than 10 nmol L− 1. In this work we report the first mechanistic description of ligand dynamics in two three-dimensional models of ocean biogeochemistry and circulation. The model for ligands is based on the concept that ligands are produced both from organic matter remineralization and phytoplankton processes, and that they are lost through bacterial and photochemical degradation, as well as aggregation and to some extent in the process of phytoplankton uptake of ligand-bound iron. A comparison with a compilation of in-situ measurements shows that the model is able to reproduce some large-scale features of the observations, such as a decrease in ligand concentrations along the conveyor belt circulation in the deep ocean, lower surface and subsurface values in the Southern Ocean, or higher values in the mesopelagic than in the abyssal ocean. Modeling ligands prognostically (as opposed to assuming a uniform ligand concentration) leads to a more nutrient-like profile of iron that is more in accordance with data. It however, also leads to higher surface concentrations of dissolved iron and negative excess ligand L⁎ in some ocean regions. This is probably an indication that with more realistic and higher ligand concentrations near the surface, as opposed to the traditionally chosen low uniform concentration, iron modelers will have to re-evaluate their assumption of low scavenging rates for iron. Given their sensitivity to environmental conditions, spatio-temporal variations in ligand concentrations have the potential to impact primary production via changes in iron limitation.
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    A Mid-Holocene Shift and Millennial-Scale Variations in North Pacific Intermediate Water Oxygenation and Upper Ocean Hydrography (2014)
    American Geophysical Union
    In:  EPIC3American Geophysical Union Fall Meeting, San Francisco, CA, USA, 2014-12-15-2014-12-19Washington, D. C., USA, American Geophysical Union
    Details
    Publication Date: 2015-01-05
    Description: The subarctic North Pacific and its marginal seas constitute a key area in which rapid environmental changes over the past decades have been observed in instrumental records, like sea ice decreases, or alterations of nutrient inventories and oxygenation of mid-depth water masses. However, knowledge about the past climatic and oceanographic variability beyond instrumental time series in the subarctic North Pacific and its marginal seas is limited. Few temporally and spatially well-resolved high-resolution and spatially well datasets exist, with spatial and temporal coverage being insufficient to gain a detailed picture of past variations. Our proxydata-based study focuses on a collection of sediment records from the Okhotsk Sea as major source area for well ventilated North Pacific Intermediate Water (NPIW) that cover the last ca. 12,000 years with high temporal and adequate spatial resolution. We decipher rapid changes in NPIW ventilation patterns on centennial to millennial time scales and show that the current ventilation of the mid-depth North Pacific has likely only been prevalent for the last 2 ka. We further provide evidence for a Mid-Holocene shift in mid-depth NPIW ventilation characteristics. Additionally, changes in North Atlantic Deep Water flow speed and patterns are reflected in our records of North Pacific mid-depth water mass dynamics, thus indicating a hemispheric-wide connection between the Atlantic and Pacific regions during the Holocene. Planktic oxygen isotope data suggest a high variability in the stratification of local surface water masses and the formation of sea ice, influencing the formation of new, well ventilated water masses near to our core sites. We compare the main Holocene baseline changes evidenced in our proxy reconstructions to Early Holocene and Pre-Industrial time slice results from the fully-coupled MPI-ESM (COSMOS) Earth System Model, with a focus on the Pacific Ocean to better understand NPIW and upper ocean dynamic changes.
    Repository Name: EPIC Alfred Wegener Institut
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    Evaluation of long chain 1,14-alkyl diols in marine sediments as indicators for upwelling and temperature (2014)
    Elsevier
    In:  EPIC3Organic Geochemistry, Elsevier, 76, pp. 39-47, ISSN: 0146-6380
    Details
    Publication Date: 2015-01-13
    Description: Long chain alkyl diols form a group of lipids occurring widely in marine environments. Recent studies have suggested several palaeoclimatological applications for proxies based on their distributions, but have also revealed uncertainty about their applicability. Here we evaluate the use of long chain 1,14-alkyl diol indices for reconstruction of temperature and upwelling conditions by comparing index values, obtained from a comprehensive set of marine surface sediments, with environmental factors such as sea surface temperature (SST), salinity and nutrient concentration. Previous studies of cultures indicated a strong effect of temperature on the degree of saturation and the chain length distribution of long chain 1,14-alkyl diols in Proboscia spp., quantified as the diol saturation index (DSI) and diol chain length index (DCI), respectively. However, values of these indices for surface sediments showed no relationship with annual mean SST of the overlying water. It remains unknown as to what determines the DSI, although our data suggest that it may be affected by diagenesis, while the relationship between temperature and DCI may be different for different Proboscia species. In addition, contributions from algae other than Proboscia diatoms may affect both indices, although our data provide no direct evidence for additional long chain 1,14-alkyl diol sources. Two other indices using the abundance of 1,14-diols vs. 1,13-diols and C30 1,15- diols have been applied previously as indicators for upwelling intensity at different locations. The geographical distribution of their values supports the use of 1,14 diols vs. 1,13 diols [C28 + C30 1,14-diols]/[(C28 + C30 1,13-diols) + (C28 + C30 1,14-diols)] as a general indicator for high nutrient or upwelling conditions.
    Repository Name: EPIC Alfred Wegener Institut
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    Cenozoic Arctic Ocean Climate History: Some highlights from the IODP Arctic Coring Expedition (ACEX) (2014)
    Elsevier
    In:  EPIC3Developments in Marine Geology, Elsevier, 7, pp. 259-293, ISSN: ISBN: 978-0-444-62617-2
    Details
    Publication Date: 2015-04-23
    Repository Name: EPIC Alfred Wegener Institut
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    Simulation and evaluation of 2-m temperature over Antarctica in polar regional climate model (2014)
    Springer
    In:  EPIC3Science China Earth Sciences, Springer, 57(4), pp. 703-709, ISSN: 1674-7313
    Details
    Publication Date: 2015-01-14
    Description: The European Centre for Medium-Range Weather Forecasts Reanalysis ERA40, National Centers for Environmental Prediction (NCEP) 20th-century reanalysis, and three station observations along an Antarctic traverse from Zhongshan to Dome-A stations are used to assess 2-m temperature simulation skill of a regional climate model. This model (HIRHAM) is from the Alfred Wegener Institute for Polar and Marine Research in Germany. Results show: (1) The simulated multiyear averaged 2-m temperature field pattern is close to that of ERA40 and NCEP; (2) the cold bias relative to ERA40 over all of Antarctic regions is 1.8°C, and that to NCEP reaches 5.1°C; (3) bias of HIRHAM relative to ERA40 has seasonal variation, with a cold bias mainly in the summer, as much as 3.4°C. There is a small inland warm bias in autumn of 0.3°C. Further analysis reveals that the reason for the cold bias of 2-m temperature is that physical conditions of the near-surface boundary layer simulated by HIRHAM are different from observations: (1) During the summer, observations show that near-surface atmospheric stability conditions have both inversions and non-inversions, which is due to the existence of both positive and negative sensible heat fluxes, but HIRHAM almost always simulates a situation of inversion and negative sensible heat flux; (2) during autumn and winter, observed near-surface stability is almost always that of inversions, consistent with HIRHAM simulations. This partially explains the small bias during autumn and winter.
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    Generation of unusual branched long chain alkanes from hydrous pyrolysis of anammox bacterial biomass (2014)
    Elsevier
    In:  EPIC3Organic Geochemistry, Elsevier, 76, pp. 136-145
    Details
    Publication Date: 2015-03-08
    Repository Name: EPIC Alfred Wegener Institut
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    Temperature trends during the Present and Last Interglacial periods – a multi-model-data comparison (2014)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 99, pp. 224-243, ISSN: 0277-3791
    Details
    Publication Date: 2015-12-14
    Description: Though primarily driven by insolation changes associated with well-known variations in Earth's astronomical parameters, the response of the climate system during interglacials includes a diversity of feedbacks involving the atmosphere, ocean, sea ice, vegetation and land ice. A thorough multi-model-data comparison is essential to assess the ability of climate models to resolve interglacial temperature trends and to help in understanding the recorded climatic signal and the underlying climate dynamics. We present the first multi-model-data comparison of transient millennial-scale temperature changes through two intervals of the Present Interglacial (PIG; 8–1.2 ka) and the Last Interglacial (LIG; 123–116.2 ka) periods. We include temperature trends simulated by 9 different climate models, alkenone-based temperature reconstructions from 117 globally distributed locations (about 45% of them within the LIG) and 12 ice-core-based temperature trends from Greenland and Antarctica (50% of them within the LIG). The definitions of these specific interglacial intervals enable a consistent inter-comparison of the two intervals because both are characterised by minor changes in atmospheric greenhouse gas concentrations and more importantly by insolation trends that show clear similarities. Our analysis shows that in general the reconstructed PIG and LIG Northern Hemisphere mid-to-high latitude cooling compares well with multi-model, mean-temperature trends for the warmest months and that these cooling trends reflect a linear response to the warmest-month insolation decrease over the interglacial intervals. The most notable exception is the strong LIG cooling trend reconstructed from Greenland ice cores that is not simulated by any of the models. A striking model-data mismatch is found for both the PIG and the LIG over large parts of the mid-to-high latitudes of the Southern Hemisphere where the data depicts negative temperature trends that are not in agreement with near zero trends in the simulations. In this area, the positive local summer insolation trend is counteracted in climate models by an enhancement of the Southern Ocean summer sea-ice cover and/or an increase in Southern Ocean upwelling. If the general picture emerging from reconstructions is realistic, then the model-data mismatch in mid and high Southern Hemisphere latitudes implies that none of the models is able to resolve the correct balance of these feedbacks, or, alternatively, that interglacial Southern Hemisphere temperature trends are driven by mechanisms which are not included in the transient simulations, such as changes in the Antarctic ice sheet or meltwater-induced changes in the overturning circulation.
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    Abrupt Climate Change Modeling (2014)
    Springer
    In:  EPIC3Encyclopedia of Complexity and Systems Science, Encyclopedia of Complexity and Systems Science, Springer, pp. 1-30
    Details
    Publication Date: 2015-03-10
    Repository Name: EPIC Alfred Wegener Institut
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    New aeromagnetic view of the geological fabric of southern Dronning Maud Land and Coats Land, East Antarctica (2014)
    Elsevier
    In:  EPIC3Gondwana Research, Elsevier, 25(1), pp. 358-367, ISSN: 1342-937X
    Details
    Publication Date: 2017-10-17
    Description: The ice shield of Antarctica, which measures several kilometers in thickness, presents a challenge when attempting to unravel the subglacial geology. Here, we report about systematic airborne magnetic surveys conducted over the last decade, which investigated a significant part of Dronning Maud Land (DML), imaging for the first time the crustal architecture of the interior of this sector of East Antarctica. High-resolution data reveal parallel, elongated magnetic anomalies in southeastern DML. These NW–SE trending anomalies can be traced farther east into sparser Russian magnetic data sets. Several high amplitude magnetic anomalies with values above 400 nT have been observed in southwesternDML and Coats Land. They differ clearly inwavelength and amplitudes fromthe magnetic pattern found in the east and do not show any evidence of a Pan-African orogenic belt or suture zone connecting the Shackleton Range with easternDML, as hypothesized in several studies. This leads to the assumption of the existence of a hitherto unrecognized large tectonic province in southeastern DML.Whereas an over 100 km long magnetic lineament in the interior of the DronningMaud Landmay reflect a major shear zone akin to the Pan-African age Heimefrontfjella shear zone. Both findings bring new evidences to the still open question about the amalgation of East and West Gondwana. In addition, the magnetic data allow mapping the eastern extent of the presumable cratonic province of Coats Land, a region considered as a key piercing point for reconstructions of Rodinia. Furthermore, the Beattie Magnetic Anomaly in southern Africa is assumed to continue into East Antarctica. Two magnetic highs in western DML are identified as possible eastward continuation of this prominent anomaly.
    Repository Name: EPIC Alfred Wegener Institut
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    Reconstruction of changes in the Weddell Sea sector of the Antarctic Ice Sheet since the Last Glacial Maximum (2014)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 100, pp. 111- 136, ISSN: 0277-3791
    Details
    Publication Date: 2018-08-10
    Description: Abstract The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica's continental ice volume. Over the last few decades, studies on glacial–geological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23–19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on the Weddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different ice-sheet models have reconstructed conflicting {LGM} ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the {LGM} sea-level low-stand of ~130 m vary considerably. In this paper, we summarise and review the geological records of past ice-sheet margins and past ice-sheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the {LGM} ice-sheet configuration, including time-slice reconstructions for post-LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacial–geological datasets on Antarctic Ice-Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical ice-sheet models.
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    Neoglacial change in deep water exchange and increase of sea-ice transport through eastern Fram Strait: evidence from radiogenic isotopes (2014)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 92, pp. 190-207, ISSN: 0277-3791
    Details
    Publication Date: 2014-06-02
    Description: Sediment core MSM5/5-712 from the West Spitsbergen continental margin has been investigated at high resolution for its seawater-derived neodymium (Nd) and lead (Pb) isotope compositions stored in ferromanganese oxyhydroxide coatings of the sediment particles to reconstruct Holocene changes in the sources and mixing of bottom waters passing the site. The radiogenic isotope data are used in combination with a multitude of proxy indicators for the climatic and oceanographic development of the eastern Fram Strait during the past 8500 years. To calibrate the downcore data, seawater and core top samples from the area were analysed for their radiogenic isotope compositions. Core top leachates reveal relatively high (more radiogenic) Nd isotope compositions between εNd −9.7 and −9.1, which are higher than present-day seawater εNd in eastern Fram Strait (−12.6 to −10.5) and indicate that the seawater values have only been established very recently. The core top data agree well with the downcore signatures within the uppermost 40 cm of the sediment core (εNd −9.1 to −8.8) indicating a reduced inflow of waters from the Nordic Seas, concurrent with cool conditions and a south-eastward shift of the marginal ice zone after ca 2.8 cal ka BP (Late Holocene). High sea-ice abundances in eastern Fram Strait are coeval with the well-known Neoglacial trend in the northern North Atlantic region. In contrast, warmer conditions of the late Early to Mid-Holocene were accompanied by lower (less radiogenic) εNd signatures of the bottom waters indicating an increased admixture from the Nordic Seas (−10.6 to −10.1). A shift to significantly more radiogenic εNd signatures of the detrital material also occurred at 3 cal ka BP and was accompanied by a marked increase in supply of fine-grained ice-rafted material (IRF) from the Arctic Ocean to the core site. The most likely source areas for this radiogenic material are the shallow Arctic shelves, in particular the Kara Sea shelf. The evolution of the Pb isotope compositions of past seawater was dominated by local signatures characterized by high 208, 207, 206Pb/204Pb values during the warm Early and Mid-Holocene periods related to enhanced chemical weathering on Svalbard and high glacial and riverine input derived from young granitic (more radiogenic) material to the West Spitsbergen margin. At 3 cal ka BP both detrital and seawater Pb isotope data changed towards more Kara Sea-like signatures.
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    The seaward limit of wave effects on coastal macrobenthos (2014)
    Springer
    In:  EPIC3Helgoland Marine Research, Springer, 68(1), pp. 1-16, ISSN: 1438-387X
    Details
    Publication Date: 2016-07-19
    Description: Exposed sandy coasts are predominantly physically controlled environments where benthic communities are structured by the independent response of species to the physical environment, with minimal biological interactions (swash exclusion hypothesis). This prevalence of physical control may be regarded as a typical property of exposed coastal areas. In an offshore direction, the importance of wave effects on the benthos will diminish until a depth is reached where they are no longer significant [wave exclusion hypothesis (WEH)]. This loss of a coastal property may be used to define an offshore depth limit of the coastal zone. We used a large set of benthos data from the SE North Sea to test whether an offshore limit of the coast can be clearly recognised despite strong small-scale variability and how this limit would vary seasonally and from year to year. In accordance with WEH, both species density and total abundance of macrobenthos were low in the surf zone, strongly increased with depth, and averaged over all sampling dates became relatively constant below 30 m depth. Seasonally, these gradients were weaker during summer recruitment than during autumn. Species richness, by contrast, showed no significant difference with depth. In single years, the depth of the turning point from increasing abundances to constant abundances varied between 20 and 31 m (equivalent to 40–80 km off the coastline) depending on wave height. We conclude that this zone can be derived from benthic community gradients.
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    A multibiomarker approach to the assessment of pollution impacts in two Baltic Sea coastal areas in Sweden using caged mussels (Mytilus trossulus) (2014)
    Elsevier
    In:  EPIC3Science of The Total Environment, Elsevier, 473-47, pp. 398-409, ISSN: 0048-9697
    Details
    Publication Date: 2019-07-17
    Description: Blue mussels (Mytilus trossulus) were transplanted in cages for three months in two Swedish coastal areas in the Bothnian Sea (northern Baltic Sea) to investigate the interactions between analysed environmental chemicals and biological responses. A wide array of biological parameters (biomarkers) including antioxidant and biotransformation activity, geno-, cyto- and neurotoxic effects, phagocytosis, bioenergetic status and heart rate were measured to detect the possible effects of contaminants. Integrated Biomarker Response index and Principal Component Analysis performed on the individual biological response data were able to discriminate between the two study areas as well as the contaminated sites from their respective local reference sites. The two contaminated sites outside the cities of Sundsvall (station S1) and Gävle (station G1) were characterised by different biomarker response patterns. Mussels at station S1 showed a low condition index, increased heart rate recovery time and phagocytosis activity coinciding with the highest tissue concentrations of some trace metals, polycyclic aromatic hydrocarbons and organotins. At station G1 the highest organochlorine pesticide concentration was recorded as well as elevations in glutathione S-transferase activity, thiamine content and low lysosomal membrane stability. Significant variability in the geno- and cytotoxic responses and bioenergetic status was also observed at the different caging stations. The results obtained suggest that different chemical mixtures present in the study areas cause variable biological response patterns in organisms.
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    Cephalopods in neuroscience: regulations, research and the 3Rs (2014)
    Springer
    In:  EPIC3Invertebrate Neuroscience, Springer, ISSN: 1354-2516
    Details
    Publication Date: 2019-07-17
    Description: Cephalopods have been utilised in neurosci- ence research for more than 100 years particularly because of their phenotypic plasticity, complex and centralised nervous system, tractability for studies of learning and cellular mechanisms of memory (e.g. long-term potentia- tion) and anatomical features facilitating physiological studies (e.g. squid giant axon and synapse). On 1 January 2013, research using any of the about 700 extant species of ‘‘live cephalopods’’ became regulated within the European Union by Directive 2010/63/EU on the ‘‘Protection of Animals used for Scientific Purposes’’, giving cephalopods the same EU legal protection as previously afforded only to vertebrates. The Directive has a number of implications, particularly for neuroscience research. These include: (1) projects will need justification, authorisation from local competent authorities, and be subject to review including a harm-benefit assessment and adherence to the 3Rs princi- ples (Replacement, Refinement and Reduction). (2) To support project evaluation and compliance with the new EU law, guidelines specific to cephalopods will need to be developed, covering capture, transport, handling, housing, care, maintenance, health monitoring, humane anaesthesia, analgesia and euthanasia. (3) Objective criteria need to be developed to identify signs of pain, suffering, distress and lasting harm particularly in the context of their induction by an experimental procedure. Despite diversity of views existing on some of these topics, this paper reviews the above topics and describes the approaches being taken by the cephalopod research community (represented by the authorship) to produce ‘‘guidelines’’ and the potential contribution of neuroscience research to cephalopod welfare.
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    A second-order accurate in time IMplicit–EXplicit (IMEX) integration scheme for sea ice dynamics (2014)
    Elsevier
    In:  EPIC3Journal of Computational Physics, Elsevier, 263, pp. 375-392, ISSN: 0021-9991
    Details
    Publication Date: 2019-07-17
    Description: Current sea ice models use numerical schemes based on a splitting in time between the momentum and continuity equations. Because the ice strength is explicit when solving the momentum equation, this can create unrealistic ice stress gradients when using a large time step. As a consequence, noise develops in the numerical solution and these models can even become numerically unstable at high resolution. To resolve this issue, we have implemented an iterated IMplicit–EXplicit (IMEX) time integration method. This IMEX method was developed in the framework of an already implemented Jacobian-free Newton–Krylov solver. The basic idea of this IMEX approach is to move the explicit calculation of the sea ice thickness and concentration inside the Newton loop such that these tracers evolve during the implicit integration. To obtain second-order accuracy in time, we have also modified the explicit time integration to a second-order Runge–Kutta approach and by introducing a second-order backward difference method for the implicit integration of the momentum equation. These modifications to the code are minor and straightforward. By comparing results with a reference solution obtained with a very small time step, it is shown that the approximate solution is second-order accurate in time. The new method permits to obtain the same accuracy as the splitting in time but by using a time step that is 10 times larger. Results show that the second-order scheme is more than five times more computationally efficient than the splitting in time approach for an equivalent level of error.
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    The influence of intrinsic and extrinsic factors on developmental parameters and their relationships in the marine isopod Idotea linearis (Crustacea) (2014)
    Springer
    In:  EPIC3Hydrobiologia, Springer, 732, pp. 197-212, ISSN: 0018-8158
    Details
    Publication Date: 2014-05-06
    Description: Developmental and reproductive parameters and their relationships were studied in the marine isopod Idotea linearis. We hypothesized that (1) the temporal patterns of molting and growth undergo complex and sex-specific changes with age as well as with the onset of sexual maturation, and that (2) sexual maturation (and dependent parameters) is controlled by the photoperiod. Both males and females were singly cultured in the laboratory at two alternative photoperiods (constant long and short days, respectively) from hatching until death. Males molted and grew throughout their life, showing a steady increase in stage duration and body size with each molt. Females, in contrast, showed much more complex modifications in molt chronology due to reproductive demands. There was some variability in the stage number, when females reached maturity. Reaching maturity early in the succession of molts was associated with smaller body size at maturity, smaller size of broods, but higher average number of broods per lifetime. Post-puberty molts in females occurred without further growth, and successive broods did not differ in size. The photoperiod strongly affected sexual maturation (and thus in turn molting and growth patterns) in females, while males remained completely unaffected by the photo regime.
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  • 81
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    Mass, Volume and Velocity of the Antarctic Ice Sheet: Present-Day Changes and Error Effects (2014)
    Springer
    In:  EPIC3Surveys in Geophysics, Springer, pp. 1-25, ISSN: 0169-3298
    Details
    Publication Date: 2019-07-17
    Description: This study examines present-day changes of the Antarctic ice sheet (AIS) by means of different data sets. We make use of monthly gravity field solutions acquired by the Gravity Recovery and Climate Experiment (GRACE) to study mass changes of the AIS for a 10-year period. In addition to "standard" solutions of release 05, solutions based on radial base functions were used. Both solutions reveal an increased mass loss in recent years. For a 6-year period surface-height changes were inferred from laser altimetry data provided by the Ice, Cloud, and land Elevation Satellite (ICESat). The basin-scale volume trends were converted into mass changes and were compared with the GRACE estimates for the same period. Focussing on the Thwaites Glacier, Landsat optical imagery was utilised to determine ice-flow velocities for a period of more than two decades. This data set was extended by means of high-resolution synthetic aperture radar (SAR) data from the TerraSAR-X mission, revealing an accelerated ice flow of all parts of the glacier. ICESat data over the Thwaites Glacier were complemented by digital elevation models inferred from TanDEM-X data. This extended data set exhibits an increased surface lowering in recent times. Passive microwave remote sensing data prove the long-term stability of the accumulation rates in a low accumulation zone in East Antarctica over several decades. Finally, we discuss the main error sources of present-day mass-balance estimates: the glacial isostatic adjustment effect for GRACE as well as the biases between laser operational periods and the volume-mass conversion for ICESat.
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  • 82
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    A laboratory study of ikaite (CaCO3·6H2O) precipitation as a function of pH, salinity, temperature and phosphate concentration (2014)
    Elsevier
    In:  EPIC3Marine Chemistry, Elsevier, 162, pp. 10-18, ISSN: 0304-4203
    Details
    Publication Date: 2014-07-30
    Description: Ikaite (CaCO3·6H2O) has only recently been discovered in sea ice, in a study that also provided first direct evidence of CaCO3 precipitation in sea ice. However, little is as yet known about the impact of physico-chemical processes on ikaite precipitation in sea ice. Our study focused on how the changes in pH, salinity, temperature and phosphate (PO4) concentration affect the precipitation of ikaite. Experiments were set up at pH from 8.5 to 10.0, salinities from 0 to 105 (in both artificial seawater (ASW) and NaCl medium), temperatures from 0 to −4 °C andPO4 concentrations from0 to 50 μmol kg−1. The results show that in ASW, calcium carbonate was precipitated as ikaite under all conditions. In the NaCl medium, the precipitates were ikaite in the presence of PO4 and vaterite in the absence of PO4. The onset time (τ) at which ikaite precipitation started, decreased nonlinearly with increasing pH. In ASW, τ increased with salinity. In the NaCl medium, τ first increased with salinity up to salinity 70 and subsequently decreased with a further increase in salinity; it was longer in ASW than in the NaCl medium under the same salinity. τ did not vary with temperature or PO4 concentration. These results indicate that ikaite is very probably the only phase of calcium carbonate formed in sea ice. PO4 is not, as previously postulated, crucial for ikaite formation in sea ice. The change in pH and salinity is the controlling factor for ikaite precipitation in sea ice. Within the ranges investigated in this study, temperature and PO4 concentration do not have a significant impact on ikaite precipitation.
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  • 83
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    Factors influencing particulate lipid production in the East Atlantic Ocean. (2014)
    Elsevier
    In:  EPIC3Deep-Sea Research I, Elsevier, 89, pp. 56-67, ISSN: 0967-0637
    Details
    Publication Date: 2014-05-21
    Description: Extensive analyses of particulate lipids and lipid classes were conducted to gain insight into lipid production and related factors along the biogeochemical provinces of the Eastern Atlantic Ocean. Data are supported by particulate organic carbon (POC), chlorophyll a (Chl a), phaeopigments, Chl a concentrations and carbon content of eukaryotic micro-, nano- and picophytoplankton, including cell abundances for the latter two and for cyanobacteria and prokaryotic heterotrophs. We focused on the productive ocean surface (2 m depth and deep Chl a maximum (DCM)). Samples from the deep ocean provided information about the relative reactivity and preservation potential of particular lipid classes. Surface and DCM particulate lipid concentrations (3.5–29.4 μg L−1) were higher than in samples from deep waters (3.2–9.3 μg L−1) where an increased contribution to the POC pool was observed. The highest lipid concentrations were measured in high latitude temperate waters and in the North Atlantic Tropical Gyral Province (13–25°N). Factors responsible for the enhanced lipid synthesis in the eastern Atlantic appeared to be phytoplankton size (micro, nano, pico) and the low nutrient status with microphytoplankton having the most expressed influence in the surface and eukaryotic nano- and picophytoplankton in the DCM layer. Higher lipid to Chl a ratios suggest enhanced lipid biosynthesis in the nutrient poorer regions. The various lipid classes pointed to possible mechanisms of phytoplankton adaptation to the nutritional conditions. Thus, it is likely that adaptation comprises the replacement of membrane phospholipids by non-phosphorus containing glycolipids under low phosphorus conditions. The qualitative and quantitative lipid compositions revealed that phospholipids were the most degradable lipids, and their occurrence decreased with increasing depth. In contrast, wax esters, possibly originating from zooplankton, survived downward transport probably due to the fast sinking rate of particles (fecal pellets). The important contribution of glycolipids in deep waters reflected their relatively stable nature and degradation resistance. A lipid-based proxy for the lipid degradative state (Lipolysis Index) suggests that many lipid classes were quite resistant to degradation even in the deep ocean.
    Repository Name: EPIC Alfred Wegener Institut
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  • 84
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    The scientific challenge of bridging the gap from the local to the earth system level: lessons from the study of mangroves and people in North Brazil (2014)
    Springer
    In:  EPIC3Regional Environmental Change, Springer, ISSN: 1436-3798
    Details
    Publication Date: 2016-10-07
    Description: This article aims to address the challenges of sustainable earth system governance from a multi-scale level perspective. The local to regional system level reviews findings from a social-ecological system (SES) approach of a mangrove ecosystem in North Brazil. Seven challenges (Glaser et al. 2010) that could provide relevant knowledge to society were identified. Their respective justification and recommendations are presented here. Further, these “challenges from the field” are linked and discussed with those challenges on earth system level elaborated by the International Council for Science in 2010. There it was stressed that sustainability problems are increasingly caused by drivers from multiple spatial and institutional levels in a single global human-nature system. The comparison between the global and local to regional challenges shows that most of these are reappearing disregarding the level of analysis, indicating that there is a universal core of global change problems. However, there are gaps are visible which hamper the effective connections across the different spatial levels. These gaps pertain to i.e. the subjects of knowledge generation and stakeholder inclusion. The final section elaborates on these recognized gaps and their science-policy dimensions. The article closes with the identification of a number of factors which currently impede global sustainability efforts: shortcomings in inter- and transdisciplinary research practice, lack of consistent structures for earth system governance and shortcomings in dealing with up-scaling challenges whilst remaining locally relevant. A blueprint for a globally focused but regionally informed social-ecological analysis framework remains to be worked out.
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  • 85
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    Liquid water in snow (2014)
    American Geophysical Union
    In:  EPIC3Workshop at the Institute for Snow and Avalanche Research, EOS, Davos, Switzerland, American Geophysical Union
    Details
    Publication Date: 2019-07-17
    Description: From 2-4 April 2014 about 50 researchers attended the workshop „Liquid water in snow – measurements techniques and modeling approaches“ that took place at the Institute for Snow and Avalanche Research (SLF) in Davos, Switzerland – the first one since 1982 in Innsbruck, Austria. This is the report thereof.
    Repository Name: EPIC Alfred Wegener Institut
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  • 86
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    An assessment of global and regional sea level for years 1993–2007 in a suite of interannual CORE-II simulations (2014)
    Elsevier
    In:  EPIC3Ocean Modelling, Elsevier, 78, pp. 35-89, ISSN: 1463-5003
    Details
    Publication Date: 2014-05-26
    Description: We provide an assessment of sea level simulated in a suite of global ocean-sea ice models using the interannual CORE atmospheric state to determine surface ocean boundary buoyancy and momentum fluxes. These CORE-II simulations are compared amongst themselves as well as to observation-based estimates. We focus on the final 15 years of the simulations (1993–2007), as this is a period where the CORE-II atmospheric state is well sampled, and it allows us to compare sea level related fields to both satellite and in situ analyses. The ensemble mean of the CORE-II simulations broadly agree with various global and regional observation-based analyses during this period, though with the global mean thermosteric sea level rise biased low relative to observation-based analyses. The simulations reveal a positive trend in dynamic sea level in the west Pacific and negative trend in the east, with this trend arising from wind shifts and regional changes in upper 700 m ocean heat content. The models also exhibit a thermosteric sea level rise in the subpolar North Atlantic associated with a transition around 1995/1996 of the North Atlantic Oscillation to its negative phase, and the advection of warm subtropical waters into the subpolar gyre. Sea level trends are predominantly associated with steric trends, with thermosteric effects generally far larger than halosteric effects, except in the Arctic and North Atlantic. There is a general anti-correlation between thermosteric and halosteric effects for much of the World Ocean, associated with density compensated changes.
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  • 87
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    Morphological and molecular characterization of three new Azadinium species (Amphidomataceae, Dinophyceae) from the Irminger Sea (2014)
    Elsevier
    In:  EPIC3Protist, Elsevier, 165(4), pp. 417-444, ISSN: 1434-4610
    Details
    Publication Date: 2014-06-11
    Description: Some species of planktonic Azadinium produce azaspiracids (AZAs), a group of lipophilic phycotoxins causing human poisoning after mussel consumption. We describe three new species from the North Atlantic, all of which shared the same Kofoidean plate pattern characteristic for Azadinium: Po, cp, X, 4´, 3a, 6´´, 6C, 5S, 6´´´, 2´´´´. Azadinium trinitatum sp. nov. was mainly characterized by the presence of an antapical spine and by the position of the ventral pore at the left distal end of the pore plate in a cavity of plate 1´. Azadinium cuneatum sp. nov. had a conspicuously formed first apical plate, which was asymmetrically elongated and tapered on its left lateral side with a ventral pore located at the tip of this elongated 1´ plate. Azadinium concinnum sp. nov. was of particular small size (〈 10 µm) and characterized by an anteriorly elongated anterior sulcal plate and by large and symmetric precingular plates. The ventral pore was located inside the apical pore plate on the cells’ right lateral side. Molecular phylogenetics as inferred from concatenated SSU, ITS, and LSU sequence data supported the distinctiveness of the three new species. None of the new species produced any known AZAs in measurable amounts.
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  • 88
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    When shape matters: strategies of different Antarctic ascidians morphotypes to deal with sedimentation (2014)
    Elsevier
    In:  EPIC3Marine Environmental Research, Elsevier, 99, pp. 179-187, ISSN: 0141-1136
    Details
    Publication Date: 2014-09-25
    Description: Climate change leads to increased melting of tidewater glaciers in theWestern Antarctic Peninsula region and sediment bearing glacial melt waters negatively affects filter feeding species as solitary ascidians. In previous work the erect-forms Molgula pedunculata and Cnemidocarpa verrucosa (Order Stolidobranchiata) appeared more sensitive than the flat form Ascidia challengeri (Order Phlebobranchiata). Sedimentation exposure is expected to induce up-regulation of anaerobic metabolism by obstructing the organs of gas exchange (environmental hypoxia) or causes enhanced squirting activity (functional hypoxia). In this study we evaluated the possible relationship between ascidian morphotype and their physiological response to sedimentation. Together with some behavioural observations, we analysed the response of anaerobic metabolic parameters (lactate formation and glycogen consumption) in different tissues of three Antarctic ascidians, exposed to high sediment concentrations (200 mgL�1). The results were compared to experimental hypoxia (10% pO2) and exercise (induced muscular contraction) effects, in order to discriminate the effect of sediment on each species and morpho-type (erect vs. flat forms). Our results suggest that the styled (erect) C. verrucosa increases muscular squirting activity in order to expulse excessive material, while the flat-form A. challengeri reacts more passively by down-regulating its aerobic metabolism under sediment exposure. Contrary, the erect ascidian M. pedunculata did not show any measurable response to the treatments, indicating that filtration and ingestion activities were not reduced or altered even under high sedimentation (low energetic material) which could be disadvantageous on the long-term and could explain why M. pedunculata densities decline in the study area.
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  • 89
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    Indications for algae-degrading benthic microbial communities in deep-sea sediments along the Antarctic Polar Front (2014)
    Elsevier
    In:  EPIC3Deep Sea Research Part II: Topical Studies in Oceanography, Elsevier, 108, pp. 6-16, ISSN: 0967-0645
    Details
    Publication Date: 2014-11-11
    Description: Phytoplankton blooms in surface waters of the oceans are known to influence the food web and impact microbial as well as zooplankton communities. Numerous studies have investigated the fate of phytoplankton-derived organic matter in surface waters and shelf sediments, however, little is known about the effect of sinking algal biomass on microbial communities in deep-sea sediments. Here, we analyzed sediments of four regions in the Southern Atlantic Ocean along the Antarctic Polar Front that had different exposures to phytoplankton bloom derived organic matter. We investigated the microbial communities in these sediments using high-throughput sequencing of 16S rRNA molecules to determine microorganisms that were active and catalyzed reporter deposition fluorescence in situ hybridization to infer their abundance and distribution. The sediments along the Antarctic Polar Front harbored microbial communities that were highly diverse and contained microbial clades that seem to preferably occur in regions of high primary productivity. We showed that organisms affiliated with the gammaproteobacterial clade NOR5/OM60, which is known from surface waters and coastal sediments, thrive in the deep-sea. Benthic deep-sea NOR5 were abundant, diverse, distinct from pelagic NOR5 and likely specialized on the degradation of phytoplankton-derived organic matter, occupying a similar niche as their pelagic relatives. Algal detritus seemed to not only fuel the benthic microbial communities of large areas in the deep-sea, but also to influence communities locally, as we found a peak in Flavobacteriaceae-related clades that also include degraders of algal biomass. The results strongly suggest that phytoplankton-derived organic matter was rapidly exported to the deep-sea, nourished distinct benthic microbial communities and seemed to be the main energy source for microbial life in the seafloor of vast abyssal regions along the Antarctic Polar Front.
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  • 90
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    Isolation, characterization and cross amplification of eleven novel microsatellite loci for the hydrozoan coral Millepora (2014)
    Springer
    In:  EPIC3Conservation Genetics Resources, Springer, ISSN: 1877-7252
    Details
    Publication Date: 2019-07-16
    Description: Milleporidae are of high ecological and economic importance, as, together with the scleractinian corals, they belong to the main reef builders of tropical coral reefs. Coral reefs face severe threats mainly due to anthropogenic disturbance. Understanding their population structure and dynamics is crucial for any conservation effort. Here we report the first microsatellite loci for the Milleporidae. Eleven polymorphic markers were developed for the hydrozoan corals Millepora dichotoma from the Great Barrier Reef (Australia) and tested for amplification in M. dichotoma from the Red Sea (Egypt), as well as for Millepora platyphylla from the Pacific Ocean (Moorea, French Polynesia). All loci were variable with 4–15 alleles per locus. Nine loci were transferable between geographic regions and species. These are the first microsatellites for hydrozoan corals. They will provide valuable tools for characterizing the population structure and genetic diversity of the group thereby benefitting coral reef conservation.
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  • 91
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    Uptake of Fluorescent Iron Oxide Nanoparticles by Oligodendroglial OLN-93 Cells (2014)
    Springer
    In:  EPIC3Neurochemical Research, Springer, 39(2), pp. 372-383, ISSN: 0364-3190
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 92
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    Water column structure and statistics of Denmark Strait Overflow Water cyclones (2014)
    Elsevier
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 84, pp. 110-126, ISSN: 0967-0637
    Details
    Publication Date: 2014-04-04
    Description: Data from seven moorings deployed across the East Greenland shelfbreak and slope 280 km downstream of Denmark Strait are used to investigate the characteristics and dynamics of Denmark Strait Overflow Water (DSOW) cyclones. On average, a cyclone passes the mooring array every other day near the 900 m isobath, dominating the variability of the boundary current system. There is considerable variation in both the frequency and location of the cyclones on the slope, but no apparent seasonality. Using the year-long data set from September 2007 to October 2008, we construct a composite DSOW cyclone that reveals the average scales of the features. The composite cyclone consists of a lens of dense overflow water on the bottom, up to 300 m thick, with cyclonic flow above the lens. The azimuthal flow is intensified in the middle and upper part of the water column and has the shape of a Gaussian eddy with a peak depth-mean speed of 0.22 m/s at a radius of 7.8 km. The lens is advected by the mean flow of 0.27 m/s and self propagates at 0.45 m/s, consistent with the topographic Rossby wave speed and the Nof speed. The total translation velocity along the East Greenland slope is 0.72 m/s. The self-propagation speed exceeds the cyclonic swirl speed, indicating that the azimuthal flow cannot kinematically trap fluid in the water column above the lens. This implies that the dense water anomaly and the cyclonic swirl velocity are dynamically linked, in line with previous theory. Satellite sea surface temperature (SST) data are investigated to study the surface expression of the cyclones. Disturbances to the SST field are found to propagate less quickly than the in-situ DSOW cyclones, raising the possibility that the propagation of the SST signatures is not directly associated with the cyclones.
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  • 93
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    Biosignatures in chimney structures and sediment from the Loki’s Castle low-temperature hydrothermal vent field at the Arctic Mid-Ocean Ridge (2014)
    Springer
    In:  EPIC3Extremophiles, Springer, 18(3), pp. 545-560, ISSN: 1431-0651
    Details
    Publication Date: 2014-05-12
    Description: We investigated microbial life preserved in a hydrothermally inactive silica–barite chimney in comparison with an active barite chimney and sediment from the Loki’s Castle low-temperature venting area at the Arctic Mid-Ocean Ridge (AMOR) using lipid biomarkers. Carbon and sulfur isotopes were used to constrain possible metabolic pathways. Multiple sulfur (δ34S, ∆33S) isotopes on barite over a cross section of the extinct chimney range between 21.1 and 22.5 ‰ in δ34S, and between 0.020 and 0.034 ‰ in Δ33S, indicating direct precipitation from seawater. Biomarker distributions within two discrete zones of this silica–barite chimney indicate a considerable difference in abundance and diversity of microorganisms from the chimney exterior to the interior. Lipids in the active and inactive chimney barite and sediment were dominated by a range of 13C-depleted unsaturated and branched fatty acids with δ13C values between −39.7 and −26.7 ‰, indicating the presence of sulfur-oxidizing and sulfate-reducing bacteria. The majority of lipids (99.5 %) in the extinct chimney interior that experienced high temperatures were of archaeal origin. Unusual glycerol monoalkyl glycerol tetraethers (GMGT) with 0–4 rings were the dominant compounds suggesting the presence of mainly (hyper-) thermophilic archaea. Isoprenoid hydrocarbons with δ13C values as low as −46 ‰ also indicated the presence of methanogens and possibly methanotrophs.
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  • 94
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    New tools for the reconstruction of Pleistocene Antarctic sea ice (2014)
    Elsevier
    In:  EPIC3Palaeogeography, Palaeoclimatology, Palaeoecology, Elsevier, 399, pp. 260-283, ISSN: 0031-0182
    Details
    Publication Date: 2014-05-06
    Description: Based on the quantitative analysis of diatom assemblages preserved in 274 surface sediment samples recovered in the Pacific, Atlantic and western Indian sectors of the Southern Ocean we have defined a new reference database for quantitative estimation of late-middle Pleistocene Antarctic sea ice fields using the transfer function technique. The Detrended Canonical Analysis (DCA) of the diatom data set points to a unimodal distribution of the diatom assemblages. Canonical Correspondence Analysis (CCA) indicates that not only winter sea ice (WSI) but also summer sea surface temperature (SSST) represent the most prominent environmental variables that control the spatial species distribution. To test the applicability of transfer functions for sea ice reconstruction in terms of concentration and occurrence probability we applied four different methods, the Imbrie and Kipp Method (IKM), the Modern Analog Technique (MAT), Weighted Averaging (WA), and Weighted Averaging Partial Least Squares (WAPLS), using logarithm-transformed diatom data and satellite-derived (1981-2010) sea ice data as a reference. The best performance for IKM results was obtained using a subset of 172 samples with 28 diatom taxa/taxa groups, quadratic regression and a three-factor model (IKM-D172/28/3q) resulting in root mean square errors of prediction (RMSEP) of 7.27% and 11.4% for WSI and summer sea ice (SSI) concentration, respectively. MAT estimates were calculated with different numbers of analogs (4, 6) using a 274-sample/28-taxa reference data set (MAT-D274/28/4an, -6an) resulting in RMSEP´s ranging from 5.52% (4an) to 5.91% (6an) for WSI as well as 8.93% (4an) to 9.05% (6an) for SSI. WA and WAPLS performed less well with the D274 data set, compared to MAT, achieving WSI concentration RMSEP´s of 9.91% with WA and 11.29% with WAPLS, recommending the use of IKM and MAT. The application of IKM and MAT to surface sediment data revealed strong relations to the satellite-derived winter and summer sea ice field. Sea ice reconstructions performed on an Atlantic- and a Pacific Southern Ocean sediment core, both documenting sea ice variability over the past 150,000 years (MIS 1 – MIS 6), resulted in similar glacial/interglacial trends of IKM and MAT-based sea-ice estimates. On the average, however, IKM estimates display smaller WSI and slightly higher SSI concentration and probability at lower variability in comparison with MAT. This pattern is a result of different estimation techniques with integration of WSI and SSI signals in one single factor assemblage by applying IKM and selecting specific single samples, thus keeping close to the original diatom database and included variability, by MAT. In contrast to the estimation of WSI, reconstructions of past SSI variability remains weaker. Combined with diatom-based estimates, the abundance and flux pattern of biogenic opal represents an additional indication for the WSI and SSI extent.
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  • 95
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    Spatial and seasonal population dynamics of sympatric Jassa species (Crustacea, Amphipoda) (2014)
    Elsevier
    In:  EPIC3Journal of Experimental Marine Biology and Ecology, Elsevier, 459, pp. 8-16, ISSN: 0022-0981
    Details
    Publication Date: 2014-06-02
    Description: Marine fouling communities are often characterised by dense aggregations of tube-building amphipod species of the genus Jassa. Although some species of this genus coexist in high densities, the development and relationships of sympatric populations are largely unknown. The current field study tested for the effects of exposure duration, seasonality and spatial heterogeneity on community composition, population structure and recruitment of three coexisting Jassa species. The establishment and succession of Jassa-dominated fouling communities on artificial substratum (PVC panels) were studied over two one-year periods off the island of Helgoland (German Bight, North Sea). At different seasonal times, and for different periods of time, panels were exposed at three stations: an exposed station (near water surface), a benthic station in 10 m water depth, and a sheltered station (near water surface). Jassa falcata was the dominant species at the benthic station in 10 m water depth, whereas Jassa marmorata and Jassa herdmani were more abundant on panels which were positioned near the water surface (exposed and sheltered station). The two latter species showed higher abundances at the exposed than at the sheltered station, although J. marmorata was always clearly the dominant species. The differences in the spatial distribution patterns of the three species may partly result from direct interspecific competition for space. Populations of all three Jassa species exhibited strong temporal changes in both abundances and population structure (sex ratio, proportions of reproductively active individuals, male morphs), most likely caused by seasonal factors. Rapid colonisation of free artificial surfaces was observed nearly throughout the year. Intensity of colonisation, however, followed a distinct seasonal pattern with a maximum in the summer months. Recruitment probably occurred via drifting juveniles which originated from amphipod communities in the surroundings. The observed differences among the species may mainly reflect adaptations to different environmental conditions. These differences, however, may also contribute to a stable long-term coexistence via some degree of resource partitioning along with ‘intermediate disturbance’ events.
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  • 96
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    The Opening of the Arctic-Atlantic Gateway: Tectonic, Oceanographic and Climatic Dynamics - an IODP Initiative (2014)
    American Geophysical Union
    In:  EPIC3AGU Fall Meeting, San Francisco, 2014-12-15-2014-12-19American Geophysical Union
    Details
    Publication Date: 2014-08-03
    Description: The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with stepwise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The opening of the Drake Passage finalized the oceanographic isolation of Antarctica, some 40 Ma ago. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth’s past and modern climate, little is known about its Cenozoic development. However, the opening history and AAG’s consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic Ocean and the North Atlantic. To study the AAG’s complete history, ocean drilling at two primary sites and one alternate site located between 73°N and 78°N are proposed. These sites will provide unprecedented sedimentary records that will unveil (1) the history of shallow-water exchange between the Arctic Ocean and the North Atlantic, and (2) the development of the AAG to a deep-water connection and its influence on the global climate system. The specific overarching goals of our proposal are to study: • the influence of distinct tectonic events in the development of the AAG and the formation of deep water passage on the North Atlantic and Arctic paleoceanography, and • the role of the AAG in the climate transition from the Paleogene greenhouse to the Neogene icehouse for the long-term (~50 Ma) climate history of the northern North Atlantic.
    Repository Name: EPIC Alfred Wegener Institut
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  • 97
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    Predictive habitat modelling of humpback (Megaptera novaeangliae) and Antarctic minke (Balaenoptera bonaerensis) whales in the Southern Ocean as a planning tool for seismic surveys (2014)
    Elsevier
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 91, pp. 101-114, ISSN: 0967-0637
    Details
    Publication Date: 2014-08-18
    Description: Seismic surveys are frequently a matter of concern regarding their potentially negative impacts on marine mammals. In the Southern Ocean, which provides a critical habitat for several endangered cetacean species, seismic research activities are undertaken at a circumpolar scale. In order to minimize impacts of these surveys, pre-cruise planning requires detailed, spatio-temporally resolved knowledge on the likelihood of encountering these species in the survey area. In this publication we present predictive habitat modelling as a potential tool to support decisions for survey planning. We associated opportunistic sightings (2005–2011) of humpback (Megaptera novaeangliae, N=93) and Antarctic minke whales (Balaenoptera bonaerensis, N=139) with a range of static and dynamic environmental variables. A maximum entropy algorithm (Maxent) was used to develop habitat models and to calculate daily basinwide/circumpolar prediction maps to evaluate how species-specific habitat conditions evolved throughout the spring and summer months. For both species, prediction maps revealed considerable changes in habitat suitability throughout the season. Suitable humpback whale habitat occurred predominantly in ice-free areas, expanding southwards with the retreating sea ice edge, whereas suitable Antarctic minke whale habitat was consistently predicted within sea ice covered areas. Daily, large-scale prediction maps provide a valuable tool to design layout and timing of seismic surveys as they allow the identification and consideration of potential spatio-temporal hotspots to minimize potential impacts of seismic surveys on Antarctic cetacean species.
    Repository Name: EPIC Alfred Wegener Institut
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  • 98
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    New constraints on the timing of West Antarctic Ice Sheet retreat in the eastern Amundsen Sea since the Last Glacial Maximum (2014)
    Elsevier
    In:  EPIC3Global and Planetary Change, Elsevier, 122, pp. 224-237, ISSN: 0921-8181
    Details
    Publication Date: 2018-08-10
    Description: Glaciers flowing into the Amundsen Sea Embayment (ASE) account for 〉35% of the total discharge of the West Antarctic Ice Sheet (WAIS) and have thinned and retreated dramatically over the past two decades. Here we present detailed marine geological data and an extensive new radiocarbon dataset from the eastern ASE in order to constrain the retreat of the WAIS since the Last Glacial Maximum (LGM) and assess the significance of these recent changes. Our dating approach, relying mainly on the acid insoluble organic (AIO) fraction, utilises multi-proxy analyses of the sediments to characterise their lithofacies and determine the horizon in each core that would yield the most reliable age for deglaciation. In total, we dated 69 samples and show that deglaciation of the outer shelf was underway before 20,600 calibrated years before present (cal. yr BP), reaching the mid-shelf by 13,575 cal. yr BP and the inner shelf to within c.150 km of the present grounding line by 10,615 cal. yr BP. The timing of retreat is broadly consistent with previously published radiocarbon dates on biogenic carbonate from the eastern ASE as well as AIO 14C ages from the western ASE and provides new constraints for ice sheet models. The overall retreat trajectory – slow on the outer shelf, more rapid from the middle to inner shelf – clearly highlights the importance of reverse bedslopes in controlling phases of accelerated groundling line retreat. Despite revealing these broad scale trends, the current dataset does not capture detailed changes in ice flow, such as stillstands during grounding line retreat (i.e., deposition of grounding zone wedges) and possible readvances as depicted in the geomorphological record.
    Repository Name: EPIC Alfred Wegener Institut
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  • 99
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    Isolation and characterization of 11 microsatellite markers from the squat lobster Munida gregaria (Decapoda: Galatheidae) around the Falkland Islands/Islas Malvinas (2014)
    Springer
    In:  EPIC3Conservation Genetics Resources, Springer, ISSN: 1877-7252
    Details
    Publication Date: 2014-09-04
    Description: Understanding phylogenetic relationship and patterns of contemporary population genetic structure is a prerequisite for conservation and management of potential fishery resources. In this study we report the isolation and characterization of 11 polymorphic microsatellite loci for the squat lobster Munida gregaria from around the Falkland Islands/Islas Malvinas. The number of alleles ranged from 3 to 31, observed heterozygosity varied from 0.130 to 0.870. Cross-amplification was 100 % successfully in the species/morph M. subrugosa and 36.4 % in another congeneric species M. gracilis. This set of microsatellites is useful for studies focused on taxonomy, genetic diversity and genetic connectivity further may provide stock assessment information for monitoring this important fishery resource.
    Repository Name: EPIC Alfred Wegener Institut
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  • 100
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    A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum (2014)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 100, pp. 1-9, ISSN: 0277-3791
    Details
    Publication Date: 2018-08-10
    Description: The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica’s continental ice volume. Over the last few decades, studies on glacialegeological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23e19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on theWeddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different icesheet models have reconstructed conflicting LGM ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the LGM sealevel low-stand of w130 m vary considerably. In this paper, we summarise and review the geological records of past ice-sheet margins and past icesheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the LGM ice-sheet configuration, including time-slice reconstructions for post- LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacialegeological datasets on Antarctic Ice- Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical icesheet models
    Repository Name: EPIC Alfred Wegener Institut
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