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  • Springer  (379,319)
  • American Chemical Society  (185,282)
  • Institute of Physics  (130,932)
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  • Public Library of Science  (79,304)
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  • 2015-2019  (755,996)
  • 1970-1974  (146,179)
  • 1945-1949  (15,560)
  • 1930-1934
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  • 101
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    Influence of snow depth and surface flooding on light transmission through Antarctic pack ice (2017)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 122(3), pp. 2108-2119, ISSN: 0148-0227
    Details
    Publication Date: 2017-04-26
    Description: Snow on sea ice alters the properties of the underlying ice cover as well as associated physical and biological processes at the interfaces between atmosphere, sea ice, and ocean. The Antarctic snow cover persists during most of the year and contributes significantly to the sea-ice mass due to the widespread surface flooding and related snow-ice formation. Snow also enhances the sea-ice surface reflectivity of incoming shortwave radiation and determines therefore the amount of light being reflected, absorbed, and transmitted to the upper ocean. Here, we present results of a case study of spectral solar radiation measurements under Antarctic pack ice with an instrumented Remotely Operated Vehicle in the Weddell Sea in 2013. In order to identify the key variables controlling the spatial distribution of the under-ice light regime, we exploit under-ice optical measurements in combination with simultaneous characterization of surface properties, such as sea-ice thickness and snow depth. Our results reveal that the distribution of flooded and nonflooded sea-ice areas dominates the spatial scales of under-ice light variability for areas smaller than 100 m-by-100 m. However, the heterogeneous and highly metamorphous snow on Antarctic pack ice obscures a direct correlation between the under-ice light field and snow depth. Compared to the Arctic, light levels under Antarctic pack ice are extremely low during spring (〈0.1%). This is mostly a result of the distinctly different dominant sea ice and snow properties with seasonal snow cover (including strong surface melt and summer melt ponds) in the Arctic and a year-round snow cover and widespread surface flooding in the Southern Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 102
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    Fram Strait and Greenland Sea transports, water masses, and water mass transformations 1999-2010 (and beyond) (2016)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 121(4), pp. 2314-2346, ISSN: 0148-0227
    Details
    Publication Date: 2017-06-15
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 103
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    Fishing for scavengers: an integrated study to amphipod (Crustacea: Lysianassoidea) diversity of Potter Cove (South Shetland Islands, Antarctica) (2017)
    Springer
    In:  EPIC3Marine Biodiversity, Springer, pp. 1-24, ISSN: 1867-1616
    Details
    Publication Date: 2017-06-23
    Description: Amphipoda from the superfamily Lysianassoidea Dana, 1849 play an important role in Southern Ocean benthic food webs due to their high biomass, abundance and predominantly scavenging mode of feeding. Our knowledge on the lysianassoid fauna, even in well-studied areas of the Western Antarctic Peninsula, is incomplete. Here we report the findings of an integrated study of lysianassoid amphipods of Potter Cove, King George Island/Isla 25 de Mayo (KGI), combining morphological and molecular species identification (COI barcoding) methods, investigating more than 41,000 specimens from baited traps. For comparison, 2,039 specimens from the adjacent Marian Cove were analysed. Ten lysianassoid species were recorded in the deeper outer Potter Cove, whereas the inner cove (〈50 m) was dominated by a single species, Cheirimedon femoratus Pfeffer, 1888 (99.44% relative abundance). It is hypothesised that the impoverished lysianassoid fauna inside the meltwater-influenced inner cove represents a model for future conditions along the Western Antarctic Peninsula under conditions of increased glacial melting. Abyssorchomene charcoti (Chevreux, 1912) and Orchomenella pinguides Walker, 1903 were recorded in KGI waters for the first time. Furthermore, one new lysianassoid amphipod species of the genus Orchomenella Sars, 1890 is described: Orchomenella infinita sp. n. Seefeldt, 2017. First-time DNA barcode data was established for Cheirimedon femoratus, Hippomedon kergueleni Miers, 1875, Orchomenella rotundifrons K.H. Barnard, 1932 and Orchomenella infinita sp. n.
    Repository Name: EPIC Alfred Wegener Institut
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  • 104
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    Snow thickness profiling on Antarctic sea-ice with GPR – rapid and accurate measurements with the potential to upscale needles to a haystack (2017)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2021-01-26
    Description: Snow thickness on sea ice is a largely under-sampled parameter, yet of importance for the sea-ice mass balance and for satellite based sea-ice thickness estimates and thus our general understanding of global ice-volume change. Traditional direct thickness measurements with meter sticks can provide accurate but only spot information, referred to as "needles" due to their pinpoint focus and information while airborne and satellite remote sensing snow products, referred to as "the haystack" have large uncertainties due to their scale. We demonstrate the remarkable accuracy and applicability of ground penetrating radar (GPR) snow-thickness measurements by comparing them with in-situ, meter-stick data from two field campaigns to Antarctica in late winter/early spring. The efficiency and millimeter- to centimeter accuracy of GPR enables practitioners to acquire extensive, semi-regional data with the potential to upscale "needles" to "the haystack" and to potentially calibrate satellite remote sensing products that we confirm to derive roughly 30 % of the in-situ thickness. We find the radar wave propagation velocity in snow to be rather constant (+/- 6%), encouraging regional snow-thickness surveys. Snow thinner than 10 cm is under the detection limit with the off-the-shelf GPR setup utilized in our study.
    Repository Name: EPIC Alfred Wegener Institut
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  • 105
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    Seasonal cycle of hydrography on the eastern shelf of the Filchner Trough, Weddell Sea, Antarctica (2017)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 122(8), pp. 6437-6453, ISSN: 0148-0227
    Details
    Publication Date: 2019-10-04
    Description: New two-year long records from three moorings, located at 76°S along the eastern flank and shelf of the Filchner Trough, give insight in the seasonal cycle of hydrography to a region where Modified Warm Deep Water (MWDW) enters the southern Weddell Sea continental shelf, possibly reaching the Filchner Ronne Ice Shelf, the biggest ice shelf (by volume) in Antarctica. A persistent northward flow of Ice Shelf Water (ISW) is found along the slope of the trough at 600 m depth, while the data on the shelf indicate a seasonal cycle, characterized by four phases. A distinct warm inflow period (separated in two phases), with maximum temperatures of −1°C, appears to be related to the seasonal heaving of the Antarctic Slope Front thermocline along the continental shelf break further north and a seasonal extension of the ISW layer onto the Eastern Shelf. The density gradients between the ISW in the trough and the MWDW on the adjacent shelf drive the southward flow during these phases. A flow reversal is found in winter, ceasing the southward flow along the eastern flank of the trough. Weaker density gradients between the trough and the shelf during winter allow a westward flow, partly driven by a N-S density gradient, existing across the Eastern Shelf during this time. From spring through to summer the ISW layer in the trough extends onto the eastern shelf where it occupies the bottom layer at our moorings and it is associated with northward flow.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 106
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    Effects of prolonged darkness and temperature on the lipid metabolism in the benthic diatom Navicula perminuta from the Arctic Adventfjorden, Svalbard (2017)
    Springer
    In:  EPIC3Polar Biology, Springer, 40(7), pp. 1425-1439, ISSN: 0722-4060
    Details
    Publication Date: 2017-08-10
    Description: The Arctic represents an extreme habitat for phototrophic algae due to long periods of darkness caused by the polar night (~4 months darkness). Benthic diatoms, which dominate microphytobenthic communities in shallow water regions, can survive this dark period, but the underlying physiological and biochemical mechanisms are not well understood. One of the potential mechanisms for long-term dark survival is the utilisation of stored energy products in combination with a reduced basic metabolism. In recent years, water temperatures in the Arctic increased due to an ongoing global warming. Higher temperatures could enhance the cellular energy requirements for the maintenance metabolism during darkness and, therefore, accelerate the consumption of lipid reserves. In this study, we investigated the macromolecular ratios and the lipid content and composition of Navicula cf. perminuta Grunow, an Arctic benthic diatom isolated from the microphytobenthos of Adventfjorden (Svalbard, Norway), over a dark period of 8 weeks at two different temperatures (0 and 7 °C). The results demonstrate that N. perminuta uses the stored lipid compound triacylglycerol (TAG) during prolonged dark periods, but also the pool of free fatty acids (FFA). Under the enhanced temperature of 7 °C, the lipid resources were used significantly faster than at 0 °C, which could consequently lead to a depletion of this energy reserves before the end of the polar night. On the other hand, the membrane building phospho- and glycolipids remained unchanged during the 8 weeks darkness, indicating still intact thylakoid membranes. These results explain the shorter survival times of polar diatoms with increasing water temperatures during prolonged dark periods.
    Repository Name: EPIC Alfred Wegener Institut
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  • 107
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    Directional resonance variations across the Pernicana Fault, Mt Etna, in relation to brittle deformation fields (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The Pernicana Fault (PF) is the main structural element of Mt Etna and the northern boundary of a section sliding to the southeast. Observed ground motion records in the damage zone of the PF show strong variations of directional resonance in the horizontal plane. The observed resonance directions exhibit an abrupt rotation of azimuth by about 30◦ across the fault, varying from N166◦ on the north side to N139◦ on the south. We interpret the directional resonance observations in terms of changes in the kinematics and deformation fields on the opposite sides of the fault. The northern side is affected primarily by the left-lateral strike-slip movement, whereas the southern side, that is subjected also to sliding, is under a dominant extensional stress regime. Brittle deformation models based on the observed kinematic field predict different sets of fractures on the opposite sides of the fault: synthetic cleavages and extensional fractures are expected to dominate in the northern and southern sides, respectively. These two fracture fields have different orientations (N74◦ and N42◦, respectively) and both show a near-orthogonal relation (∼88◦ in the northern sector and ∼83◦ to the south) with the azimuth of the observed directional resonance. We conclude that the direction of the largest resonance motions is sensitive to and has transversal relationship with the dominant fracture orientation. The directional amplification is inferred to be produced by stiffness anisotropy of the fault damage zone, with larger seismic motions normal to the fractures.
    Description: Published
    Description: 986–996
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions; Site effects; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 108
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    Probabilistic short-term volcanic hazard in phases of unrest: A case study for tephra fallout (2015)
    Wiley
    Details
    Publication Date: 2017-04-04
    Description: During volcanic crises, volcanologists estimate the impact of possible imminent eruptions usually through deterministic modeling of the effects of one or a few preestablished scenarios. Despite such an approach may bring an important information to the decision makers, the sole use of deterministic scenarios does not allow scientists to properly take into consideration all uncertainties, and it cannot be used to assess quantitatively the risk because the latter unavoidably requires a probabilistic approach. We present a model based on the concept of Bayesian event tree (hereinafter named BET_VH_ST, standing for Bayesian event tree for short-term volcanic hazard), for short-term near-real-time probabilistic volcanic hazard analysis formulated for any potential hazardous phenomenon accompanying an eruption. The specific goal of BET_VH_ST is to produce a quantitative assessment of the probability of exceedance of any potential level of intensity for a given volcanic hazard due to eruptions within restricted time windows (hours to days) in any area surrounding the volcano, accounting for all natural and epistemic uncertainties. BET_VH_ST properly assesses the conditional probability at each level of the event tree accounting for any relevant information derived from the monitoring system, theoretical models, and the past history of the volcano, propagating any relevant epistemic uncertainty underlying these assessments. As an application example of the model, we apply BET_VH_ST to assess short-term volcanic hazard related to tephra loading during Major Emergency Simulation Exercise, a major exercise at Mount Vesuvius that took place from 19 to 23 October 2006, consisting in a blind simulation of Vesuvius reactivation, from the early warning phase up to the final eruption, including the evacuation of a sample of about 2000 people from the area at risk. The results show that BET_VH_ST is able to produce short-term forecasts of the impact of tephra fall during a rapidly evolving crisis, accurately accounting for and propagating all uncertainties and enabling rational decision making under uncertainty.
    Description: Published
    Description: 8805–8826
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: embargoed_20161231
    Keywords: short-term probabilistic volcanic hazard analysis ; bayesian event tree ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 109
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    Assessing annual global M6+ seismicity forecasts (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We consider a seismicity forecast experiment conducted during the last 4 yr. At the beginning of each year, three models make a 1-yr forecast of the distribution of large earthquakes everywhere on the Earth. The forecasts are generated and the observations are collected in the Collaboratory for the Study of Earthquake Predictability (CSEP). We apply CSEP likelihood measures of consistency and comparison to see how well the forecasts match the observations, and we compare results from some intuitive reference models. These results illustrate some undesirable properties of the consistency tests: the tests can be extremely sensitive to only a few earthquakes, and yet insensitive to seemingly obvious flaws—a na ̈ıve hypothesis that large earthquakes are equally likely everywhere is not always rejected. The results also suggest that one should check the assumptions of the so-called T and W comparison tests, and we illustrate some methods to do so. As an extension of model assessment, we explore strategies to combine forecasts, and we discuss the implications for operational earthquake forecasting. Finally, we make suggestions for the next generation of global seismicity forecast experiments.
    Description: Published
    Description: 422-431
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: probabilistic forecasting ; statistical seismology ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
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  • 110
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    The hydrological signature of a seismogenic source: coseismic hydrological changes in response to the 1915 Fucino (Central Italy) earthquake (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The M ∼ 7 1915 Fucino (Central Italy) earthquake represents one of the most destructive seismic events ever occurred in the Italian Peninsula. Several seismogenic faults have been proposed in the past decades as the source of the earthquake by means of different approaches and techniques that lead to a variety of speculations about the source mechanism and the fault location, often contrasting with one another. The 1915 earthquake produced a remarkable data set of 73 coseismic hydrological changes in the near and intermediate field that consist in variation of the flow of streams and springs, liquefaction, rise of water temperature and turbidity. In this paper, we study the coseismic water level changes induced by the 1915 earthquake in the near field to provide convincing clues on the geometry of the earthquake causative fault. We model the coseismic strain field induced by seventeen individual faults proposed through different approaches, and compare its pattern with the distribution of streamflow changes. We find: (i) clues on the most probable geometry of the earthquake causative fault. Best fits between modelled deformation and observed data are displayed by sources (derived by geological or seismological data) that share several distinctive features, as they are ∼135◦-striking, SW-dipping, 25–30-km-long normal faults located along the eastern side of the Fucino basin. These data point to the Serrone Fault and the Parasano Fault as the most likely causative structures and support the hypothesis that the coseismic ruptures observed in the field represented primary surface faulting. On the contrary, our calculations show that the Pescina Fault and the Ventrino Fault are secondary faults from the perspective of the hydrological response. Finally, one of the best scoring potential sources (from geological data) is a multifaulting system that considers the presence, in the central-western part of the basin, of fault splays synthetic and antithetic to the main seismogenic structures; therefore, we infer for these splays a possible active involvement in a 1915-like seismogenic process; (ii) evidence against a number of seismogenic structures that were previously associated with the earthquake. In particular, the plots of coseismic strain induced by sources uniquely derived by macroseismic or geodetic data prove to be inconsistent with the polarities of the hydrological signatures. Also, sources mainly characterized by reverse faulting and/or by right-lateral strike-slip component are discarded and (iii) as a final remark, we maintain that the study of the hydrological signatures of earthquake strain can offer an alternative tool in the investigation of the historical seismicity, to estimate the focal mechanism of major earthquakes capable of giving rise to a consistent data set of hydrological data.
    Description: Published
    Description: 1374-1388
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: 1915 Fucino earthquake ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 111
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    Laboratory activities for seismic and volcanic hazards education: a challenge for scientists (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Balanced information and education are fundamental prerequisites for risk prevention and preparedness. Among others, children embody our best chance to implant appropriate behaviors that will be recalled during hazardous situations and to involve adults according to a knowledge chain reaction. In this work, scientists challenge their communication skills to built a set of hands-on and learn-by-play based laboratory activities, for primary and secondary schools, addressing three major issues: (1) the location of earthquakes and volcanoes on Earth; (2) earthquakes and eruptions mechanisms; (3) earthquakes unpredictability. Students are asked to place volcanoes and earthquakes epicenters (issue 1) on a wooden plate puzzle according to Plate dynamics. To addresses eruption mechanisms (issue 2) and related hazard, we use backing soda forced blowing out from a volcano vent and suggest that a pyroclastic flow is fast, it can spread over a large area and raise high up to the stratosphere. Earthquake mechanisms (issue 2) are discussed describing the energy buildup, release, and transfer, using a wooden sticks bendand- break analogy. The display of acoustic waves caused by the breakage in different situations allows understanding of both the rupture energy and the wave attenuation. Earthquakes occurrence (issue 3) is addressed using steadily pulled blocks sliding on a frictional surface, where pins simulate asperities. These activities were tested, involving thousands of students. Discussions with students and teachers and the analysis of the answers to specific questionnaires gave us confidence that we proposed proper tools to raise risk awareness
    Description: Published
    Description: 89-93
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: restricted
    Keywords: Seismic and volcanic hazards, Outreach, Education ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 112
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    Cloudy with a Chance of ideas! ( Piovono idee!): an interactive learning experience on hydrogeological risk and climate change (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: On October 25th 2011 a devastating flood hit the Vara and Magra valleys in Italy and left an unforgettable scratch in the inhabitants’ minds. Cloudy with a Chance of ideas! (Piovono idee!) is an active journey of discovery and training on hydrogeological risk and climate change. Land preservation and safety of people living on it are issues, which we would like to help citizens get perception about, in order to instill awareness on the actions that can be taken towards risk mitigation. Cloudy with a Chance of ideas! stemmed from this belief, and it is the result of a collaborative planning in which primary and secondary school students, living within cities heavily hit by the flood, took actively part. Children were helped by experts and scientists to build an exhibition devoted to hydrogeological risk. Here interactive workspaces, games and educational laboratories, allow visitors explore concepts, phenomena and their consequences on land and inhabitants. Issues are addressed from a daily actions perspective, where everybody might make the difference towards sustainability and trigger good practices on natural hazards risk reduction.
    Description: Published
    Description: 121-124
    Description: 4A. Clima e Oceani
    Description: restricted
    Keywords: hydrogeological risk, climate change, prevention, environmental impact, territory. ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 113
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    Discriminating among distinct source models of the 1908 Messina Straits earthquake by modelling intensity data through full wavefield seismograms (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Macroseismic intensities are the only available data for most historical earthquakes and often represent the unique source of information for crucial events in the definition of seismic hazard. In this paper, we attempt at getting insight into source characteristics by reproducing the observed intensity field. As a test case, we study the source of 1908 Messina Straits earthquake ( M W = 7.1), by testing three distinct fault models deduced from the analysis of geodeticdata.Startingfromthestaticslipdistribution,wedevelop kinematicsourcemodelsfor the investigated fault and compute full waveform synthetic seismograms in a 1-D structural model, also accounting for anelastic attenuation. Then, we convert both computed peak- ground acceleration (PGA) and peak-ground velocity (PGV) to macroseismic intensity at 100 selected sites, by means of specific empirical relations for the Italian region. By comparing the original data separately with PGA- and PGV-based intensity fields, we discriminate among the tested faults and determine the best values for the investigated kinematic parameters of the source. We also perform a misfit analysis for the best source model, in order to investigate the dependence of the results on the selected parametrization. The results of the analysis indicate that among the tested models, the one characterized by an east-dipping fault, with strike- oriented NS slightly rotated clockwise, better explains the observed macroseismic field of the 1908 Messina Straits earthquake. Besides, the fracture nucleated at the southern end of the fault and ruptured northward, producing considerable directivity effects. This is in agreement with the published results obtained from the investigation of the historical seismograms. We alsodeterminerealisticvalues fortherupturevelocityand therise-time.Ourstudyconfirms the greatpotentialofthemacroseismicdata,demonstratingthattheycontainenoughinformationto constrain important characteristics of the fault, which can be retrieved by using complex source models and computing complete wavefield. Moreover, we also show that the simultaneous comparison of both PGA- and PGV-based synthetic macroseismic fields with the original intensities provides tighter constraints for discriminating among different source models, with respect to what attainable from each of them
    Description: Published
    Description: 164-173
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions; Earthquake source observations. ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 114
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    Numerical evidences enabling to reconcile gravity and height changes in volcanic areas (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Gravity and height changes, reflecting magma accumulation in subsurface chambers, are evaluated using Finite Element models in order to resolve controversial relationships observed in some volcanic areas. When significant gravity changes occur without any significant deformation, or vice versa, it is often difficult, if not impossible, to jointly explain the observations using the popular Mogi model. Here we explore whether these discrepancies can be explained by magma compressibility and source geometry effects. Compression of resident magma and expansion of the chamber wall act concurrently to accommodate newly added magma. Gravity-height ratios are found to mainly depend on: (i) geometry of the sources, which control the volume expansion of the chamber, (ii) magma compressibility, which affects the contraction of the magma resident in the chamber, and (iii) depth of the sources. Our numerical results show that, when magma compressibility and non-spherical sources are taken into account, significant gravity variations can, indeed, be successfully reconciled with negligible height changes. This may be the case at Etna volcano, where gravity changes (about 40 miuGal) without any significant deformation (below 5 cm) were observed during the 1994-1995 inflation period. The numerical results point to the accumulation of a 1.4x10^10 kg mass into an elongated source simulating a shallow storage region supplying the summit craters.
    Description: Published
    Description: 164-173
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: numerical modeling, gravity and height changes ; 04. Solid Earth::04.03. Geodesy::04.03.05. Gravity variations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 115
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    On the present-day crustal stress, strain-rate fields and mantle anisotropy pattern of Italy (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present an up-to-date high resolution picture of the ongoing crustal deformation field of Italy, based on an extensive combination of permanent and non-permanent GPS observations carried out since 1994. In addition, we present an updated map of contemporary SHmax orientations computed by a multidisciplinary data set of well-constrained stress indicators, including both published results and novel analyses. The comparison of stress and geodetic strain-rates directions reveals that both patterns are near-parallel over a large part of the investigated area, highlighting that crustal stress and surface deformation are driven by the same mechanism. The comparison of the azimuthal patterns of surface strain and mantle deformation shows a modest correlation on the Alps and a low correlation along the Apennines chain and the Calabro-Peloritan Arc. Along the Apennines chain, this feature suggests the occurrence of significant strain partitioning and crust–mantle mechanical decoupling. Along the Calabro-Peloritan Arc, the apparent low correlation reflects a different mantle–crust mechanism of deformation to the ongoing subduction and rollback of the Ionian slab. In addition, the superposition of regional/local effects related to second-order sources (crustal lateral density changes, strength contrasts), which at regional/local scale modulate the crustal stress/strain-rate pattern, cannot be ruled out.
    Description: Published
    Description: 969-985
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Plate motions ; Seismic anisotropy ; Kinematics of crustal and mantle deformation ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
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  • 116
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    Seismic Q estimates in Umbria-Marche (central Italy): hints for the retrieval of a new attenuation law for seismic risk (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In the Umbria Marche (Central Italy) region an important earthquake sequence occurred in 1997, characterized by nine earthquakes with magnitudes in the range between 5 and 6, that caused important damages and causalities. In the present paper we separately estimate intrinsic- and scattering- Q −1 parameters, using the classical MLTWA approach in the assumption of a half space model. The results clearly show that the attenuation parameters Qi −1 and Qs −1 are frequency dependent. This estimate is compared with other attenuation studies carried out in the same area, and with all the other MLTWA estimates obtained till now in other tectonic environments in the Earth. The bias introduced by the half space assumption is investigated through numerical solutions of the Energy Transport equation in the more realistic assumption of a heterogeneous crust overlying a transparent mantle, with a Moho located at a depth ranging between 35 and 45 km below the surface. The bias introduced by the half space assumption is significant only at high frequency. We finally show how the attenuation estimates, calculated with different techniques, lead to different PGA decay with distance relationships, using the well known and well proven Boore’s method. This last result indicates that care must be used in selecting the correct estimate of the attenuation parameters for seismic risk purposes. We also discuss the reason why MLTWA may be chosen among all the other available techniques, due to its intrinsic stability, to obtain the right attenuation parameters.
    Description: Published
    Description: 1370-1382
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: open
    Keywords: Seismic attenuation ; scattering ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    The seismogenic structure of the 2013–2014 Matese seismic sequence, Southern Italy: implication for the geometry of the Apennines active extensional belt (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Seismological, geological and geodetic data have been integrated to characterize the seismogenic structure of the late 2013-early 2014 moderate energy (maximum local magnitude MLmax = 4.9) seismic sequence that struck the interior of the Matese Massif, part of the Southern Apennines active extensional belt. The sequence, heralded by a ML = 2.7 foreshock, was characterized by two main shocks with ML = 4.9 and ML = 4.2, respectively, which occurred at a depth of ∼17–18 km. The sequence was confined in the 10–20 km depth range, significantly deeper than the 1997–1998 sequence which occurred few km away on the northeastern side of the massif above ∼15 km depth. The depth distribution of the 2013–14 sequence is almost continuous, albeit a deeper (16–19 km) and a shallower (11–15 km) group of events can be distinguished, the former including the main shocks and the foreshock. The epicentral distribution formed a ∼10 km long NNW–SSE trending alignment, which almost parallels the surface trace of late Pliocene–Quaternary southwest-dipping normal faults with a poor evidence of current geological and geodetic deformation. We built an upper crustal model profile for the eastern Matese massif through integration of geological data, oil exploration well logs and seismic tomographic images. Projection of hypocentres on the profile suggests that the seismogenic volume falls mostly within the crystalline crust and subordinately within the Mesozoic sedimentary cover of Apulia, the underthrust foreland of the Southern Apennines fold and thrust belt. Geological data and the regional macroseismic field of the sequence suggest that the southwest-dipping nodal plane of the main shocks represents the rupture surface that we refer to here as the Matese fault. The major lithological discontinuity between crystalline and sedimentary rocks of Apulia likely confined upward the rupture extent of the Matese fault. Repeated coseismic failure represented by the deeper group of events in the sequence, activated in a passive fashion the overlying ∼11–15 km deep section of the upper crustal normal faults. We consider the southwest-dipping Matese fault representative of a poorly known type of seismogenic structures in the Southern Apennines, where extensional seismogenesis and geodetic strain accumulation occur more frequently on NE-dipping, shallower-rooted faults. This is the case of the Boiano Basin fault located on the northern side of the massif, to which the 1997–1998 sequence is related. The close proximity of the two types of seismogenic faults at the Matese Massif is related to the complex crustal architecture generated by the Pliocene–early Pleistocene contractional and transpressional tectonics.
    Description: Published
    Description: 823-837
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: partially_open
    Keywords: Seismicity and tectonics ; Continental tectonics: extensional ; Crustal structure ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 118
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    Empirical conversion between teleseismic magnitudes (mb and Ms) and moment magnitude (Mw) at the Global, Euro-Mediterranean and Italian scale (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We analysed the conversion problem between teleseismic magnitudes (Ms and mb) provided by the Seismological Bulletin of the International Seismological Centre and moment magni- tudes (Mw) provided by online moment tensor (MT) catalogues using the chi-square general orthogonal regression method (CSQ) that, differently from the ordinary least-square regres- sion method (OLS), accounts for the measurement errors of both the predictor and response variables. To account for the non-linearity of the relationships, we used two types of curvilin- ear models: (i) the exponential model (EXP), recently proposed by the authors of the Global Catalogue sponsored by the Global Earthquake Model (GEM) Foundation and (ii) a connected bilinear (CBL) model, similar to that proposed by Ekstro ̈m & Dziewonski, where two different linear trends at low and high magnitudes are connected by an arc of circle that preserves the continuity of the function and of its first derivative at the connecting points. For Ms, we found that the regression curves computed for a global data set (GBL) are likely to be biased by the incompleteness of global MT catalogues for Mw 〈5.0–5.5. In fact, the GBL curves deviate significantly from a similar regression curve computed for a Euro-Mediterranean data set (MED) integrated with the data provided by two regional MT catalogues including many more events with Mw 〈 5.0–5.5. The GLB regression curves overestimate the Mw proxies computed from Ms up to 0.5 magnitude units. Hence for computing Mw proxies at the global scale of Ms ≤ 5.5, we suggest to adopt the coefficients obtained from the MED regression. The analysis of the frequency–magnitude relationship of the resulting Mw proxy catalogues confirms the validity of this choice as the behaviour of b-value as a function of cut-off magnitude of the GBL data set is much more stable using such approach. The incompleteness of Mw’s provided from MT global catalogues also affects the mb GBL data set but in this case the use of the CSQ regression method, in place of the OLS, mitigates the bias and then, at low magnitudes, the EXP regression curve computed from the more complete MED data set almost coincides with that computed from the GBL data set. Our results also indicate that the slope at low magnitudes of the Mw–Ms relationship is substantially consistent with the hypothesized theoretical value of 2/3 for Ms 〈 5.0 while the slope of the Mw–mb relationship at high magnitudes probably reaches the theoretically expected value of 2 only in the proximity of the upper limit of mb determinations in our data set (mb = 7.2).
    Description: Published
    Description: 805–828
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations ; Statistical seismology ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
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  • 119
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    Comment on ‘Are the source models of the M 7.1 1908 Messina Straits earthquake reliable? Insights from a novel inversion and sensitivity analysis of levelling data’ by M. Aloisi, V. Bruno, F. Cannav ` o, L. Ferranti, M. Mattia, C. Monaco and M. Palano (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In a recent paper, important issues were raised about the identification of the fault responsible for the 1908 Messina Straits earthquake. Starting with a reanalysis of the available original geodetic data, the authors aimed to demonstrate that both of the fault–plane orientations derived by the focal mechanism are compatible with the measurements. On these grounds, and based on geological considerations, they argued in favour of the Armo fault—a high-angled structure on the Calabrian side of the Messina Straits—as responsible for the 1908 earthquake. We indicate here that their analysis has some pitfalls that produce questionable results, and that render their conclusions unreliable. Moreover, especially when dealing with such old events and data, we consider that it is more prudent not to derive conclusions on the basis of a single data set, as all of the available information should be included in any interpretation. Indeed, when the joint results of the seismological and geodetic analyses are taken into account, a consistent and robust source model can be derived that indicates that a low-angle, east-dipping fault is the most likely source of this 1908 Messina Straits earthquake
    Description: Published
    Description: 1399-1402
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations; Seismicity and tectonics; Europe ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 120
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    Deformation of the western Indian plate boundary: insights from differential and multi-aperture InSAR data inversion of the 2008, Baluchistan (Western Pakistan) seismic sequence (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In this study,we use Differential Synthetic Aperture Radar Interferometry (DInSAR) and multiaperture interferometry (MAI) to constrain the sources of the three largest events of the 2008 Baluchistan (western Pakistan) seismic sequence, namely two Mw 6.4 events only 12 hr apart and an Mw 5.7 event that occurred 40 d later. The sequence took place in the Quetta Syntaxis, the most seismically active region of Baluchistan, tectonically located between the colliding Indian Plate and the Afghan Block of the Eurasian Plate. Surface displacements estimated from ascending and descending ENVISAT ASAR acquisitions were used to derive elastic dislocation models for the sources of the two main events. The estimated slip distributions have peak values of 120 and 130 cm on a pair of almost parallel and near-vertical faults striking NW–SE, and of 50 cm and 60 cm on two high-angle faults striking NE–SW. Values up to 50 cm were found for the largest aftershock on an NE–SW fault located between the sources of the main shocks. The MAI measurements, with their high sensitivity to the north–south motion component, are crucial in this area to accurately describe the coseismic displacement field. Our results provide insight into the deformation style of the Quetta Syntaxis, suggesting that right-lateral slip released at shallow depths on large NW fault planes is compatible with left-lateral activation on smaller NE–SW faults.
    Description: Published
    Description: 25-39
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Radar interferometry ; Satellite geodesy ; Seismicity and Tectonics ; Continental margins: convergent ; Earthquake interaction, forecasting and prediction ; Earthquake source observation ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 121
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    Prediction of the shear wave velocity Vs from CPT and DMT at research sites (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: The paper examines the correlations to obtain rough estimates of the shear wave velocity VS from nonseismic dilatometer tests (DMT) and cone penetration tests (CPT). While the direct measurement of VS is obviously preferable, these correlations may turn out useful in various circumstances. The experimental results at six international research sites suggest that the DMT predictions of VS from the parameters ID (material index), KD (horizontal stress index), MDMT (constrained modulus) are more reliable and consistent than the CPT predictions from qc (cone resistance), presumably because of the availability, by DMT, of the stress history index KD.
    Description: Published
    Description: 83-92
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: N/A or not JCR
    Description: restricted
    Keywords: horizontal stress index ; shear wave velocity ; flat dilatometer test ; cone penetration test ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 122
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    Monitoring of crustal seismic velocity variations in the L'Aquila fault zone inferred from noise cross-correlation (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The relative seismic velocity variations possibly associated to large earthquakes can be readily monitored via cross-correlation of seismic noise. In a recently published study, more than 2 yr of continuous seismic records have been analysed from three stations surrounding the epicentre of the 2009 April 6, Mw 6.1 L’Aquila earthquake, observing a clear decrease of seismic velocities likely corresponding to the co-seismic shaking. Here, we extend the analysis in space, including seismic stations within a radius of 60 km from the main shock epicentre, and in time, collecting 5 yr of data for the six stations within 40 km of it. Our aim is to investigate how far the crustal damage is visible through this technique, and to detect a potential post-seismic recovery of velocity variations. We find that the co-seismic drop in velocity variations extends up to 40 km from the epicentre, with spatial distribution (maximum around the fault and in the north– east direction from it) in agreement with the horizontal co-seismic displacement detected by global positioning system (GPS). In the first few months after L’Aquila earthquake, the crust’s perturbation in terms of velocity variations displays a very unstable behaviour, followed by a slow linear recovery towards pre-earthquake conditions; by almost 4 yr after the event, the co-seismic drop of seismic velocity is not yet fully recovered. The strong oscillations of the velocity changes in the first months after the earthquake prevent to detect the fast exponential recovery seen by GPS data. A test of differently parametrized fitting curves demonstrate that the post-seismic recovery is best explained by a sum of a logarithmic and a linear term, suggesting that processes like viscoelastic relaxation, frictional afterlip and poroelastic rebound may be acting concurrently.
    Description: Published
    Description: 604-6011
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Time-series analysis; Interferometry; Computational seismology; Europe ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 123
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    Shear-wave velocity profile and seismic input derived from ambient vibration array measurements: the case study of downtown L'Aquila (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2019-12-13
    Description: Downtown L'Aquila suffered severe damage (VIII-IX EMS98 intensity) during the 2009 April 6 Mw 6.3 earthquake. The city is settled on a top flat hill, with a shear-wave velocity profile characterized by a reversal of velocity at a depth of the order of 50–100 m, corresponding to the contact between calcareous breccia and lacustrine deposits. In the southern sector of downtown, a thin unit of superficial red soils causes a further shallow impedance contrast that may have influenced the damage distribution during the 2009 earthquake. In this paper, the main features of ambient seismic vibrations have been studied in the entire city centre by using array measurements. We deployed six 2-D arrays of seismic stations and 1-D array of vertical geophones. The 2-D arrays recorded ambient noise, whereas the 1-D array recorded signals produced by active sources. Surface-wave dispersion curves have been measured by array methods and have been inverted through a neighbourhood algorithm, jointly with the H/V ambient noise spectral ratios related to Rayleigh waves ellipticity. We obtained shear-wave velocity (Vs) profiles representative of the southern and northern sectors of downtown L'Aquila. The theoretical 1-D transfer functions for the estimated Vs profiles have been compared to the available empirical transfer functions computed from aftershock data analysis, revealing a general good agreement. Then, the Vs profiles have been used as input for a deconvolution analysis aimed at deriving the ground motion at bedrock level. The deconvolution has been performed by means of EERA and STRATA codes, two tools commonly employed in the geotechnical engineering community to perform equivalent-linear site response studies. The waveform at the bedrock level has been obtained deconvolving the 2009 main shock recorded at a strong motion station installed in downtown. Finally, this deconvolved waveform has been used as seismic input for evaluating synthetic time-histories in a strong-motion target site located in the middle Aterno river valley. As a target site, we selected the strong-motion station of AQV 5 km away from downtown L'Aquila. For this site, the record of the 2009 L'Aquila main shock is available and its surface stratigraphy is adequately known making possible to propagate the deconvolved bedrock motion back to the surface, and to compare recorded and synthetic waveforms.
    Description: Published
    Description: 848–866
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Fourier analysis, Earthquake ground motions , Site effects ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 124
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    Perception of risk for volcanic hazard in Indian Ocean: La Réunion Island case study. (2015)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: In 2011 a research project on volcanic risk assessment at La Réunion Island (Project Aléa, Institute de Physique du Globe de Paris, France) was conducted in order to determine more efficient strategies to manage future volcanic crises. The project included the evaluation of volcanic scenarios through field and historical data analysis, as well as a survey on volcanic risk perception in resident population. A clear scientific information and an effective communication with public play a crucial role in risk mitigation strategies. In particular, the evaluation of the public perception during both volcanic crises and dormant periods is an important element in developing actions focused on specific social and cultural contexts. A questionnaire was developed based on the ones used in similar researches conducted on Italian active volcanoes. Items were designed to measure variables connected with personal perception of hazard and risk, trust in mitigation actions and in information received about these aspects. In addition, specific items related to the peculiarities of La Réunion Island environment were included. A total of 2,000 questionnaires were distributed taking into account factors such as the proximity to the volcano and the involvement of communities in recent volcanic emergencies. Main results coming out from this survey, if on the one hand show an adequate residents’ perception of natural hazards, on the other hand highlight their poor knowledge of the island’ active volcano, a similar lacking knowledge of emergency plan for volcanic crises, but also a high confidence in scientists to provide accurate and reliable information on volcanic risk and hazards in contrast with Local Authorities. Remarkable findings of this study assess some key elements that should be considered by the institutions in charge for defining policies aimed to volcanic risk mitigation and management of future volcanic crises.
    Description: Unpublished
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: reserved
    Keywords: risk perception, volcanic hazards ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 125
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    Tomography of core–mantle boundary and lowermost mantle coupled by geodynamics (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2020-05-27
    Description: We propose an innovative approach to mapping CMB topography from seismic P-wave trav- eltime inversions: instead of treating mantle velocity and CMB topography as independent parameters, as has been done so far, we account for their coupling by mantle flow, as formulated by Forte & Peltier. This approach rests on the assumption that P data are sufficiently sensitive to thermal heterogeneity, and that compositional heterogeneity, albeit important in localized regions of the mantle (e.g. within the D′′ region), is not sufficiently strong to govern the pattern of mantle-wide convection and hence the CMB topography. The resulting tomographic maps of CMB topography are physically sound, and they resolve the known discrepancy between images obtained from classic tomography on the basis of core-reflected and core-refracted seismic phases. Since the coefficients of mantle velocity structure are the only free parameters of the inversion, this joint tomography–geodynamics approach reduces the number of param- eters; nevertheless the corresponding mantle models fit the seismic data as well as the purely seismic ones.
    Description: Published
    Description: 730-746
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic tomography ; 04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics
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  • 126
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    Palaeomagnetic analysis on pottery as indicator of the pyroclastic flow deposits temperature: new data and statistical interpretation from the Minoan eruption of Santorini, Greece (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present the results of palaeomagnetic analysis on Late Bronge Age pottery from Santorini carried out in order to estimate the thermal effect of the Minoan eruption on the pre-Minoan habitation level. A total of 170 specimens from 108 ceramic fragments have been studied. The ceramics were collected from the surface of the pre-Minoan palaeosol at six different sites, including also samples from the Akrotiri archaeological site. The deposition temperatures of the first pyroclastic products have been estimated by the maximum overlap of the re-heating temperature intervals given by the individual fragments at site level. A new statistical elaboration of the temperature data has also been proposed, calculating at 95 per cent of probability the re-heating temperatures at each site. The obtained results show that the precursor tephra layer and the first pumice fall of the eruption were hot enough to re-heat the underlying ceramics at temperatures 160–230 ◦C in the non-inhabited sites while the temperatures recorded inside the Akrotiri village are slightly lower, varying from 130 to 200 ◦C. The decrease of the temperatures registered in the human settlements suggests that there was some interaction between the buildings and the pumice fallout deposits while probably the buildings debris layer caused by the preceding and syn-eruption earthquakes has also contributed to the decrease of the recorded re-heating temperatures.
    Description: Published
    Description: 33-47
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Archaeomagnetism ; Rock and mineral magnetism ; Volcaniclastic deposits ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 127
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    Probabilistic hazard for seismically induced tsunamis: accuracy and feasibility of inundation maps (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Probabilistic tsunami hazard analysis (PTHA) relies on computationally demanding numerical simulations of tsunami generation, propagation, and non-linear inundation on high-resolution topo-bathymetric models. Here we focus on tsunamis generated by co-seismic sea floor dis- placement, that is, on Seismic PTHA (SPTHA). A very large number of tsunami simulations are typically needed to incorporate in SPTHA the full expected variability of seismic sources (the aleatory uncertainty). We propose an approach for reducing their number. To this end, we (i) introduce a simplified event tree to achieve an effective and consistent exploration of the seismic source parameter space; (ii) use the computationally inexpensive linear approximation for tsunami propagation to construct a preliminary SPTHA that calculates the probability of maximum offshore tsunami wave height (H Max) at a given target site; (iii) apply a two-stage filtering procedure to these ‘linear’ SPTHA results, for selecting a reduced set of sources and (iv) calculate ‘non-linear’ probabilistic inundation maps at the target site, using only the selected sources. We find that the selection of the important sources needed for approximating probabilistic inundation maps can be obtained based on the offshore HMax values only. The filtering procedure is semi-automatic and can be easily repeated for any target sites. We describe and test the performances of our approach with a case study in the Mediterranean that considers potential subduction earthquakes on a section of the Hellenic Arc, three target sites on the coast of eastern Sicily and one site on the coast of southern Crete. The comparison between the filtered SPTHA results and those obtained for the full set of sources indicates that our approach allows for a 75–80 per cent reduction of the number of the numerical simulations needed, while preserving the accuracy of probabilistic inundation maps to a reasonable degree.
    Description: Published
    Description: 574-588
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Tsunami ; Hazard ; Probabilistic ; Subduction ; Mediterranean ; SPTHA ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 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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  • 128
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    Assessment of resolution and accuracy of the Moving Window Cross Spectral technique for monitoring crustal temporal variations using ambient seismic noise (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Temporal variations in the elastic behaviour of the Earth’s crust can be monitored through the analysis of the Earth’s seismic response and its evolution with time. This kind of analysis is particularly interesting when combined with the reconstruction of seismic Green’s functions from the cross-correlation of ambient seismic noise, which circumvents the limitations imposed by a dependence on the occurrence of seismic events. In fact, because seismic noise is recorded continuously and does not depend on earthquake sources, these cross-correlation functions can be considered analogously to records from continuously repeating doublet sources placed at each station, and can be used to extract observations of variations in seismic velocities. These variations, however, are typically very small: of the order of 0.1 per cent. Such accuracy can be only achieved through the analysis of the full reconstructed waveforms, including later scattered arrivals. We focus on the method known as Moving-Window Cross-Spectral Analysis that has the advantage of operating in the frequency domain, where the bandwidth of coherent signal in the correlation function can be clearly defined. We investigate the sensitivity of this method by applying it to microseismic noise cross-correlations which have been perturbed by small synthetic velocity variations and which have been randomly contaminated. We propose threshold signal-to-noise ratios above which these perturbations can be reliably observed. Such values are a proxy for cross-correlation convergence, and so can be used as a guideline when determining the length of microseismic noise records that are required before they can be used for monitoring with the moving-window cross-spectral technique.
    Description: Published
    Description: 867-882
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Interferometry; Volcano monitoring ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
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    Up-dip directivity in near-source during the 2009 L'Aquila main shock (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In this study we have investigated the forward directivity associated with the initial up-dip rupture propagation during the April 6th 2009 (MW 6.1) L’Aquila normal-faulting earthquake. The objective is the understanding of how the peculiar initial behavior of rupture history during the main shock has affected the near-source recorded ground motions in the L’Aquila town and surrounding areas. We have modeled the observed ground velocities at the closest near-source recording sites by computing synthetic seismograms using a discrete wavenumbers and finite difference approach in the low frequency bandwidth (0.02-0.4 Hz) to avoid site effects contaminations. We use both the rupture model retrieved by inverting ground motion waveforms and continuous high sampling-rate GPS time series as well as uniform-slip constant-rupture speed models. Our results demonstrate that the initial up-dip rupture propagation, characterizing the first three seconds of the rupture history during the L’Aquila main shock and releasing only ∼25% of total seismic moment, controls the observed ground motions in the near-source. This initial stage of the rupture is characterized by the generation of clear ground velocity pulses, which we interpret as a forward directivity effect. Our modeling results confirm a heterogeneous distribution of rupture velocity during the initial up-dip rupture propagation, since uniform rupture speed models overestimate up-dip directivity effects in the footwall of the causative fault. The up-dip directivity observed in the near field during the 2009 L’Aquila main shock is that predicted for a normal faulting earthquake by Somerville’s directivity model, but it differs from that inferred from far-field observations that conversely provide evidence of along-strike directivity. This calls for a careful analysis as well as for the realistic inclusion of rupture directivity to predict ground motions in the near source.
    Description: Published
    Description: 1618-1631
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: earthquake ground motion, earthquake source observations, computational seismology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 130
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    Comment on ‘Magnitude conversion problem using general orthogonal regression’ by H. R. Wason, Ranjit Das and M. L. Sharma, (Geophys. J. Int., 190, 1091–1096) (2015)
    Wiley-Blackwell
    In:  Magnitude conversion problem using general orthogonal regression’ by H. R. Wason, Ranjit Das and M. L. Sharma, (Geophys. J. Int., 190, 1091–1096)
    Details
    Publication Date: 2017-04-04
    Description: The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.g. Ms or mb) to another (e.g. Mw), using the coefficients computed by the general orthogonal regression method (Fuller) is biased if the observed values of the predictor (independent) variable are used in the equation as well as the methodology they suggest to estimate the supposedly true values of the predictor variable are wrong for a number of theoretical and empirical reasons. Hence, we advise against the use of such methodology for magnitude conversions.
    Description: Published
    Description: 626-627
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations ; Statistical seismology ; Computational seismology ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
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  • 131
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    Long-term TIR imagery processing for spatiotemporal monitoring of surface thermal features in volcanic environment: A case study in the Campi Flegrei (Southern Italy) (2015)
    Wiley
    Details
    Publication Date: 2017-04-04
    Description: Different procedures were used to analyze a comprehensive time series of nighttime thermal infrared images acquired from October 2006 to June 2013 by a permanent station at Pisciarelli (Campi Flegrei, Italy). The methodologies were aimed at the detection and quantification of possible spatiotemporal changes in the ground-surface thermal features of an area affected by diffuse degassing. Long-term infrared time series images were processed without taking into account atmospheric conditions and emissivity estimations. The data obtained were compared with the trends of independent geophysical and geochemical parameters, which suggested that long-term temporal variations of the surface maximum temperatures were governed by the dynamics of the deeper hydrothermal system. Analogously, the dynamics of the shallow hydrothermal system are likely to control the short-period thermal oscillations that overlie the long-term thermal signals. The map of the yearly rates of temperature change shows temperature increases clustered in the thermal anomalous area of the infrared images, without evidence of modifications to the extension of the anomaly or of growth of new areas with significant thermal emission. This suggests that in the present state, the heat transfer is mainly due to hot gas emission through preexisting fractures and vents. Our data indicate that the comprehensive picture of the spatiotemporal evolution of the thermal features of the hydrothermal sites obtained by long-term infrared monitoring can provide useful information toward refining physical and conceptual models, as well as improving surveillance of active volcanoes.
    Description: The TIR monitoring system was partially funded by the 2000–2006 National Operating Programme and by the Italian Civil Protection Department in the framework of the 2004–2006 agreement with the Istituto Nazionale di Geofisica e Vulcanologia.
    Description: Published
    Description: 812–826
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 5V. Sorveglianza vulcanica ed emergenze
    Description: JCR Journal
    Description: restricted
    Keywords: Thermal Infrared Monitoring ; Campi Flegrei ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
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  • 132
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    Engineering Geology for Society and Territory - Volume 7: Education, Professional Ethics and Public Recognition of Engineering Geology (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: This book is one out of 8 IAEG XII Congress volumes, and deals with education and the professional ethics, which scientists, regulators, and practitioners of engineering geology inevitably have to face through the purposes, methods, limitations, and findings of their works. This volume presents contributions on the professional responsibilities of engineering geologists; the interaction of engineering geologists with other professionals; recognition of the engineering geological profession and its particular contribution to society, culture, and economy; and implications for the education of engineering geologists at tertiary level and in further education schemes. Issues treated in this volume are: the position of engineering geology within the geo-engineering profession; professional ethics and communication; resource use and re-use; managing risk in a litigious world; engineering and geological responsibility; and engineering geology at tertiary level. The Engineering Geology for Society and Territory volumes of the IAEG XII Congress held in Torino from September 15-19, 2014, analyze the dynamic role of engineering geology in our changing world and build on the four main themes of the congress: Environment, processes, issues, and approaches.
    Description: Published
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 5A. Energia e georisorse
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: open
    Keywords: Geoethics ; Geoeducation ; Professional Ethics ; Engineering Geology ; Communication ; Society ; Risks management ; Georesources ; Geological responsibility ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
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  • 133
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    Natural Gas Seepage (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Published
    Description: 7A. Geofisica di esplorazione
    Description: reserved
    Keywords: Gas seepage, methane ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 134
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    Fluid pressure waves trigger earthquakes (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Fluids—essentially meteoric water—are present everywhere in the Earth’s crust, occasionally also with pressures higher than hydrostatic due to the tectonic strain imposed on impermeable undrained layers, to the impoundment of artificial lakes or to the forced injections required by oil and gas exploration and production. Experimental evidence suggests that such fluids flow along preferred paths of high diffusivity, provided by rock joints and faults. Studying the coupled poroelastic problem, we find that such flow is ruled by a nonlinear partial differential equation amenable to a Barenblatt-type solution, implying that it takes place in formof solitary pressure waves propagating at a velocity which decreases with time as v ∝t [1/(n − 1) − 1] with n 7. According to Tresca-Von Mises criterion, these waves appear to play a major role in earthquake triggering, being also capable to account for aftershock delay without any further assumption. The measure of stress and fluid pressure inside active faults may therefore provide direct information about fault potential instability.
    Description: Published
    Description: 1281–1285
    Description: 6T. Sismicità indotta e caratterizzazione sismica dei sistemi naturali
    Description: N/A or not JCR
    Description: restricted
    Keywords: forecasting and prediction ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 135
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    Geosystemics, entropy and criticality of earthquakes: a vision of our planet and a key of access (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Earth is a system of interconnected systems, whose complexity is far from being fully understood by a reductionist approach alone. In this chapter we introduce the concept of geosystemics and the use of the entropy to characterize some aspects of the phenomena under study. We will show how entropy and criticality of the system are central to better understand the most important general features of earthquakes. We will analyze two recent seismic sequences culminated with a main-shock (2009 L’Aquila and 2012 Emilia, both in Italy) to show the potential of this approach and to understand some important characteristics of the seismicity under scrutiny.
    Description: Published
    Description: 3-20
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: restricted
    Keywords: geosystemics, earthquake, complexity ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
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  • 136
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    Geoethical aspects in the natural hazards management (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: The defence against natural hazards involves many actors with different roles: geoscientists, decision makers, local authorities, mass media, citizens. A proper management of georisks requires that each role is well-defined and governed by shared operational protocols, especially during the emergency phase, so that overlapping and misunderstanding don’t jeopardize population safety and economic activities. To achieve good results in this direction, it is necessary to undertake a careful evaluation of the limits and expectations of each component of society and the respect of legitimate aspirations and prerogatives. An effective defence system against natural hazards should be planned rationally and based on scientific data, in order to avoid alarmism among citizens, misleading sensationalism by media, careless decisions by politicians, as well as approximation in managing different phases of the risk cycle. Taking into consideration geoethical aspects related to natural hazards can be helpful to make geoscientists aware of their responsibilities towards society and to clarify the role they can play in the interaction with other actors, aiming at more efficacious actions for georisk mitigation.
    Description: Published
    Description: 59-62
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: 4V. Vulcani e ambiente
    Description: 4A. Clima e Oceani
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: restricted
    Keywords: Geoethics ; Natural hazards ; Risks ; Society ; Responsibility ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
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  • 137
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    What’s the seismic risk perception in Italy? (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Risk perception is a fundamental element in the definition and the adoption of preventive counter-measures. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. This paper presents preliminary results of a survey on seismic risk perception in Italy. The research design combines a psychometric and a cultural theoretic approach. More than 5,000 on-line tests have been compiled from January 23rd till July 25th, 2013. The data collected show that in Italy seismic risk perception is strongly underestimated; 86 on 100 Italian citizens, living in the most dangerous zone (namely Zone 1), do not have a correct perception of seismic hazard. From these observations we deem that extremely urgent measures are required in Italy to reach an effective way to communicate seismic risk"This study has benefited from funding provided by the Italian Presidenza del Consiglio dei Ministri - Dipartimento di Protezione Civile (DPC). This paper does not necessarily represent DPC official opinion and policies".
    Description: Published
    Description: 69-75
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: open
    Keywords: Risk perception ; Seismic hazard ; Hazard communication ; Seismic risk ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 138
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    Natural tritium determination in groundwater on Mt. Etna (Sicily, Italy) (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Tritium is a naturally occurring radionuclide, due to interactions of cosmic-rays with the upper layers of the atmosphere; but its presence in the environment is mainly due to residual fallout from nuclear weapons atmosphere tests, carried out from 1952 till 1980. Tritium reaches the Earth’s surface mainly in the form of precipitation, becoming part of the hydrological cycle, then the interest of tritium content analysis in drinking water is both for dosimetry and health-risk and for using tritium as a natural tracer in the groundwater circulation system. This paper presents results from a survey carried out in the Mt. Etna area (east and west flanks) and in the southern side of Nebrodi in Sicily (Italy), in order to determine tritium activity concentrations in water samples by using liquid scintillation counter. The investigated areas show quite low tritium concentrations, much below the Italian limit of 100 Bq L-1 for drinking water and even comparable with the minimum detectable activity value. The effective dose due to tritium for public drinking water consumption was also evaluated.
    Description: Published
    Description: 861-866
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: JCR Journal
    Description: restricted
    Keywords: Tritium ; Tritiated water ; Liquid scintillation ; Mt. Etna ; Drinking water ; 03. Hydrosphere::03.04. Chemical and biological::03.04.07. Radioactivity and isotopes
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  • 139
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    Projected Changes in Discharge in an Agricultural Watershed in Iowa (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Our improved capability to adapt to future changes in discharge is linked to our capability to predict the magnitude or at least the direction of these changes. For the agricultural U.S. Midwest, too much or too little water has severe socio-economic impacts. Here we focus on the Raccoon River at Van Meter, Iowa, and use a statistical approach to examine projected changes in discharge. We build on statistical models using rainfall and harvested corn and soybean acreage to explain the observed discharge variability. We then use projections of these two predictors to examine the projected discharge response. Results are based on seven global climate models part of the Coupled Model Intercomparison Project Phase 5 and two representative concentration pathways (RCPs 4.5 and 8.5). There is not a strong signal of change in the discharge projections under the RCP 4.5. However the results for the RCP 8.5 point to a stronger changing signal related to larger projected increases in rainfall, resulting in increasing trends in particular in the upper part of the discharge distribution (i.e., 60th percentile and above). Examination of two hypothetical agricultural scenarios indicates that these increasing trends could be alleviated by decreasing the extent of the agricultural production. We also discuss how the methodology presented in this study represents a viable approach to move forward with the concept of return period for engineering design and management in a non-stationary world.
    Description: Published
    Description: 1361–1371
    Description: 4A. Clima e Oceani
    Description: JCR Journal
    Description: restricted
    Keywords: river discharge ; rainfall ; statistical model ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
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  • 140
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    Archeoseismology in Sicily: past earthquakes and effects on society (2015)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: This work presents a review of archeological evidence of strong earthquakes occurring in Sicily at a time of Greek and Roman colonization, a period of considerable political, economic and social instability. In this historical context, the earthquake effects may have been obscured or overlooked to some extent and consequently the documentary information on ancient earthquakes, when available, is often sparse and lacking objectivity. The studied cases combine historical and archaeological data together with the evidence of structural damage to archaeological sites. Looking into past, the vocation of archaeoseismology lies in the identification of past seismic events, and particularly what the ancient society knew on earthquakes, and what kind of seismic effects produced on buildings and sites.
    Description: Unpublished
    Description: 491-504
    Description: 2T. Tettonica attiva
    Description: restricted
    Keywords: Archaeoseismology ; Historical seismicity ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 141
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    A strategy to explore the topography-driven distortions in the tilt field induced by a spherical pressure source. The case of Mt. Etna. (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present a strategy to thoroughly investigate the effects of prominent topography on the surface tilt due to a spherical pressure source. We use Etna's topography as a case of study and, for different source positions, we compare the tilt fields calculated through (i) a 3-D boundary element method and (ii) analytical half-space solutions. We systematically determine (i) the source positions leading to the strongest tilt misfits when numerical and analytical results are compared and (ii) the surface areas where the strongest distortions in the tilt field are most likely to be observed. We also demonstrate that, under critical circumstances, in terms of respective positions of pressure source and observation points, results of inversion procedures aimed at retrieving the source parameters can be misleading, if tilt data are analysed using models that do not account for topography.
    Description: Published
    Description: 1471–1481
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Numerical approximations and analysis ; Transient deformation ; Volcano monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 142
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    Unmodelled magnetic contributions in satellite-based models (2016)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: A complex system of electric currents flowing in the ionosphere and magnetosphere originates from the interaction of the solar wind and the Interplanetary Magnetic Field (IMF) with the Earth’s magnetic field. These electric currents generate magnetic fields contributing themselves to those measured by both ground observatories and satellites. Here, low-resolution (1 Hz) magnetic vector data recorded between 1 March 2014 and 31 May 2015 by the recently launched Swarm constellation are considered. The core and crustal magnetic fields and part of that originating in the magnetosphere are removed from Swarm measurements using CHAOS-5 model. Low- and mid-latitude residuals of the geomagnetic field representing the ionospheric and the unmodelled magnetospheric contributions are investigated, in the Solar Magnetic frame, according to the polarity of IMF B y (azimuthal) and B z (north–south) components and to different geomagnetic activity levels. The proposed approach makes it possible to investigate the features of unmodelled contributions due to the external sources of the geomagnetic field. Results show, on one side, the existence of a relation between the analysed residuals and IMF components B y and B z , possibly due to the long distance effect of high-latitude field-aligned currents. On the other side, they suggest the presence of a contribution due to the partial ring current that is activated during the main phase of geomagnetic storms. The perturbation observed on residuals is also compatible with the effect of the net field-aligned currents. Moreover, we have quantitatively estimated the effect of these current systems on computed residuals.
    Description: Published
    Description: 108
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: Swarm magnetic vector data ; Interplanetary Magnetic Field ; Magnetic models ; Field-aligned currents ; Partial ring current ; 01. Atmosphere::01.03. Magnetosphere::01.03.99. General or miscellaneous ; 01. Atmosphere::01.03. Magnetosphere::01.03.02. Magnetic storms ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 05. General::05.07. Space and Planetary sciences::05.07.01. Solar-terrestrial interaction
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  • 143
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    Annual Acoustic Presence of Fin Whale (Balaenoptera physalus) Offshore Eastern Sicily, Central Mediterranean Sea (2016)
    Public Library of Science
    Details
    Publication Date: 2017-04-04
    Description: In recent years, an increasing number of surveys have definitively confirmed the seasonal presence of fin whales (Balaenoptera physalus) in highly productive regions of the Mediterranean Sea. Despite this, very little is yet known about the routes that the species seasonally follows within the Mediterranean basin and, particularly, in the Ionian area. The present study assesses for the first time fin whale acoustic presence offshore Eastern Sicily (Ionian Sea), throughout the processing of about 10 months of continuous acoustic monitoring. The recording of fin whale vocalizations was made possible by the cabled deep-sea multidisciplinary observatory, “NEMO-SN1”, deployed 25 km off the Catania harbor at a depth of about 2,100 meters. NEMO-SN1 is an operational node of the European Multidisciplinary Seafloor and water-column Observatory (EMSO) Research Infrastructure. The observatory was equipped with a low-frequency hydrophone (bandwidth: 0.05 Hz–1 kHz, sampling rate: 2 kHz) which continuously acquired data from July 2012 to May 2013. About 7,200 hours of acoustic data were analyzed by means of spectrogram display. Calls with the typical structure and patterns associated to the Mediterranean fin whale population were identified and monitored in the area for the first time. Furthermore, a background noise analysis within the fin whale communication frequency band (17.9–22.5 Hz) was conducted to investigate possible detection-masking effects. The study confirms the hypothesis that fin whales are present in the Ionian Sea throughout all seasons, with peaks in call detection rate during spring and summer months. The analysis also demonstrates that calls were more frequently detected in low background noise conditions. Further analysis will be performed to understand whether observed levels of noise limit the acoustic detection of the fin whales vocalizations, or whether the animals vocalize less in the presence of high background noise.
    Description: Published
    Description: e0141838
    Description: 3A. Ambiente Marino
    Description: JCR Journal
    Description: open
    Keywords: Whales ; Bioacoustics ; Background noise (acoustics) ; Acoustic signals ; Sperm whales ; Vocalization ; Acoustics ; Data acquisition ; 03. Hydrosphere::03.01. General::03.01.08. Instruments and techniques ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring ; 03. Hydrosphere::03.02. Hydrology::03.02.07. Instruments and techniques ; 03. Hydrosphere::03.04. Chemical and biological::03.04.99. General or miscellaneous
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  • 144
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    New insights on the provenance of obsidian fragments of Ustica Island (Palermo, Sicily). (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-12-11
    Description: In this study we applied a multidisciplinary approach, coupling geophysical and geochemical measurements, to unveil the provenance of 170 obsidian flakes, collected on the volcanic island of Ustica (Sicily). On this island there are some prehistoric settlements dated from the Neolithic to the Middle Bronze Age. Despite not having geological outcrops of obsidian rocks, the countryside of Ustica is rich in fragments of this volcanic glass, imported from other source areas. The study of obsidian findings was carried out first through visual observations and density measurements. At least two different obsidian families have been distinguished, probably imported from Lipari and Pantelleria islands. Analysing the magnetic properties of the samples, these two main sources were confirmed, but the possibility of other provenances was inferred. Finally, we characterized the geochemical signature of the Ustica obsidians by performing microchemical analyses through electron microprobe (EMPA) and laser ablation (LA–ICP–MS). The results were compared with literature data, confirming the presence of the Lipari and Pantelleria sources (Sicily) and indicating for the first time in this part of Italy a third provenance from Palmarola island (Latium). Our results shed new light on the commercial exchanges in the peri-Tyrrhenian area during the prehistoric age.
    Description: Published
    Description: 435–454
    Description: 1SR. TERREMOTI - Servizi e ricerca per la Società
    Description: 2SR. VULCANI - Servizi e ricerca per la Società
    Description: 3SR. AMBIENTE - Servizi e ricerca per la Società
    Description: JCR Journal
    Description: restricted
    Keywords: obsdian provenance ; LA-ICPMS ; 05. General::05.04. Instrumentation and techniques of general interest::05.04.99. General or miscellaneous
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  • 145
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    A comparison of surface and underground array measurements of ambient noise recorded in Naples (Italy). (2015)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: Abstract In this study, we describe two experiments of seismic noise measurements carried out in Naples, Italy. The site allowed measurements to be obtained both at the surface and in a tunnel that is 120-m-deep. The main goal was to compare the seismic response evaluated at the surface to the in-tunnel response, through spectral, polarization, and resonance directivity analyses. In the 1 to 20 Hz frequency band, the noise level was up to 15 dB higher at the surface than in the tunnel. The polarization properties and horizontal-to-vertical spectral ratios appear not to be influenced by the tunnel geometry or by the topography. Some preferential alignments were observed in the polarization azimuths computed at the surface, which are likely to be due to local sources, rather than morphological features. The absence of directivity effects and the low noise levels in the tunnel make this site suitable for installing seismic stations. We also studied how the subsoil structure affects the seismic motion at the surface. The dispersive properties of the Rayleigh waves were investigated using the spatial autocorrelation method. A joint inversion of the dispersion data and the horizontal-to-vertical spectral ratios provided the subsurface Vs profile. The derived model has a low velocity contrast at depth, such as to generate moderate and broad H/V spectral ratio peak amplitude. The normalized spectral ratio appears more appropriate to identify the soil-resonance frequencies.
    Description: Published
    Description: 385 - 400
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: seismic noise ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 146
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    Seismic Microzonation in a Small Municipality: The Canazei Case Study (Trentino, N Italy) (2015)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: The results of a detailed seismic microzonation study performed at Canazei (Trentino—Northern Italy) are here presented. We investigated the local seismic response of this small village using a Level 3 seismic microzonation, the most accurate according to the Italian Code of Seismic Microzonation. This method consists of gradual steps of knowledge to consider different aspects of the amplification phenomena. A multidisciplinary approach has been performed, including a local geological study, geophysical investigations, geotechnical characterization of lithologies and numerical analyses. The obtained elastic response spectra were compared to the spectra prescribed by the Italian Building Code. Our results show the geologic and geophysical subsoil heterogeneities, responsible for different local seismic responses in terms of acceleration spectra and amplification factors.
    Description: Published
    Description: 1085-1089
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: reserved
    Keywords: Seismic microzonation ; Response spectra ; Amplification factor ; Canazei ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 147
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    Geoscientific Communication Problem with Communities for Disaster Prevention and Land Planning in Peru (2015)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: The communication process between the geoscientists and native communities in risk areas can significantly affect disaster prevention and land use planning. In Peru, the problem of disaster prevention is a fundamental policy due to unfamiliarity and deficiency of the associate information on the population. It is possible that talk of disaster prevention it will be an unlikely ideal in a country where most towns have settled on unplanned projects by the constant change and the lack of interest from the authorities in such topics. However, it is anachronistic that the rural communities and towns continue to live without a plan to enable them to improve their quality of life. The correct use of geoscience information in the mass media can help in this work. The characteristics of the enterprise in Peru require more training by professionals in the geosciences and support communication specialists. In this paper, we analyze the problem of communication for disaster prevention in Peru, with the aim of contributing to the articulation of a disaster prevention strategy.
    Description: Published
    Description: 81-83
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 4V. Vulcani e ambiente
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: reserved
    Keywords: Communication process ; Disaster prevention ; Risk management ; Peru ; Geoethics ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 148
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    Low-temperature catalytic CO2 hydrogenation with geological quantities of ruthenium: a possible abiotic CH4 source in chromitite-rich serpentinized rocks. (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2020-02-24
    Description: Metal-catalysed CO2 hydrogenation is considered a source of methane in serpentinized (hydrated) igneous rocks and a fundamental abiotic process germane to the origin of life. Iron, nickel, chromium and cobalt are the catalysts typically employed in hydrothermal simulation experiments to obtain methane at temperatures 〉200°C. However, land-based present-day serpentinization and abiotic gas apparently develop below 100°C, down to approximately 40–50°C. Here, we document considerable methane production in thirteen CO2 hydrogenation experiments performed in a closed dry system, from 20 to 90°C and atmospheric pressure, over 0.9–122 days, using concentrations of non-pretreated ruthenium equivalent to those occurring in chromitites in ophiolites or igneous complexes (from 0.4 to 76 mg of Ru, equivalent to the amount occurring approximately in 0.4–760 kg of chromitite). Methane production increased with time and temperature, reaching approximately 87 mg CH4 per gram of Ru after 30 days (2.9 mgCH4/gru/day) at 90°C. At room temperature, CH4 production rate was approximately three orders of magnitude lower (0.003 mgCH4/gru/day). We report the first stable carbon and hydrogen isotope ratios of abiotic CH4 generated below 100°C. Using initial d13CCO2 of -40&, we obtained room temperature d13CCH4 values as 13C depleted as 142&. With time and temperature, the C-isotope separation between CO2 and CH4 decreased significantly and the final d13CCH4 values approached that of initial d13CCO2. The presence of minor amounts of C2-C6 hydrocarbons is consistent with observations in natural settings. Comparative experiments at the same temperatures with iron and nichel catalysts did not generate CH4. Ru-enriched chromitites could potentially generate methane at low temperatures on Earth and on other planets.
    Description: Published
    Description: 438–452
    Description: 7A. Geofisica di esplorazione
    Description: JCR Journal
    Description: restricted
    Keywords: abiotic methane, Sabatier reaction ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 149
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    Considering uncertainties in the determination of earthquake source parameters from seismic spectra. (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2020-02-05
    Description: In this paper, we present a method for handling uncertainties in the determination of the source parameters of earthquakes from spectral data. We propose a robust framework for estimating earthquake source parameters and relative uncertainties, which are propagated down to the estimation of basic seismic parameters of interest such as the seismic moment, the moment magnitude, the source size and the static stress drop. In practice, we put together a Bayesian approach for model parameter estimation and a weighted statistical mixing of multiple solutions obtained from a network of instruments, providing a useful framework for extracting meaningful data from intrinsically uncertain data sets. The Bayesian approach used to estimate the source spectra parameters is a simple but powerful mechanism for non-linear model fitting, providing also the opportunity to naturally propagate uncertainties and to assess the quality and uniqueness of the solution. Another important added value of such an approach is the possibility of integrating information from the expertise of seismologists. Such data can be encoded in a prior state of information that is then updated with the information provided by seismological data. The performance of the proposed approach is demonstrated analysing data from the 1909 April 23 earthquake occurred near Benavente (Portugal).
    Description: Published
    Description: 691-701
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Fourier analysis ; Probability distributions ; Earthquake source observations ; Seismicity and tectonics ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
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  • 150
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    Glacial-to interglacial changes in nitrate supply and consumption in the subarctic North Pacific from microfossil-bound N isotopes at two trophic levels (2015)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 30, ISSN: 0883-8305
    Details
    Publication Date: 2015-11-09
    Repository Name: EPIC Alfred Wegener Institut
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  • 151
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    The Kongsfjorden Channel System offshore NW Svalbard: downslope sedimentary processes in a contour-current-dominated setting (2015)
    Springer
    In:  EPIC3Arktos, Springer, 1(1), ISSN: 2364-9453
    Details
    Publication Date: 2017-01-03
    Description: Submarine channel systems on and off glaciated continental margins can be up to hundreds of kilometres long, tens of kilometres wide and hundreds of metres deep. They result from repeated erosion and various downslope processes predominantly during glacial periods and can, therefore, provide valuable tools for the reconstruction of past ice-sheet dynamics. The Kongsfjorden Channel System (KCS) on the continental slope off northwest Svalbard provides evidence that downslope sedimentary processes are locally more dominant than regional along-slope sedimentation. It is a relatively short channel system (*120 km) that occurs at a large range of water depths (*250–4000 m) with slope gradients varying between 0 and 20. Multiple gullies on the Kongsfjorden Trough Mouth Fan merge to small channels that further merge to a main channel. The overall location of the channel system is controlled by variations in slope gradients and the ambient regional bathymetry. The widest and deepest incisions occur in areas of the steepest slope gradients. The KCS has probably been active since *1 Ma when glacial activity on Svalbard increased and grounded ice expanded to the shelf break off Kongsfjorden repeatedly. Activity within the system was probably highest during glacials. However, reduced activity presumably took place also during interglacials.
    Repository Name: EPIC Alfred Wegener Institut
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  • 152
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    Gas hydrate distribution and hydrocarbon maturation north of the Knipovich Ridge, western Svalbard margin (2016)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Solid Earth, Wiley, ISSN: 0148-0227
    Details
    Publication Date: 2016-02-02
    Description: A bottom-simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow-spreading ridge segment of the Mid Atlantic Ridge system. Here, heat flow is high (up to 330 mW m-2), increasing towards the ridge axis. The coinciding maxima in across-margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic-rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.
    Repository Name: EPIC Alfred Wegener Institut
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  • 153
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    Bias reduction in decadal predictions of West African monsoon rainfall using regional climate models (2016)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Atmospheres, Wiley, ISSN: 0148-0227
    Details
    Publication Date: 2019-07-17
    Description: The West African monsoon rainfall is essential for regional food production, and decadal predictions are necessary for policy makers and farmers. However, predictions with global climate models reveal precipitation biases. This study addresses the hypotheses that global prediction biases can be reduced by dynamical downscaling with a multimodel ensemble of three regional climate models (RCMs), a RCM coupled to a global ocean model and a RCM applying more realistic soil initialization and boundary conditions, i.e., aerosols, sea surface temperatures (SSTs), vegetation, and land cover. Numerous RCM predictions have been performed with REMO, COSMO-CLM (CCLM), and Weather Research and Forecasting (WRF) in various versions and for different decades. Global predictions reveal typical positive and negative biases over the Guinea Coast and the Sahel, respectively, related to a southward shifted Intertropical Convergence Zone (ITCZ) and a positive tropical Atlantic SST bias. These rainfall biases are reduced by some regional predictions in the Sahel but aggravated by all RCMs over the Guinea Coast, resulting from the inherited SST bias, increased westerlies and evaporation over the tropical Atlantic and shifted African easterly waves. The coupled regional predictions simulate high-resolution atmosphere-ocean interactions strongly improving the SST bias, the ITCZ shift and the Guinea Coast and Central Sahel precipitation biases. Some added values in rainfall bias are found for more realistic SST and land cover boundary conditions over the Guinea Coast and improved vegetation in the Central Sahel. Thus, the ability of RCMs and improved boundary conditions to reduce rainfall biases for climate impact research depends on the considered West African region.
    Repository Name: EPIC Alfred Wegener Institut
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  • 154
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    Late Miocene uplift of the North-East Greenland margin linked to plate tectonics: Seismic evidence from the Greenland Fracture Zone, NE Atlantic (2016)
    Wiley
    In:  EPIC3Tectonics, Wiley, 35(2), pp. 257-282, ISSN: 0278-7407
    Details
    Publication Date: 2016-03-25
    Description: Tectonic models predict that following breakup, rift margins undergo only decaying thermal subsidence during their postrift evolution. However, postbreakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to inner margin episodic uplift, including the formation of coastal mountains. The origin of these events remains enigmatic. We present a seismic reflection study from the Greenland Fracture Zone-East Greenland Ridge (GFZ-EGR) and the NE Greenland shelf. We document a regional intra-Miocene seismic unconformity (IMU), which marks the termination of synrift deposition in the deep-sea basins and onset of (i) thermomechanical coupling across the GFZ, (ii) basin compression, and (iii) contourite deposition, north of the EGR. The onset of coupling across the GFZ is constrained by results of 2-D flexural backstripping. We explain the thermomechanical coupling and the deposition of contourites by the formation of a continuous plate boundary along the Mohns and Knipovich ridges, leading to an accelerated widening of the Fram Strait. We demonstrate that the IMU event is linked to onset of uplift and massive shelf progradation on the NE Greenland margin. Given an estimated middle to late Miocene (~15–10Ma) age of the IMU, we speculate that the event is synchronous with uplift of the east and west Greenland margins. The correlation between margin uplift and plate motion changes further indicates that the uplift was triggered by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intraplate stresses related to global tectonics.
    Repository Name: EPIC Alfred Wegener Institut
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  • 155
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    Modelling climate change impacts on marine fish populations: process-based integration of ocean warming, acidification and other environmental drivers (2016)
    Wiley
    In:  EPIC3Fish and Fisheries, Wiley, pp. n/a-n/a, ISSN: 14672960
    Details
    Publication Date: 2017-03-10
    Description: Global climate change affects marine fish through drivers such as ocean warming, acidification and oxygen depletion, causing changes in marine ecosystems and socioeconomic impacts. While experimental and observational results can inform about anticipated effects of different drivers, linking between these results and ecosystem-level changes requires quantitative integration of physiological and ecological processes into models to advance research and inform management. We give an overview of important physiological and ecological processes affected by environmental drivers. We then provide a review of available modelling approaches for marine fish, analysing their capacities for process-based integration of environmental drivers. Building on this, we propose approaches to advance important research questions. Examples of integration of environmental drivers exist for each model class. Recent extensions of modelling frameworks increase the potential for including detailed mechanisms and improving model projections. Experimental results on energy allocation, behaviour and physiological limitations will advance the understanding of organism-level trade-offs and thresholds in response to multiple drivers. More explicit representation of life cycles and biological traits can improve description of population dynamics and adaptation, and data on food web topology and feeding interactions help to detail the conditions for possible regime shifts. Identification of relevant processes will also benefit the coupling of different models to investigate spatial–temporal changes in stock productivity and integrated responses of social–ecological systems. Thus, a more process-informed foundation for models will promote the integration of experimental and observational results and increase the potential for model-based extrapolations into a future under changing environmental conditions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 156
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    eVolutus: A New Platform for Evolutionary Experiments (2016)
    Springer
    In:  EPIC3Parallel Processing and Applied Mathematics, Parallel Processing and Applied Mathematics, Switzerland, Springer, 10 p., pp. 570-580, ISBN: 978-3-319-32151-6
    Details
    Publication Date: 2016-06-14
    Description: eVolutus is a new software platform designed for modeling evolutionary and population dynamics of living organisms. Single-celled eukaryotes, foraminifera, are selected as model organisms that have occupied the marine realm for at least 500 Ma and left an extraordinary fossil record preserved in microscopic shells. This makes them ideal objects for testing general evolutionary hypotheses based on studying multiscale genotypic, phenotypic, ecologic and macroevolutionary patterns. Our platform provides a highly configurable environment for conducting evolutionary experiments at various spatiotemporal scales.
    Repository Name: EPIC Alfred Wegener Institut
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  • 157
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    Reduced admixture of North Atlantic Deep Water to the deep central South Pacific during the last two glacial periods (2016)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 31, pp. 1-18, ISSN: 0883-8305
    Details
    Publication Date: 2016-11-15
    Description: The South Pacific is a sensitive location for the variability of the global oceanic thermohaline circulation given that deep waters from the Atlantic Ocean, the Southern Ocean, and the Pacific Basin are exchanged. Here we reconstruct the deep water circulation of the central South Pacific for the last two glacial cycles (from 240,000 years ago to the Holocene) based on radiogenic neodymium (Nd) and lead (Pb) isotope records complemented by benthic stable carbon data obtained from two sediment cores located on the flanks of the East Pacific Rise. The records show small but consistent glacial/interglacial changes in all three isotopic systems with interglacial average values of 5.8 and 18.757 for εNd and 206Pb/204Pb, respectively, whereas glacial averages are 5.3 and 18.744. Comparison of this variability of Circumpolar Deep Water (CDW) to previously published records along the pathway of the global thermohaline circulation is consistent with reduced admixture of North Atlantic Deep Water to CDW during cold stages. The absolute values and amplitudes of the benthic δ13C variations are essentially indistinguishable from other records of the Southern Hemisphere and confirm that the low central South Pacific sedimentation rates did not result in a significant reduction of the amplitude of any of the measured proxies. In addition, the combined detrital Nd and strontium (87Sr/86Sr) isotope signatures imply that Australian and New Zealand dust has remained the principal contributor of lithogenic material to the central South Pacific.
    Repository Name: EPIC Alfred Wegener Institut
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  • 158
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    The offshore East African Rift system: structural framework at the toe of a juvenile rift (2015)
    Wiley
    In:  EPIC3Tectonics, Wiley, 34, pp. 2086-2104, ISSN: 0278-7407
    Details
    Publication Date: 2015-11-21
    Description: The Cenozoic East African Rift System (EARS) extends from the Red Sea to Mozambique. Here we use seismic reflection and bathymetric data to investigate the tectonic evolution of the offshore branch of the EARS. The data indicate multiple and time transgressive neotectonic deformations along ~800km of the continental margin of northern Mozambique. We observe a transition from a mature rift basin in the north to a juvenile fault zone in the south. The respective timing of deformation is derived from detailed seismic stratigraphy. In the north, a ~30km wide and more than 150km long, N-S striking symmetric graben initiated as half-graben in the late Miocene. Extension accelerated in the Pliocene, causing a continuous conjugate border fault and symmetric rift graben. Coevally, the rift started to propagate southward, which resulted in a present-day ~30km wide half-graben, approximately 200km farther south. Since the Pleistocene, the rift has continued to propagate another ~300km, where the incipient rift is reflected by subrecent small-scale normal faulting. Estimates of the overall brittle extension of the matured rift range between 5 and 12km, with an along-strike southward decrease of the extension rate. The offshore portion of the EARS evolves magma poor, similar to the onshore western branch. The structural evolution of the offshore EARS is suggested to be related to and controlled by differing inherited lithospheric fabrics. Preexisting fabrics may not only guide and focus extension but also control rift architecture.
    Repository Name: EPIC Alfred Wegener Institut
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  • 159
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    A glimpse beneath Antarctic sea ice: platelet-layer volume from multi-frequency electromagnetic induction sounding (2016)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 43, ISSN: 0094-8276
    Details
    Publication Date: 2016-01-15
    Description: In Antarctica, ice crystals emerge from ice shelf cavities and accumulate in unconsolidated layers beneath nearby sea ice. Such sub-ice platelet layers form a unique habitat and serve as an indicator for the state of an ice shelf. However, the lack of a suitable methodology impedes an efficient quantification of this phenomenon on scales beyond point measurements. In this study, we inverted multifrequency electromagnetic (EM) induction soundings, obtained on fast ice with an underlying platelet layer along profiles of 〉100 km length in the eastern Weddell Sea. EM-derived platelet layer thickness and conductivity are consistent with other field observations. Our results suggest that platelet layer volume is higher than previously thought in this region and that platelet layer ice volume fraction is proportional to its thickness. We conclude that multifrequency EM is a suitable tool to determine platelet layer volume, with the potential to obtain crucial knowledge of associated processes in otherwise inaccessible ice shelf cavities.
    Repository Name: EPIC Alfred Wegener Institut
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  • 160
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    Environmental information for a marine ecosystem research approach for the northern Antarctic Peninsula (RV Polarstern expedition PS81, ANT-XXIX/3) (2016)
    Springer
    In:  EPIC3Polar Biology, Springer, 39(5), pp. 765-787, ISSN: 0722-4060
    Details
    Publication Date: 2017-01-12
    Description: During the austral summer expedition PS81, ANT-XXIX/3 with the German research ice breaker Polarstern in 2013, research was carried out to investigate the role of environmental factors on the distribution of benthic communities and marine mammal and krill densities around the northern tip of the Antarctic Peninsula. For these studies collated in this special issue and studies in this area, we present a collection of environmental parameters with probable influence on the marine ecosystems around the Antarctic Peninsula.
    Repository Name: EPIC Alfred Wegener Institut
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  • 161
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    Salt exchange in the Indian-Atlantic Ocean Gateway since the LGM: A compensating effect between Agulhas Current changes and salinity variations? (2015)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 30, ISSN: 0883-8305
    Details
    Publication Date: 2019-07-17
    Description: The import of relatively salty water masses from the Indian Ocean to the Atlantic is considered to be important for the operational mode of the Atlantic Meridional Overturning Circulation (AMOC). However, the occurrence and the origin of changes in this import behavior on millennial and glacial/interglacial timescales remains equivocal. Here we reconstruct multiproxy paleosalinity changes in the Agulhas Current since the Last Glacial Maximum and compare the salinity pattern with records from the Indian-Atlantic Ocean Gateway (I-AOG) and model simulations using a fully coupled atmosphere-ocean general circulation model. The reconstructed paleosalinity pattern in the Agulhas Current displays coherent variability with changes recorded in the wider I-AOG region over the last glacial termination. We infer that salinities simultaneously increased in both areas consistent with a quasi interhemispheric salt-seesaw response, analogous to the thermal bipolar seesaw in response to a reduced cross-hemispheric heat and salt exchange during times of weakened AMOC. Interestingly, these hydrographic shifts can also be recognized in the wider Southern Hemisphere, which indicates that salinity anomalies are not purely restricted to the Agulhas Current System itself. More saline upstream Agulhas waters were propagated to the I-AOG during Heinrich Stadial 1 (HS1). However, the salt flux into the South Atlantic might have been reduced due to a decreased volume transport through the I-AOG during the AMOC slowdown associated with HS1. Hence, our combined data-model interpretation suggests that intervals with higher salinity in the Agulhas Current source region are not necessarily an indicator for an increased salt import via the I-AOG into the South Atlantic.
    Repository Name: EPIC Alfred Wegener Institut
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  • 162
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    Recent foraminifera in the Arctic Ocean and Kara Sea continental margin (2015)
    Springer
    In:  EPIC3Arktos, Springer, pp. 0-17
    Details
    Publication Date: 2016-02-28
    Repository Name: EPIC Alfred Wegener Institut
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  • 163
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    Ocean temperature thresholds for Last Interglacial West Antarctic Ice Sheet collapse (2016)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2016-12-09
    Description: The West Antarctic Ice Sheet (WAIS) is considered the major contributor to global sea level rise in the Last Interglacial (LIG) and potentially in the future. Exposed fossil reef terraces suggest sea levels in excess of 7 meters in the last warm era, of which probably not much more than 2 meters are considered to originate from melting of the Greenland Ice Sheet. We simulate the evolution of the Antarctic Ice Sheet during the LIG with a 3D thermomechanical ice sheet model forced by an atmosphere ocean general circulation model (AOGCM). Our results show that high LIG sea levels, cannot be reproduced with the atmosphere-ocean forcing delivered by current AOGCMs. However, when taking reconstructed Southern Ocean temperature anomalies of several degrees, sensitivity studies indicate a Southern Ocean temperature anomaly threshold for total WAIS collapse of 2-3∘C, accounting for a sea level rise of 3-4 meters during the LIG. Potential future Antarctic Ice Sheet dynamics range from a moderate retreat to a complete collapse, depending on rate and amplitude of warming.
    Repository Name: EPIC Alfred Wegener Institut
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  • 164
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    Mg/Ca thermometry in planktic foraminifera: Improving paleotemperature estimations for G. bulloides and N. pachyderma left (2016)
    Wiley
    In:  EPIC3Geochemistry, Geophysics, Geosystems, Wiley, 17(4), pp. 1249-1264, ISSN: 15252027
    Details
    Publication Date: 2016-06-23
    Repository Name: EPIC Alfred Wegener Institut
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  • 165
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    Trophic Ecology and Habitat Provision in Cold-Water Coral Ecosystems (2016)
    Springer
    In:  EPIC3Marine Animal Forests, Marine Animal Forests, Switzerland, Springer, 26 p., pp. 1-26, ISBN: 978-3-319-17001-5
    Details
    Publication Date: 2017-01-27
    Description: Cold-water coral ecosystems differ from each other greatly in structure, faunal makeup, and ecological function. Attributes such as substrate type, 3-D complexity, biological community, and nutrient supply also change over small temporal and spatial scales. In this chapter, we present an overview of food gathering strategies employed by a range of cold-water corals. Furthermore, the importance of corals as habitat providers for associated fauna and thus biodiversity is discussed. The coral habitats support ecosystems at various spatial scales ranging from local exposed skeleton patches on gorgonian branches to the various zones on a reef. Comparison is made between many types of animal forests made up by cold-water corals, including several types of coral gardens and coastal and offshore reefs from a wide range of environmental settings. The trophic ecology of reef types is compared, and the variation in feeding behavior across particular reefs is also discussed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 166
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    Simulating soil organic carbon in yedoma deposits during the Last Glacial Maximum in a land surface model (2016)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 43(10), pp. 5133-5142, ISSN: 0094-8276
    Details
    Publication Date: 2016-09-19
    Description: Substantial quantities of organic carbon (OC) are stored in the thick, ice-rich, and organic-rich sediments called yedoma deposits, distributed in eastern Siberia and Alaska today. Quantifying yedoma carbon stocks during the glacial period is important for understanding how much carbon could have been decomposed during the last deglaciation. Yet processes that yield the formation of thick frozen OC in yedoma deposits are missing in global carbon cycle models. Here we incorporate sedimentation parameterizations into the Organizing Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE-MICT) land surface model, which leads to reasonable results in OC vertical distribution and regional budgets, compared with site-specific observations and inventories for today's nondegraded yedoma region. Simulated total soil OC stock for the northern permafrost region during the Last Glacial Maximum (LGM) is 1536–1592 Pg C, of which 390–446 Pg C is within today's yedoma region. This result is an underestimation since we did not account for the potentially much larger yedoma area during the LGM than the present day.
    Repository Name: EPIC Alfred Wegener Institut
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  • 167
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    Cyclic magnetite dissolution in Pleistocene sediments of the abyssal northwest Pacific Ocean: Evidence for glacial oxygen depletion and carbon trapping (2016)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 31, pp. 600-624, ISSN: 0883-8305
    Details
    Publication Date: 2018-08-10
    Repository Name: EPIC Alfred Wegener Institut
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  • 168
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    Status, trends and drivers of kelp forests in Europe: an expert assessment. (2016)
    Springer
    In:  EPIC3Biodivers Conserv, Springer, pp. 1-30
    Details
    Publication Date: 2016-06-16
    Description: A comprehensive expert consultation was conducted in order to assess the status, trends and the most important drivers of change in the abundance and geographical distribution of kelp forests in European waters. This consultation included an on-line questionnaire, results from a workshop and data provided by a selected group of experts working on kelp forest mapping and eco-evolutionary research. Differences in status and trends according to geographical areas, species identity and small-scale variations within the same habitat where shown by assembling and mapping kelp distribution and trend data. Significant data gaps for some geographical regions, like the Mediterranean and the southern Iberian Peninsula, were also identified. The data used for this study confirmed a general trend with decreasing abundance of some native kelp species at their southern distributional range limits and increasing abundance in other parts of their distribution (Saccharina latissima and Saccorhiza polyschides). The expansion of the introduced species Undaria pinnatifida was also registered. Drivers of observed changes in kelp forests distribution and abundance were assessed using experts’ opinions. Multiple possible drivers were identified, including global warming, sea urchin grazing, harvesting, pollution and fishing pressure, and their impact varied between geographical areas. Overall, the results highlight major threats for these ecosystems but also opportunities for conservation. Major requirements to ensure adequate protection of coastal kelp ecosystems along European coastlines are discussed, based on the local to regional gaps detected in the study.
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  • 169
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    Climate change and marine benthos: a review of existing research and future directions in the North Atlantic (2015)
    Wiley
    In:  EPIC3Wiley Interdisciplinary Reviews: Climate Change, Wiley, ISSN: 1757-7799
    Details
    Publication Date: 2015-01-20
    Description: There is growing evidence that climate change could affectmarine benthic systems. This review provides information of climate change-related impacts on the marine benthos in the North Atlantic. We cover a number of related research aspects, mainly in connection to two key issues. First, is the relationship between different physical aspects of climate change and the marine benthos. This section covers: (a) the responses to changes in seawater temperature (biogeographic shifts and phenology); (b) altered Hydrodynamics; (c) ocean acidification (OA); and (d) sea-level rise-coastal squeeze. The second major issue addressed is the possible integrated impact of climate change on the benthos. This work is based on relationships between proxies for climate variability, notably the North Atlantic Oscillation (NAO) index, and the long-term marine benthos. The final section of our review provides a series of conclusions and future directions to support climate change research on marine benthic systems.
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  • 170
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    Confocal Raman microscopy in sclerochronology: A powerful tool to visualize environmental information in recent and fossil biogenic archives (2015)
    Wiley
    In:  EPIC3Geochemistry, Geophysics, Geosystems, Wiley, 16
    Details
    Publication Date: 2015-02-10
    Description: Biological hard parts and skeletons of aquatic organisms often archive information of past environmental conditions. Deciphering such information forms an essential contribution to our understanding of past climate conditions and thus our ability to mitigate the climatic, ecological, and social impacts of a rapidly changing environment. Several established techniques enable the visualization and reliable use of the information stored in anatomical features of such biogenic archives, i.e., its growth patterns. Here, we test whether confocal Raman microscopy (CRM) is a suitable method to reliably identify growth patterns in the commonly used archive Arctica islandica and the extinct species Pygocardia rustica (both Bivalvia). A modern A. islandica specimen from Norway has been investigated to verify the general feasibility of CRM, resulting in highly correlated standardized growth indices (r〉0.96; p〈0.0001) between CRM-derived measurements and measurements derived from the established methods of fluorescence microscopy and Mutvei’s solution staining. This demonstrates the general suitability of CRM as a method for growth pattern evaluation and cross-dating applications. Moreover, CRM may be of particular interest for paleoenvironmental reconstructions, as it yielded superior results in the analysis of fossil shell specimens (A. islandica and P. rustica) compared to both Mutvei staining and fluorescence microscopy. CRM is a reliable and valuable tool to visualize internal growth patterns in both modern and fossil calcium carbonate shells that notably also facilitates the assessment of possible diagenetic alteration prior to geochemical analysis without geochemically compromising the sample. We strongly recommend the CRM approach for the visualization of growth patterns in fossil biogenic archives, where conventional methods fail to produce useful results.
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  • 171
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    Pteropod sedimentation patterns in different water depths observed with moored sediment traps over a 4-year period at the LTER station HAUSGARTEN in eastern Fram Strait (2015)
    Springer
    In:  EPIC3Polar Biol, Springer, ISSN: 0722-4000
    Details
    Publication Date: 2015-02-10
    Description: Pteropods are important organisms in highlatitude ecosystems, and they are expected to severely suffer from climate change in the near future. In this study, sedimentation patterns of two pteropod species, the polar Limacina helicina and the subarctic boreal L. retroversa, are presented. Time series data received by moored sediment traps at the Long-Term Ecological Research (LTER) Observatory HAUSGARTEN in eastern Fram Strait were analyzed during the years 2008 to 2012. Results were derived from four different deployment depths (200, 1,250, 2,400, and 2,550 m) at two different sites (79°N 04'200E; 79°430N 04'300E). A species-specific sedimentation pattern was present at all depths and at both sites showing maximal flux rates during September/October for L. helicina and in November/December for L. retroversa. The polar L. helicina was outnumbered by L. retroversa (55–99 %) at both positions and at all depths supporting the recently observed trend toward the dominance of the subarctic boreal species. The largest decrease in pteropod abundance occurred within the mesopelagic zone (*200–1,250 m), indicating loss via microbial degradation and grazing. Pteropod carbonate (aragonite) amounted up to *75 % of the total carbonate flux at 200 m and 2–13 % of the aragonite found in the shallow traps arrived at the deep sediment traps (*160 m above the seafloor), revealing the significance of pteropods in carbonate export at Fram Strait. Our results emphasize the relevance and the need for continuation of long-term studies to detect and trace changes in pteropod abundances and community composition and thus in the vertical transport of aragonite.
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  • 172
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    Annual changes of aerosol optical depth and Ångström exponent over Spitsbergen (2015)
    Springer
    In:  EPIC3Free Preview Impact of Climate Changes on Marine Environments, Book, Springer, 15 p., pp. 23-37, ISBN: 978-3-319-14282-1
    Details
    Publication Date: 2020-03-05
    Description: This book contributes to the current discussion on global environmental changes by discussing modifications in marine ecosystems related to global climate changes. In marine ecosystems, rising atmospheric CO2 and climate changes are associated with shifts in temperature, circulation, stratification, nutrient input, oxygen concentration and ocean acidification, which have significant biological effects on a regional and global scale. Knowing how these changes affect the distribution and abundance of plankton in the ocean currents is crucial to our understanding of how climate change impacts the marine environment. Ocean temperatures, weather and climatic changes greatly influence the amount and location of nutrients in the water column. If temperatures and currents change, the plankton production cycle may not coincide with the reproduction cycle of fish. The above changes are closely related to the changes in radiative forcing, which initiate feedback mechanisms like changes in surface temperature, circulation, and atmospheric chemistry.
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  • 173
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    Mineral dust variability in Antarctic ice for different climate conditions (2015)
    Springer
    In:  EPIC3Integrated Analysis of Interglacial Climate Dynamics, Springer Briefs in Earth System Sciences, Heidelberg, Springer, pp. 89-95, ISBN: 978-3-319-00692-5
    Details
    Publication Date: 2015-04-07
    Description: This study aims to understand the dust deposition changes on the Antarctic ice sheet in different climatic stages. To this end high resolution dust concentration and size profiles from the EPICA-DML ice core over the transition from the last Glacial to the Holocene (T1) were combined with model experiments for four interglacial time slices and the Last Glacial Maximum (LGM). A strong decrease in dust concentration (factor 46) and a slight increase in dust size was observed during T1. A strong coupling between transport and intensified sources during the Glacial could be derived from the seasonal variability of concentration and size and its phase-lag. This strong coupling vanishes during the Holocene. The model simulates increased dust deposition in Antarctica for all past interglacial time slices compared to the pre-industrial period. The major cause for the increase is enhanced Southern Hemisphere dust emission, but changes in atmospheric transport are also relevant. The maximum dust deposition in Antarctica is simulated for the LGM, showing a 10-fold increase compared to preindustrial conditions.
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  • 174
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    Cell-vertex discretization of shallow water equations on mixed unstructured meshes (2015)
    Springer
    In:  EPIC3Ocean Dynamics, Springer, 65(1), pp. 33-47, ISSN: 1616-7341
    Details
    Publication Date: 2015-02-10
    Description: Finite-volume discretizations can be formulated on unstructured meshes composed of different polygons. A staggered cell-vertex finite-volume discretization of shallow water equations is analyzed on mixed meshes composed of triangles and quads. Although triangular meshes are most flexible geometrically, quads are more efficient numerically and do not support spurious inertial modes of triangular cell- vertex discretization. Mixed meshes composed of triangles and quads combine benefits of both. In particular, triangular transitional zones can be used to join quadrilateral meshes of differing resolution. Based on a set of examples involving shallow water equations, it is shown that mixed meshes offer a viable approach provided some background biharmonic viscosity (or the biharmonic filter) is added to stabilize the triangular part of the mesh.
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  • 175
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    Snow Accumulation In North Greenland Over The Last Millenium (2015)
    Springer
    In:  EPIC3Towards an Interdisciplinary Approach in Earth System Science, Springer Earth System Sciences, Heidelberg, Springer, 9 p., pp. 197-205, ISBN: 978-3-319-13864-0
    Details
    Publication Date: 2016-11-14
    Description: Knowledge of snow accumulation rates of the large polar ice sheets and their variability over time is crucial for mass budget studies and sea level predictions. Here we present mean long-term snow accumulation rates of 12 shallow ice cores drilled by the North Greenland traverse in the northern part of Greenland. The ice core records cover the last 500 to 1000 years. We find a trend of decreasing accumulation rate from the southwest (~180 mmWE/a) to northeast (~95 mmWE/a). Ice divide sites show higher accumulation rates but also higher variability (up to 20%) than sites off the ice divides (less than 10%). Unlike a recent modeling study our results indicate no change in the accumulation in the north of Greenland during the last 400 years
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  • 176
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    A stability-dependent parametrization of transfer coefficients for momentum and heat over polar sea ice to be used in climate models (2015)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Atmospheres, Wiley, 120, pp. 1-30, ISSN: 0148-0227
    Details
    Publication Date: 2017-10-17
    Description: The interaction between sea ice and atmosphere depends strongly on the near-surface transfer coefficients for momentum and heat. A parametrization of these coefficients is developed on the basis of an existing parametrization of drag coefficients for neutral stratification that accounts for form drag caused by the edges of ice floes and melt ponds. This scheme is extended to better account for the dependence of surface wind on limiting cases of high and low ice concentration and to include near-surface stability effects over open water and ice on form drag. The stability correction is formulated on the basis of stability functions from Monin-Obukhov similarity theory and also using the Louis concept with stability functions depending on the bulk Richardson numbers. Furthermore, a parametrization is proposed that includes the effect of edge-related turbulence also on heat transfer coefficients. The parametrizations are available in different levels of complexity. The lowest level only needs sea ice concentration and surface temperature as input, while the more complex level needs additional sea ice characteristics. An important property of our parametrization is that form drag caused by ice edges depends on the stability over both ice and water which is in contrast to the skin drag over ice. Results of the parametrization show that stability has a large impact on form drag and, thereby, determines the value of sea ice concentration for which the transfer coefficients reach their maxima. Depending on the stratification, these maxima can occur anywhere between ice concentrations of 20 and 80%.
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  • 177
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    Bivalve Shells—Unique High-Resolution Archives of the Environmental Past (2015)
    Springer
    In:  EPIC3Towards an Interdisciplinary Approach in Earth System Science, (Springer Earth System Sciences), Heidelberg [u.a.], Springer, 251 p., pp. 173-182, ISBN: 978-3-319-13864-0
    Details
    Publication Date: 2015-02-11
    Description: Understanding the climate of the past is essential for anticipating future climate change. Palaeoclimatic archives are the key to the past, but few marine archives (including tropical corals) combine long recording times (decades to centuries) with high temporal resolution (decadal to intra-annual). In temperate and polar regions carbonate shells can perform the equivalent function as a proxy archive as corals do in the tropics. The bivalve Arctica islandica is a particularly unique bio-archive owing to its wide distribution throughout the North Atlantic and its extreme longevity (up to 500 years). This paper exemplifies how information at intra-annual and decadal scales is derived from A. islandica shells and combined into a detailed picture of past conditions. Oxygen isotope analysis (δ18O) provides information on the intra-annual temperature cycle while frequency analysis of shell growth records identifies decadal variability such as a distinct 5-year signal, which might be linked to the North Atlantic Oscillation.
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    A Sediment Budget for the Transkei Basin, Southwest Indian Ocean (2015)
    Springer
    In:  EPIC3Marine Geophysical Reseach, Springer, 36, pp. 281-291
    Details
    Publication Date: 2015-11-06
    Description: Deep sea sediment budgets can be used to constrain erosion rates in the neighboring continents from which the material was derived. Here we construct a sediment budget for the Transkei Basin, offshore South Africa using an existing seismic reflection survey and dated by correlation of seismic attributes to dated sections in nearby basins. Backstripping of the sections reveals that sediment accumulation rates fell from 110 to 11 Ma, with a possible period of rapid accumulation from 36 to 34 Ma that may be driven by strengthening of the Antarctic Bottom Water (AABW). The long term trend is linked to erosional degradation of the onshore continental escarpment, formed as a consequence of continental break-up. No change is noted at 30 Ma, coincident with proposed uplift of southern Africa driven by plume activity. The basin shows a significant increase in sediment accumulation after 11 Ma, which we interpret to reflect strengthening and rerouting of the AABW from the south into Transkei Basin, as a far field effect of the start of closure of the Indonesian Throughflow.
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  • 179
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    Pushing the boundaries: Glacial/interglacial variability of intermediate and deep waters in the southwest Pacific over the last 350,000 years (2015)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 30(2), pp. 23-38, ISSN: 0883-8305
    Details
    Publication Date: 2018-08-10
    Description: Glacial/interglacial changes in Southern Ocean’s air-sea gas exchange have been considered as important mechanisms contributing to the glacial/interglacial variability in atmospheric CO2. Hence, understanding past variability in Southern Ocean intermediate to deep water chemistry and circulation is fundamental to constrain the role of these processes on modulating glacial/interglacial changes in the global carbon cycle. Our study focused on the glacial/interglacial variability in the vertical extent of southwest Pacific Antarctic Intermediate Water (AAIW). We compared carbon and oxygen isotope records from epibenthic foraminifera of sediment cores bathed in modern AAIW and Upper Circumpolar Deep Water (UCDW; 943–2066 m water depth) to monitor changes in water mass circulation spanning the past 350,000 years. We propose that pronounced freshwater input by melting sea ice into the glacial AAIW significantly hampered the downward expansion of southwest Pacific AAIW, consistent with climate model results for the Last Glacial Maximum. This process led to a pronounced upward displacement of the AAIW-UCDW interface during colder climate conditions and therefore to an expansion of the glacial carbon pool.
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  • 180
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    Regionally coupled atmosphere‐ocean‐ sea ice‐marine biogeochemistry model ROM: 1. Description and validation. (2015)
    Wiley
    In:  EPIC3Journal of Advances in Modeling Earth Systems, Wiley, ISSN: 1942-2466
    Details
    Publication Date: 2015-02-17
    Description: The general circulation models used to simulate global climate typically feature resolution too coarse to reproduce many smaller scale processes, which are crucial to determining the regional responses to climate change. A novel approach to downscale climate change scenarios is presented which includes the interactions between the North Atlantic Ocean and the European shelves as well as their impact on the North Atlantic and European climate. The goal of this paper is to introduce the global ocean – regional atmosphere coupling concept and to show the potential benefits of this model system to simulate present day climate. A global ocean – sea ice – marine biogeochemistry model (MPIOM/HAMOCC) with regionally high horizontal resolution is coupled to an atmospheric regional model (REMO) and global terrestrial hydrology model (HD) via the OASIS coupler. Moreover, results obtained with ROM using NCEP/NCAR reanalysis and ECHAM5/MPIOM CMIP3 historical simulations as boundary conditions are presented and discussed for the North Atlantic and North European region. The validation of all the model components, i.e. ocean, atmosphere, terrestrial hydrology and ocean biogeochemistry is performed and discussed. The careful and detailed validation of ROM provides evidence that the proposed model system improves the simulation of many aspects of the regional climate, remarkably the ocean, even though some biases persist in other model components, thus leaving potential for future improvement. We conclude that ROM is a powerful tool to estimate possible impacts of climate change on the regional scale.
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    Sources of new nitrogen in the Indian Ocean (2015)
    Wiley
    In:  EPIC3Global Biogeochemical Cycles, Wiley, 29, ISSN: 0886-6236
    Details
    Publication Date: 2019-08-19
    Description: Quantifying the different sources of nitrogen (N) within the N cycle is crucial to gain insights in oceanic phytoplankton production. To understand the controls of primary productivity and the associated capture of CO2 through photosynthesis in the southeastern Indian Ocean, we compiled the physical and biogeochemical data from four voyages conducted in 2010, 2011, 2012, and 2013. Overall, higher NH4 assimilation rates (~530 μmolm-2 h-1) relative to NO3 assimilation rates (~375 μmolm!2 h!1) suggest that the assimilation dynamics of C are primarily regulated by microbial regeneration in our region. N2 fixation rates did not decline when other source of dissolved inorganic nitrogen were available, although the assimilation of N2 is a highly energetic process. Our data showed that the diazotrophic community assimilated ~2 nmol N L!1 h!1 at relative elevated NH4 assimilation rates ~12 nmol L-1 h-1 and NO3 assimilation rates ~6 nmol L!1 h!1. The small diffusive deep water NO3 fluxes could not support the measured NO3 assimilation rates and consequently point toward another source of dissolved inorganic NO3. Highest NO2! values coincided consistently with shallow lower dissolved O2 layers (100–200 m; 100–180 μmol L-1). These results suggest that nitrification above the pycnocline could be a significant component of the N cycle in the eastern Indian Ocean. In our analysis we provide a conceptual understanding of how NO3 in the photic zone could be derived from new N through N2 fixation. We conclude with the hypothesis that N injected through N2 fixation can be recycled within the photic zone as NH4 and sequentially oxidized to NO2 and NO3 in shallow lower dissolved oxygen layers.
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  • 182
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    Impacts of Arctic sea-ice and continental snow-cover changes on atmospheric winter teleconnections (2015)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2019-07-16
    Description: Extreme winters in Northern Hemisphere mid-latitudes in recent years have been connected to declining Arctic sea ice and continental snow-cover changes in autumn following modified planetary waves in the coupled troposphere-stratosphere system. Through analyses of reanalysis data and model simulations with a state-of-the-art atmospheric general circulation model we investigate the mechanisms between Arctic Ocean sea ice and Northern Hemisphere land snow-cover changes in autumn and atmospheric teleconnections in the following winter. The observed negative Arctic Oscillation in response to sea-ice cover changes is too weakly reproduced by the model. The planetary wave train structures over the Pacific and North America region are well simulated. The strengthening and westward shift of the Siberian high pressure system in response to sea-ice and snow-cover changes is underestimated compared to ERA-Interim data due to deficits in the simulated changes in planetary wave propagation characteristics.
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  • 183
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    Evaluation of Eemian and Holocene Climate Trends: Combining Marine Archives with Climate Modelling (2015)
    Springer
    In:  EPIC3Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC), SpringerBriefs in Earth System Sciences, Germany, Springer, 5 p., pp. 31-35, ISBN: 978-3-319-00693-2
    Details
    Publication Date: 2015-06-05
    Description: In an attempt to assess trends of Holocene sea-surface temperature (SST), two proxies have been compiled and analyzed in light of model simulations. The data reveal contrasting SST trends, depending upon the proxy used to derive Holocene SST history. To reconcile these mismatches between proxies in the estimated Holocene SST trends, it has been proposed that the Holocene evolution of orbitally-driven seasonality of the incoming radiation is the first-order driving mechanism of the observed SST trends. Such hypothesis has been further tested in numerical models of the Earth system with important implications for SST signals ultimately recorded by marine sediment cores. The analysis of model results and alkenone proxy data for the Holocene indicate a similar pattern in temperature change, but the simulated SST trends underestimate the proxy-based SST trends by a factor of two to five. SST trends based on Mg/Ca show no correspondence with model results. We explore whether the consideration of different growing seasons and depth habitats of the planktonic organisms used for temperature reconstruction could lead to a better agreement of model results with alkenone data on a regional scale. We found that invoking shifts in the living season and habitat depth can remove some of the model–data discrepancies in SST trends. Our results indicate that modeled and reconstructed temperature trends are to a large degree only qualitatively comparable, thus providing at present a challenge for the interpretation of proxy data as well as the model sensitivity to orbital forcing.
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    Basin evolution and palaeoenvironmental variability of the thermokarst lake El’gene-Kyuele, Arctic Siberia (2015)
    Wiley
    In:  EPIC3Boreas, Wiley, 44, pp. 216-229, ISSN: 0300-9483
    Details
    Publication Date: 2016-11-23
    Description: Thermokarst lakes are a widespread feature of the Arctic tundra, in which highly dynamic processes are closely connected with current and past climate changes. We investigated late Quaternary sediment dynamics, basin and shoreline evolution, and environmental interrelations of Lake El’gene-Kyuele in the NE Siberian Arctic (latitude 71°17′N, longitude 125°34′E). The water-body displays thaw-lake characteristics cutting into both Pleistocene Ice Complex and Holocene alas sediments. Our methods are based on grain size distribution, mineralogical composition, TOC/N ratio, stable carbon isotopes and the analysis of plant macrofossils from a 3.5-m sediment profile at the modern eastern lake shore. Our results show two main sources for sediments in the lake basin: terrigenous diamicton supplied from thermokarst slopes and the lake shore, and lacustrine detritus that has mainly settled in the deep lake basin. The lake and its adjacent thermokarst basin rapidly expanded during the early Holocene. This climatically warmer than today period was characterized by forest or forest tundra vegetation composed of larches, birch trees and shrubs. Woodlands of both the HTM and the Late Pleistocene were affected by fire, which potentially triggered the initiation of thermokarst processes resulting later in lake formation and expansion. The maximum lake depth at the study site and the lowest limnic bioproductivity occurred during the longest time interval of ∼7 ka starting in the Holocene Thermal Maximum and lasting throughout the progressively cooler Neoglacial, whereas partial drainage and an extensive shift of the lake shoreline occurred ∼0.9 cal. ka BP. Correspondingly, this study discusses different climatic and environmental drivers for the dynamics of a thermokarst basin.
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    Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome (2017)
    Springer
    In:  EPIC3Polar Biology, Springer, 40(11), pp. 2265-2278, ISSN: 0722-4060
    Details
    Publication Date: 2019-08-15
    Description: Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6–7% over the current levels with a 1 °C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems.
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    Tectonic Reconstructions of the Southernmost Andes and the Scotia Sea During the Opening of the Drake Passage (2016)
    Springer
    In:  EPIC3Geodynamic Evolution of the Southernmost Andes Connections with the Scotia Arc, Springer Earth System Sciences, Springer, pp. 75-108, ISBN: 978-3-319-39725-2
    Details
    Publication Date: 2019-07-17
    Description: Study of the tectonic development of the Scotia Sea region started with basic lithological and structural studies of outcrop geology in Tierra del Fuego and the Antarctic Peninsula. To nineteenth- and early twentieth-century geologists, the results of these studies suggested the presence of a submerged orocline running around the margins of the Scotia Sea. Subsequent increases in detailed knowledge about the fragmentary outcrop geology from islands distributed around the margins of the Scotia Sea, and later their interpretation in the light of the plate tectonic paradigm led to large modifications in the hypothesis such that by the present day the concept of oroclinal bending in the region persists only in vestigial form. Of the early comparative lithostratigraphic work in the region, only the likenesses between Jurassic–Cretaceous basin floor and fill sequences in South Georgia and Tierra del Fuego are regarded as strong enough to be useful in plate kinematic reconstruction by permitting the interpretation of those regions’ contiguity in mid-Mesozoic times. Marine and satellite geophysical data sets reveal features of the remaining, submerged, 98 % of the Scotia Sea region between the outcrops. These data enable a more detailed and quantitative approach to the region’s plate kinematics. In contrast to long-used interpretations of the outcrop geology, these data do not prescribe the proximity of South Georgia to Tierra del Fuego in any past period. It is, however, possible to reinterpret the geology of those two regions in terms of the plate kinematic history that the seafloor has preserved.
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    Calibration of the Carbon Isotope Composition (δ13 C) of Benthic Foraminifera (2017)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 32(6), pp. 512-530, ISSN: 0883-8305
    Details
    Publication Date: 2017-07-21
    Repository Name: EPIC Alfred Wegener Institut
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    Vertical thermodynamic structure of the troposphere during the Norwegian young sea ICE expedition (2017)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Atmospheres, Wiley, ISSN: 0148-0227
    Details
    Publication Date: 2020-03-05
    Description: The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and boundary layer characteristics. We provide statistics of temperature inversion characteristics, static stability, and boundary layer extent. During winter, when radiative cooling is most effective, we find the strongest impact of synoptic cyclones. Changes to thermodynamic characteristics of the boundary layer are associated with transitions between the radiatively “clear” and “opaque” atmospheric states. In spring, radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. Further, we compare the N-ICE2015 static stability distributions to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Ålesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. For Ny-Ålesund, we observe similar characteristics above 1000 m, while the topography and ice-free fjord surrounding Ny-Ålesund generate great differences below. The long-term radiosonde record (1993–2014) from Ny-Ålesund indicates that during the N-ICE2015 spring period, temperatures were close to the climatological mean, while the lowest 3000 m were 1–3∘C warmer than the climatology during winter.
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    Geothermal heat flux in the Amundsen Sea sector of West Antarctica: New insights from temperature measurements, depth to the bottom of the magnetic source estimation, and thermal modeling (2017)
    Wiley
    In:  EPIC3Geochemistry Geophysics Geosystems, Wiley, 18, pp. 2657-2672, ISSN: 1525-2027
    Details
    Publication Date: 2019-07-17
    Description: Focused research on the Pine Island and Thwaites glaciers, which drain the West Antarctic Ice Shelf (WAIS) into the Amundsen Sea Embayment (ASE), revealed strong signs of instability in recent decades that result from variety of reasons, such as inflow of warmer ocean currents and reverse bedrock topogra- phy, and has been established as the Marine Ice Sheet Instability hypothesis. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Due to a complex tectonic and magmatic history of West Antarctica, the region is suspected to exhibit strong heterogeneous geothermal heat flux variations. We present an approach to investigate ranges of realistic heat fluxes in the ASE by different methods, discuss direct observations, and 3-D numerical models that incorporate boundary conditions derived from various geophysical studies, including our new Depth to the Bottom of the Magnetic Source (DBMS) estimates. Our in situ temperature measurements at 26 sites in the ASE more than triples the number of direct GHF observations in West Antarctica. We demonstrate by our numerical 3-D models that GHF spatially varies from 68 up to 110 mW m-2.
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    Social recognition in amphipods: An overview (2015)
    Springer
    In:  EPIC3Social recognition in invertebrates - The knowns and the unknowns, Springer, 16 p., pp. 85-100, ISBN: 978-3-319-17599-7
    Details
    Publication Date: 2015-06-02
    Repository Name: EPIC Alfred Wegener Institut
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  • 191
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    Pattern of cryospheric seismic events observed at Ekström ice shelf, Antarctica (2015)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 42, ISSN: 0094-8276
    Details
    Publication Date: 2019-07-17
    Description: Mobility of glaciers such as rapid retreat or disintegration of large ice volumes produces a large variety of different seismic signals. Thus, evaluating cryospheric seismic events (e.g. changes of their occurrence in space and time)allows to monitor glacier dynamics. We analyze a one year data span recorded at the Neumayer seismic network in Antarctica. Events are automatically recognized using hidden Markov models. In this study we focused on a specifc event type occurring close to the grounding line of the Ekström ice shelf. Observed waveform characteristics are consistent with an initial fracturing followed by the resonance of a water filled cavity resulting in a so-called hybrid event. The number of events detected strongly correlates with dominant tide periods. We assume the cracking to be driven by existing glacier stresses through bending. Voids are then filled by sea water, exciting the observed resonance. In agreement with this model, events occur almost exclusively during rising tides where cavities are opened at the bottom of the glacier, i.e. at the sea/ice interface.
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  • 192
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    CO2-Wirkung auf Meerestiere (2017)
    Springer
    In:  EPIC3Faszination Meeresforschung, Ein ökologisches Lesebuch, Faszination Meeresforschung, Ein ökologisches Lesebuch, Germany, Springer, 8 p., pp. 365-372, ISBN: 978-3-662-49713-5
    Details
    Publication Date: 2017-06-06
    Description: Der menschengemachte CO 2-Anstieg und die dadurch verursachte Ozeanversauerung wirken auf alle Meeresorganismen. Bei Tieren kann die Sensitivität gegenüber erhöhten CO 2-Werten sehr unterschiedlich ausfallen und begründet sich vermutlich in der Fähigkeit zur extrazellulären pH-Regulation. Die beobachteten Reaktionen gegenüber Ozeanversauerung reichen von Verhaltensänderungen bei Fischen und verlängerter Entwicklungsdauer bei Krebsen bis hin zur Wachstumsabnahme bei Muscheln und reduzierter Kalkbildung bei Korallen.
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  • 193
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    Sea-ice thickness from field measurements in the northwestern Barents Sea (2017)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 122(2), pp. 1497-1512, ISSN: 0148-0227
    Details
    Publication Date: 2017-10-10
    Description: The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter-time sea-ice area in the Arctic, at -23 +/- 4% per decade. Sea-ice thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter-borne electromagnetic (HEM) ice thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to ice thickness calculated from ice draft measured by ULS deployed between 1994 and 1996. These data show that ice thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long-range advection. In a year with a large inflow of sea-ice from the Arctic Basin, the Barents Sea ice cover is dominated by thick multiyear ice; as was the case in 2003 and 1995. In a year with an ice cover that was mainly grown in situ, the ice will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in ice thickness. In 2003 the dominant ice class was more than 2 years old; and modal sea-ice thickness varied regionally from 0.6 to 1.4 m, with the thinner ice being either first-year ice, or multiyear ice which had come into contact with warm Atlantic water. In 2014 the ice cover was predominantly locally grown ice less than 1 month old (regional modes of 0.5–0.8 m). These two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere.
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    The development of permafrost bacterial communities under submarine conditions (2017)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Biogeosciences, Wiley, 122, pp. 1689-1704, ISSN: 0148-0227
    Details
    Publication Date: 2017-10-24
    Repository Name: EPIC Alfred Wegener Institut
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    Antarctic pack ice algal distribution: Floe-scale spatial variability and predictability from physical parameters (2017)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2017-09-20
    Description: Antarctic pack ice serves as habitat for microalgae which contribute to Southern Ocean primary production and serve as important food source for pelagic herbivores. Ice algal biomass is highly patchy and remains severely undersampled by classical methods such as spatially restricted ice coring surveys. Here we provide an unprecedented view of ice algal biomass distribution, mapped (as chlorophyll a) in a 100 m by 100 m area of a Weddell Sea pack ice floe, using under-ice irradiance measurements taken with an instrumented remotely operated vehicle. We identified significant correlations (p 〈 0.001) between algal biomass and concomitant in situ surface measurements of snow depth, ice thickness, and estimated sea ice freeboard levels using a statistical model. The model’s explanatory power (r2 = 0.30) indicates that these parameters alone may provide a first basis for spatial prediction of ice algal biomass, but parameterization of additional determinants is needed to inform more robust upscaling efforts.
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    Dynamical reconstruction of the global ocean state during the Last Glacial Maximum (2017)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 32, ISSN: 0883-8305
    Details
    Publication Date: 2017-04-25
    Description: The global ocean state for the modern age and for the Last Glacial Maximum (LGM) was dynamically reconstructed with a sophisticated data assimilation technique. A substantial amount of data including global seawater temperature, salinity (only for the modern estimate), and the isotopic composition of oxygen and carbon (only in the Atlantic for the LGM) were integrated into an ocean general circulation model with the help of the adjoint method, thereby the model was optimized to reconstruct plausible continuous fields of tracers, overturning circulation and water mass distribution. The adjoint-based LGM state estimation of this study represents the state of the art in terms of the length of forward model runs, the number of observations assimilated, and the model domain. Compared to the modern state, the reconstructed continuous sea-surface temperature field for the LGM shows a global-mean cooling of 2.2 K, and the reconstructed LGM ocean has a more vigorous Atlantic meridional overturning circulation, shallower North Atlantic Deep Water (NADW) equivalent, stronger stratification, and more saline deep water.
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    Springtime dynamics, productivity and activity of prokaryotes in two Arctic fjords (2016)
    Springer
    In:  EPIC3Polar Biology, Springer, 39(10), pp. 1749-1763, ISSN: 0722-4060
    Details
    Publication Date: 2017-06-05
    Description: In the Kongsfjorden–Krossfjorden system (Spitsbergen), increasing temperatures enhance glacier melting and concomitant intrusion of freshwater. These altered conditions affect the timing, intensity, and composition of the phytoplankton spring bloom in Kongsfjorden; yet, the effects on prokaryotes (bacteria and archaea) are not well understood. The aim of this study was to examine springtime prokaryote communities in both fjords as a function of hydrographic and phytoplankton variability. Prokaryote community composition was studied in two consecutive years by molecular fingerprinting of the 16S rRNA gene. In addition, we measured bacterial abundance, productivity (3H-Leucine uptake), and single-cell activity using catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography. Differences in bacterial and archaeal communities were found etween Kongsfjorden and Krossfjorden. Furthermore, an increase in productivity, abundance, and proportion of active bacterial cells was observed during the course of spring. Bacteroidetes were the most abundant bacterial group among the assessed taxa in both Kongsfjorden and Krossfjorden. Multivariate analysis of the microbial community fingerprints revealed a strong temporal shaping of both the bacterial and archaeal communities in addition to a spatial separation between the two fjords. A significant part of the observed bacterial variation could be explained by cyanobacterial biomass, as deduced from pigment analysis, and by phosphate concentration. Archaea were mainly controlled by abiotic factors. We speculate that the bacterial response to hydrographic changes and glacier meltwater is mediated through shifts in phytoplankton abundance and composition, whereas archaea are directly influenced by abiotic environmental variables.
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    Warm water pathways toward Nioghalvfjerdsfjorden Glacier, Northeast Greenland (2017)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 122(5), pp. 4004-4020, ISSN: 0148-0227
    Details
    Publication Date: 2018-01-02
    Description: Nioghalvfjerdsfjorden Glacier (79NG) is the largest of three marine-terminating outlet glaciers draining the Northeast Greenland Ice Stream. To understand how Atlantic waters supply waters in the cavity beneath the floating 79NG, we analyze historic and recent bathymetric, hydrographic, and velocity observations obtained on the Northeast Greenland continental shelf. The bathymetry is characterized by a trough system, consisting of the Westwind Trough and the Norske Trough in the northern and southern part of the continental shelf, respectively. Atlantic waters recirculating in Fram Strait cross the shelf break and enter the trough system at its southeastern inlet toward the inner shelf. Warm Atlantic Intermediate Water (AIW) present below 200 m in the Norske Trough shows large contributions of the recirculating Atlantic water. We found that the bathymetry is sufficiently deep to provide a direct subsurface pathway for warm AIW between the shelf break and the 79NG cavity via the Norske Trough. Likewise, based on the hydrographic data, we show that the Norske Trough supplies AIW warmer than 1°C to the 79NG, which is not present in the Westwind Trough. Our moored and lowered velocity measurements indicate that a boundary current carries warm AIW along the northeastern slope of Norske Trough toward the 79NG. We suggest that anomalies in Atlantic water temperatures in Fram Strait could reach 79NG within less than 1.5 years, thereby modifying the glacier's basal melt rates.
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    Synchronous and proportional deglacial changes in Atlantic meridional overturning and northeast Brazilian precipitation (2017)
    Wiley
    In:  EPIC3Paleoceanography, Wiley, 32(6), pp. 622-633, ISSN: 0883-8305
    Details
    Publication Date: 2018-08-10
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    Impact of snow accumulation on CryoSat-2 range retrievals over Arctic sea ice: An observational approach with buoy data (2015)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2019-07-17
    Description: Radar altimetry measurements of the current satellite mission CryoSat-2 show an increase of Arctic sea ice thickness in autumn 2013, compared to previous years but also related to March 2013. Such an increase over the melting season seems unlikely and needs to be investigated. Recent studies show that the influence of the snow cover is not negligible and can highly affect the CryoSat-2 range retrievals if it is assumed that the main scattering horizon is given by the snow-ice interface. Our analysis of Arctic ice mass balance buoy records and coincident CryoSat-2 data between 2012 and 2014 adds observational evidence to these findings. Linear trends of snow and ice freeboard measurements from buoys and nearby CryoSat-2 freeboard retrievals are calculated during accumulation events. We find a positive correlation between buoy snow freeboard and CryoSat-2 freeboard estimates, revealing that early snow accumulation might have caused a bias in CryoSat-2 sea ice thickness in autumn 2013.
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