ALBERT

Description: The sensitive high-resolution ion microprobe (SHRIMP) developed at the Australian National University (ANU) was the first of the high-resolution ion microprobes. The impact of this instrument on geochronological research over the last twenty years has been immense. This is particularly so for lunar geochronology where it has opened up avenues of research that were not possible using conventional TIMS techniques. The great advantage of SHRIMP is that it provides a means for determining precise U–Pb isotopic ratios on selected micron-size areas on polished grains of zircon and other U-bearing minerals. One of the first projects undertaken on the newly invented SHRIMP I was an investigation of U–Pb ages of lunar zircon. Using SHRIMP, multiple analyses could be made on areas of individual zircons to test the stability of U–Pb systems in shocked grains. Also, by analysing grains “in situ”, textural relationships between the analysed zircon and the components of the sample breccia could be used in the interpretation of the SHRIMP data. As a result of this research it was realised that most lunar zircons have ages up to 500Ma older than the Imbrium and Serenitatis impacts at ca. 3.9 Ga, demonstrating that the zircons have not been affected by the these impact events although heating and shock effects have profoundly disturbed other dating systems. This has opened the way for research into the early lunar magmatic and bombardment record. For example, recent SHRIMP results have revealed profound differences in the ages of zircons from breccias from the Apollo 14 and Apollo 17 sample sites, raising new questions about the evolution of lunar magmatism. Also, multiple SHRIMP analyses on complex lunar zircons have shown that these grains can record U–Pb disturbance by later impact events. SHRIMP U–Pb age determinations on phosphates in lunar meteorites has identified lunar events not recognised in samples from the Apollo program. SHRIMP-based research on lunar materials is ongoing and, in combination with other chemical and structural evidence, continues to stimulate new ideas on the early evolution of the Moon.

Description: Fresh volcanic glasses from the extrusive section of the Troodos Ophiolite in Akaki Canyon are tholeiitic and basaltic to dacitic in composition. Compared to normal MORB they have extremely low fractionation corrected Na8, Fe8 and Ti8 and are enriched in fluid-mobile trace elements, including U, Ba, Rb, Sr and Pb, relative to non-fluid mobile elements of similar incompatibility. Trace element compositions of Akaki lavas define an array extending between ‘back-arc lava’-like compositions, and the field defined by Troodos boninites from the upper part of the lava sequence. Troodos lavas were derived from a mantle source that underwent early melt depletion, and later enrichment by both fluids and small degree melts. These processes can explain the unusual negative correlation of Pb/Ce with Zr/Nb and Ba/Nb in Troodos extrusives. Although some Troodos lavas are similar in composition to lavas from back-arc spreading centres, the boninites from the upper parts of the lava pile do not appear to have exact compositional equivalents among lavas from fore-arcs, back-arcs or other tectonic settings where similar rocktypes have been recovered. We suggest that the geochemical evolution inferred for the mantle source of Troodos lavas, together with geological evidence is most consistent with an origin for the Troodos Ophiolite at a spreading centre close to a ridge–trench–trench, or ridge–trench–transform triple junction, where highly depleted, subduction-modified, fluid-enriched mantle wedge material was able to upwell and decompress to shallow depths in a ‘fore-arc’ location. In such a tectonic setting, arc volcanism is captured by the spreading centre, explaining the lack of evidence for subaerial arc magmatism in Troodos. Rapid lateral migration of the triple junction could account for the similar ages of other Tethyan supra-subduction zone ophiolites.

Description: Barnacles of the superfamily Coronuloidea are obligate epibionts of various marine mammals, marine reptiles and large crustaceans. We used five molecular markers: 12S rDNA, 16S rDNA, 18S rDNA, 28S rDNA and Histone 3 to infer phylogenetic relationships among sixteen coronuloids, representing most of the recent genera of barnacles of this superfamily. Our analyses confirm the monophyly of Coronuloidea and that this superfamily and Tetraclitoidea are sister groups. The six-plated Austrobalanus clusters with these two superfamilies. Based on BEAST and ML trees, Austrobalanus is basal and sister to the Coronuloidea, but the NJ tree places Austrobalanus within the Tetraclitoidae, and in the MP tree it is sister to both Coronuloidea and Tetraclitoidae. Hence the position of Austrobalanus remains unresolved. Within the Coronuloidea we identified four clades. Chelonibia occupies a basal position within the Coronuloidea which is in agreement with previous studies. The grouping of the other clades does not conform to previous studies. Divergence time analyses show that some of the time estimates are congruent with the fossil record while some others are older, suggesting the possibility of gaps in the fossil record.

Description: Several lines of evidence have previously been used to suggest that ice retreat after the last glacial maximum (LGM) resulted in regionally-increased levels of volcanic activity. It has been proposed that this increase in volcanism was globally significant, forming a substantial component of the post-glacial rise in atmospheric CO2, and thereby contributing to climatic warming. However, as yet there has been no detailed investigation of activity in glaciated volcanic arcs following the LGM. Arc volcanism accounts for 90% of present-day subaerial volcanic eruptions. It is therefore important to constrain the impact of deglaciation on arc volcanoes, to understand fully the nature and magnitude of global-scale relationships between volcanism and glaciation. The first part of this paper examines the post-glacial explosive eruption history of the Andean southern volcanic zone (SVZ), a typical arc system, with additional data from the Kamchatka and Cascade arcs. In all cases, eruption rates in the early post-glacial period do not exceed those at later times at a statistically significant level. In part, the recognition and quantification of what may be small (i.e. less than a factor of two) increases in eruption rate is hindered by the size of our datasets. These datasets are limited to eruptions larger than 0.1 km3, because deviations from power-law magnitude–frequency relationships indicate strong relative under-sampling at smaller eruption volumes. In the southern SVZ, where ice unloading was greatest, eruption frequency in the early post-glacial period is approximately twice that of the mid post-glacial period (although frequency increases again in the late post-glacial). A comparable pattern occurs in Kamchatka, but is not observed in the Cascade arc. The early post-glacial period also coincides with a small number of very large explosive eruptions from the most active volcanoes in the southern and central SVZ, consistent with enhanced ponding of magma during glaciation and release upon deglaciation. In comparison to non-arc settings, evidence of post-glacial increases in rates of arc volcanism is weak, and there is no need to invoke significantly increased melt production upon ice unloading, as occurred in areas such as Iceland. Non-arc volcanoes may therefore account for a relatively higher proportion of global volcanic emissions in the early post-glacial period than is suggested by the relative contributions of arc and non-arc settings at the present day. The second part of this paper critically examines global eruption records, in an effort to constrain global-scale changes in volcanic output since the LGM. Accurate interpretation of these records relies on correcting both temporal and spatial variability in eruption recording. In particular, very low recording rates, which also vary spatially by over two orders of magnitude, prevent precise, and possibly even accurate, quantitative analysis. For example, if we assume record completeness for the past century, the number of known eruptions (volcanic explosivity index ≥ 2) from some low-latitude regions, such as Indonesia, is approximately 1 in 20,000 (0.005%) for the period 5–20 ka. There is a need for more regional-scale studies of past volcanism in such regions, where current data are extremely sparse. We attempt to correct for recording biases, and suggest a maximum two-fold (but potentially much less) increase in global eruption rates, relative to the present day, between 13 and 7 ka. Although volcanism may have been an important source of CO2 in the early Holocene, it is unlikely to have been a dominant control on changes in atmospheric CO2 after the LGM.

Description: Abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical Atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected. As expected from previous work in the tropics, all dominant tropical species occur in greatest abundance within the photic zone. Many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration, while a few algal symbiont-bearing species occur in greatest abundance in the mixed layer. The δ18O measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by Ravelo et al. [1990]. Comparison between the measured δ18O values of planktonic foraminifera with the predicted δ18O profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year. Species which calcify below the photic zone have only trace relative abundances. Finally, it appears that the total range of δ18O values of the dominant species approximates the predicted annual δ18O of calcite range in the upper 80 m of the water column.

Description: In virtually every assessment of responses to large-scale crises and disasters, coordination is identified as a critical failure factor. After the crisis, official committees and political opponents often characterize the early phases of the response as a ‘failure to coordinate.’ Not surprisingly, improved coordination quickly emerges as the prescribed solution. Coordination, then, is apparently both the problem and the solution. But the proposed solutions rarely solve the problem: coordination continues to mar most crises and disasters. In the absence of a shared body of knowledge on coordination, it is hard to formulate a normative framework that allows for systematic assessment of coordination in times of crisis. As coordination is widely perceived as an important function of crisis and disaster management, this absence undermines a fair and balanced assessment of crisis management performance. This paper seeks to address that void. We aim to develop a framework that explains both the failure and success of crisis coordination. We do this by exploring the relevant literature, reformulating what coordination is and distilling from research the factors that cause failure and success.

Description: The purine alkaloid caffeine is a major component of many beverages such as coffee and tea. Caffeine and its metabolites theobromine and xanthine have been shown to have antioxidant properties. Caffeine can also act as adenosine-receptor antagonist. Although it has been shown that adenosine and antioxidants promote wound healing, the effect of caffeine on wound healing is currently unknown. To investigate the effects of caffeine on processes involved in epithelialisation, we used primary human keratinocytes, HaCaT cell line and ex vivo model of human skin. First, we tested the effects of caffeine on cell proliferation, differentiation, adhesion and migration, processes essential for normal wound epithelialisation and closure. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) proliferation assay to test the effects of seven different caffeine doses ranging from 0·1 to 5 mM. We found that caffeine restricted cell proliferation of keratinocytes in a dose-dependent manner. Furthermore, scratch wound assays performed on keratinocyte monolayers indicated dose-dependent delays in cell migration. Interestingly, adhesion and differentiation remained unaffected in monolayer cultures treated with various doses of caffeine. Using a human ex vivo wound healing model, we tested topical application of caffeine and found that it impedes epithelialisation, confirming in vitro data. We conclude that caffeine, which is known to have antioxidant properties, impedes keratinocyte proliferation and migration, suggesting that it may have an inhibitory effect on wound healing and epithelialisation. Therefore, our findings are more in support of a role for caffeine as adenosine-receptor antagonist that would negate the effect of adenosine in promoting wound healing.

Description: Geochemical cycles occurring at the interface between terrestrial and marine groundwaters, in the so-called subterranean estuary (STE), are not well understood for most elements. This is particularly true of the transition metals, many of which have particular ecological relevance as micronutrients or toxicants. To gain a first approximation of trace metal geochemistry in the mixing zone, we examined the distribution of nine dissolved metals (Fe, Mn, Mo, V, Co, Ni, Cu, Pb, and Al) through a shallow STE in Great South Bay, New York, USA. We also performed a simple kinetic and chemical separation of labile and organic-complexed metal species in the STE. Dissolved Mn showed marked subsurface enrichment (up to 755 µM at 15 cm depth) that was suggestive of diagenetic remobilization. Dissolved Fe, however, was higher by more than three orders-of-magnitude in fresh groundwater (90 µM) as compared to marine groundwater (0.02 µM), and pH-mediated removal was evident as slightly acidic fresh groundwater (pH 6.8) mixed with marine groundwater (pH ∼ 8.0). Dissolved Mo, Co, and Ni were primarily cycled with Mn, and highly elevated concentrations relative to bay surface waters (up to 300, 75, and 44 nM, respectively) were observed in the STE. High levels of dissolved Pb (up to 4250 pM) observed in the fresh groundwater were nearly quantitatively removed within the salinity mixing zone, in conjunction with marked reduction of dissolved Al. Dissolved Cu exhibited non-conservative removal throughout the STE, and was correlated with the redox potential of the porewaters. Substantial percentages (〉 15%) of organic-metal species were only observed for Cu and Ni, suggesting that these complexes were not generally very important for metal cycling in the STE. Kinetically labile species were observed for all metals examined except Cu and Pb, and represented an approximately constant proportion (between 10% and 70%) of the total dissolved pool for each metal, indicating equilibrium between labile and non-labile species throughout the mixing zone. The non-conservative behavior observed for all metals examined in this study suggests that reactions occurring in the STE are vastly important to the source/sink function of permeable sediments, and studies seeking to quantify SGD-derived trace metal fluxes must take into account biogeochemical processes occurring in the subterranean estuary.

Description: Ra isotopes are a powerful tool for quantifying the flux of submarine groundwater discharge (SGD) into the sea. Previous studies of 223Ra and 224Ra mass balances in coastal embayments have shown that the Ra balance is dominated by supply via SGD, exchange with the open ocean and radioactive decay. The current study shows that a single time series over a tidal cycle at the principal inlet to Great South Bay (NY, US) is sufficient to determine the net flux of Ra across the inlet, and also can be used to estimate the decay of short-lived Ra in the bay. Estimates of the net Ra flux obtained from a single tidal time-series by using three different approaches agree with those determined from a more time-consuming survey of Ra within the bay, and may represent a first step of estimating SGD in bays and coastal lagoons.

Description: Core PRAD 1-2, located on the western flank of the Mid-Adriatic Deep, contains a continuous sediment record extending back to upper MIS-11. The upper part of the record which spans the mid Holocene to MIS 5–4 (the last ca 105,000 years) has been investigated for tephra content. A total of 25 discrete tephra layers were discovered, only one of which was visible in the core sequence. The other 24 are not visible to the naked eye, nor were the majority detected by routine down-core scanning methods. A total of 625 geochemical measurements obtained from individual glass shards using WDS-EPMA enabled 21 of the 25 tephras to be assigned to known volcanic events emanating from the Campanian Province (Campi Flegrei, Somma-Vesuvius and Ischia Island). The results provide an independent basis for establishing an age–depth profile for the upper part of the PRAD 1-2 record. This study demonstrates that the number of non-visible tephra layers can significantly exceed the number of visible layers in some deep marine sequences. Routine testing for the presence of non-visible tephra layers can therefore prove rewarding, leading to the detection of additional isochrons for dating and correlating marine sequences, and for their synchronisation with terrestrial records.

Description: Pore water has been analyzed from sediment cores taken from three areas on the eastern flank of the Juan de Fuca Ridge as part of FlankFlux 90, a study of hydrothermal circulation through mid-ocean ridge flanks. Seismic reflection and heat flow surveys (Davis et al., 1992a) indicate that the three areas differ in sediment thickness, basement topography, abundance of outcrops, basement temperature, and fraction of heat lost by advection versus conduction. Area 1 is on 0.6 Ma crust with nearly continuous basement outcrop, area 2 is on 1.3 Ma crust over the first buried ridge parallel to the present ridge axis, and area 3 is on 3.5–3.8 Ma crust over two axis-parallel buried ridges that penetrate the sediment cover in three locations. Each area includes a hydrothermal system in which seawater flows into basement, reacts with crustal basalt, and then exits basement either through the sediment or directly into the overlying water column. As constrained by concentrations of sulfate and lithium in the pore waters, at least some seawater enters basement in all three areas without reacting fully with the overlying sediment, even where no outcrops are known nearby. Speeds of up welling of pore water through the sediment have been estimated by fitting profiles of dissolved magnesium and chlorinity, which behave conservatively in these areas, to numerical time-dependent transport models. The estimated velocities range from 〈0.1 to 7.4 cm/yr; faster flows probably occur but were not sampled. Upwelling speed correlates positively with heat flow and basement highs and negatively with sediment thickness. The correlation with heat flow differs from area 2 to area 3 along with differences in physical properties of the turbidite sediment. We have documented pore water upwelling through sediment up to 100 m thick. We estimate that upwelling continues at decreasing speeds through sediment up to 160 m thick, corresponding to a heat flow of 0.44 W/m2 in area 2 and 0.3 W/m2 in area 3. Concentrations of magnesium and chlorinity in the altered seawater upwelling from basement are uniform within each area but differ from one area to the next. Both species remain at the bottom seawater concentration in area 1, where basement is cooled to 〈10°C at the base of the sediments mainly by advection. The concentration of magnesium decreases with increasing basement temperature in areas 2 and 3 to a minimum of 2.5 mmol/kg at about 90°C in area 3. The transition from largely advective to largely conductive heat loss occurs over only 20 km between areas 1 and 2 and corresponds to a dramatic change in the composition of fluid circulating through basement, as the uppermost basement is heated from 〈10° to 40–50°C. Chlorinity of the basement fluid increases above the present-day bottom seawater concentration in areas 2 and 3 and in nearly all other mid-ocean ridge flanks studied to date, as a result of rock hydration and the higher chlorinity of bottom seawater during the last glacial period. While chlorinity generally correlates positively with uppermost basement temperature in various ridge flank hydrothermal systems, it reaches a maximum in area 2 at only 40°C, probably because alteration there occurs at a lower water/rock ratio than elsewhere. For all mid-ocean ridge flanks studied to date, the temperature at the basement interface correlates better with the fraction of heat lost by advection versus conduction and with the average thickness of the sediment cover than with crustal age.

Description: Geoengineering, especially its potentially fast and high-leverage versions, is often justified as a necessary response to possible future climate emergencies. In this article, we take the notion of ‘necessity’ in international law as a starting point in assessing how rapid, high-leverage geoengineering might be justified legally. The need to specify reliably ‘grave and imminent peril’ makes such a justification difficult because our scientific ability to predict abrupt climate change, for example, as tipping elements, is limited. The time it takes to establish scientific consensus as well as policy acceptance restricts the scope for effective forewarning and so pre-emptive justifications for geoengineering become more tempting. While recognizing that dangerous, large-scale impacts of climate change is becoming increasingly difficult to avoid, the pre-emptive, emergency frame is problematic. We suggest that arguments from emergency operate on a high level of uncertainty and tend toward hubristic attempts to shape the future, as well as tending to close down rather than open up space for deliberation. We conclude that the emergency frame is not likely to go away, that ignoring or repressing it is a dangerous response, and that more effort is required to defuse and disarm emergency rhetoric.

Description: In May 2006 high-resolution measurements using ground-penetrating radar (GPR) and magnetic gradiometer systems conducted over selected areas at the site of the Viking Age settlement and trading place Birka in central Sweden demonstrated the suitability of these methods for archaeological prospection of Scandinavian proto-urban settlements. The non-invasive geophysical surveys revealed numerous structural details of the settlement: houses, property boundaries, track-ways, buried remains of the town ramparts dating from different building periods, including a gate, were mapped with a manually operated single-channel GPR system and a four-channel magnetometer array. The combination of these two prospection methods, state-of-the-art data processing and visualization and archaeological interpretation within a geographical information system resulted in valuable new information about the UNESCOWorld Cultural Heritage Site Birka-Hovgården.We present methodology and results of this first archaeological prospection case study conducted in 2006.

Description: An examination of 311 intraplate earthquakes in the Australian plate portion of the Pacific Ocean basin reported from 1918 to 1990 reveals that only 113 events are reliably intraplate, with most of the rest relocating to active trenches and transforms. The non-random distribution of the reliably intraplate events gives insight into the tectonic stresses present. The central Tasman Sea is mostly aseismic except for a swarm of activity at the predicted site of the Tasmantid hot spot. To the north, the broad regions of the Coral Sea, South Fiji Basin and Lord Howe Rise show very little intraplate seismicity, yet the narrow Norfolk Ridge and Three Kings Rise, caught between the double convergence of the New Hebrides and Tonga subduction zones, support many more earthquakes. High levels of intraplate seismicity in the southern Tasman Sea adjacent to the Macquarie Ridge Complex (MRC) indicate that this region may be undergoing internal deformation due to the unusual nature of the Australia-Pacific plate boundary. Additional support exists in the form of intraplate focal mechanisms similar to those at the plate boundary and a set of parallel gravity rolls which are observed in recent geoid maps. Some aftershocks of the Mw = 8.2 Macquarie Ridge earthquake of 1989 occurred in a fracture zone west of the Macquarie Ridge Complex [Das, 1992], but we have found several earthquakes from as early as 1924 which relocate to this feature, suggesting that its reactivation may be more significant than previously thought. This reactivation of a fossil fracture zone may be the result of the increasing amount of oblique convergence between the Australia and Pacific plates at the Macquarie Ridge Complex, formerly a spreading center, and the stresses associated with subducting recently formed Australian ocean crust beneath the older Pacific plate.

Description: Calcium isotopes in tissues are thought to be influenced by an individual’s diet, reflecting parameters such as trophic level and dairy consumption, but this has not been carefully assessed. We report the calcium isotope ratios (δ44/42Ca) of modern and archaeological animal and human bone (n = 216). Modern sheep raised at the same location show 0.14 ± 0.08‰ higher δ44/42Ca in females than in males, which we attribute to lactation by the ewes. In the archaeological bone samples the calcium isotope ratios of the herbivorous fauna vary by location. At a single site, the archaeological fauna do not show a trophic level effect. Humans have lower δ44/42Ca than the mean site fauna by 0.22 ± 0.22‰, and the humans have a greater δ44/42Ca range than the animals. No effect of sex or age on the calcium isotope ratios was found, and intra-individual skeletal δ44/42Ca variability is negligible. We rule out dairy consumption as the main cause of the lower human δ44/42Ca, based on results from sites pre-dating animal domestication and dairy availability, and suggest instead that individual physiology and calcium intake may be important in determining bone calcium isotope ratios.

Description: The eastern Mediterranean transient (EMT) was caused by a combination of high‐salinity waters intruding into the Aegean Sea and the two particularly strong winters of 1991–1992 and 1992–1993. The approach in this chapter is to search for specific signatures in the historic hydrographic observations, which date back to 1910. To deal with the problem that up into the 1950s the data not only are of limited precision but also have gaps of about 20 years, it is advantageous to consider the fact that the evolution of the actual EMT is rather well documented over a similar time span. The chapter begins by outlining the characteristics of the current EMT. Thereafter, a selection of suitable hydrographic observations among the available historic data is provided to compare these with signatures expected from the evolution of the actual EMT.

Description: Polygonal patterned ground in polar regions of both Earth and Mars has received considerable attention. In comparison with the size, shape, and arrangement of the polygons, the diverse micro-relief and topography (termed here simply “relief”) of polygonal patterned ground have been understudied. And yet, the relief reflects important conditions and processes occurring directly below the ground surface, and it can be observed readily in the field and through remote sensing. Herein, we describe the relief characteristic of the simplest and relatively young form of patterned ground in the Dry Valleys of Antarctic. We also develop a numerical model to examine the generation of relief due to subsurface material being shouldered aside contraction cracks by incremental sand wedges growth, and to down-slope creep of loose granular material on the surface. We model the longterm subsurface deformation of ice-cemented permafrost as a non-linear viscous material. Our modeling is guided and validated using decades of field measurements of surface displacements of the permafrost and relief. This work has implications for assessing the activity of surfaces on Earth and Mars, and much larger scale potential manifestations of incremental wedging in icy material, namely the distinct paired ridges on Europa.

Description: This article presents a fundamental study on the role of particle breakage on the shear behavior of granular soils using the three-dimensional (3-D) discrete element method. The effects of particle breakage on the stress ratio, volumetric strain, plastic deformation, and shear failure behavior of dense crushable specimens undergoing plane strain shearing conditions are thoroughly investigated through a variety of micromechanical analyses and mechanism demonstrations. The simulation of a granular specimen is based on the effective modeling of realistic fracture behavior of single soil particles, which is demonstrated by the qualitative agreement between the results from platen compression simulations and those from physical laboratory tests. The simulation results show that the major effects of particle breakage include the reduction of volumetric dilation and peak stress ratio and more importantly the plastic deformation mechanisms and the shear failure modes vary as a function of soil crushability. Consistent macro- and micromechanical evidence demonstrates that shear banding and massive volumetric contraction depict the two end failure modes of a dense specimen, which is dominated by particle rearrangement–induced dilation and particle crushing–induced compression, respectively, with a more general case being the combination and competition of the two failure modes in the medium range of soil crushability and confining stress. However, it is further shown that a highly crushable specimen will eventually develop a shear band at a large strain because of the continuous decay of particle breakage.

Description: The geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins (Millungera, Galilee and Cooper basin) of the Australian Great Artesian Basin (GAB) consistently indicate the presence of fluids from multiple gas sources located in the crust (e.g. sediments, oil reservoirs, granites) as well as minor but detectable contributions of mantle/magma-derived fluids. The gases extracted from 19 water samples and analyzed for their chemical and isotopic composition exhibit amounts of CO2 up to about 340 mlSTP/LH2O marked by a δ13CTDC (Total Dissolved Carbon) ranging from − 16.9 to + 0.18‰ vs PDB, while CH4 concentrations vary from 4.4 × 10− 5 to 4.9 mlSTP/LH2O. Helium contents were between 9 and 〉 2800 times higher than equilibrium with Air Saturated Water (ASW), with a maximum value of 0.12 mlSTP/LH2O. Helium isotopic composition was in the 0.02–0.21 Ra range (Ra = air-normalized 3He/4He ratio). The three investigated basins differ from each other in terms of both chemical composition and isotopic signatures of the dissolved gases whose origin is attributed to both mantle and crustal volatiles. Mantle He is present in the west-central and hottest part of the GAB despite no evidence of recent volcanism. We found that the partial pressure of helium, significantly higher in crustal fluids than in mantle-type volatiles, enhances the crustal He signature in the dissolved gases, thus masking the original mantle contribution. Neotectonic activity involving deep lithospheric structures and magma intrusions, highlighted by recent geophysical investigations, is considered to be the drivers of mantle/magmatic volatiles towards the surface. The results, although pertaining to artesian waters from a vast area of 〉 542,000 km2, provide new constraints on volatile injection, and show that fluids' geochemistry can provide additional and independent information on the geo-tectonic settings of the Great Artesian Basin and its geothermal potential.

Description: Extraction of groundwater or hydrocarbons causes pore pressure gradients and soil deformation due to poroelastic coupling. Recent studies show that high-resolution engineering tiltmeters installed at shallow depth between 2 and 10 m resolve this deformation. Models using poroelasticity can describe the relationship between fluid extraction, pore pressure gradients and induced tilt for homogeneous and layered sedimentary half spaces. Faults intersecting a stack of sedimentary layers, for example in the Lower-Rhine-Embayment, are of fundamental impact to the groundwater flow system of an area. However, the fault’s hydromechanical effect on pump induced tilt and the pore pressure regime is still poorly investigated. We chose a comparatively simple approach to quantify anomalous pump induced tilt and pore pressure observed near a fault and close to the surface in a sedimentary subsoil. A PC-based Finite Element software is used to model poroelastic deformation, i.e. modelling vertical tilt and excess pore pressure in response to fluid extraction through a singular well. We compare numerical solutions for models with and without faults and show that a fault can modify symmetry and amplitude of the deformation field by more than a magnitude. We conclude that tilt and pore pressure measurements also at shallow depth can thus be biased by large subsurface structures like faults. Vice versa, these measurements may provide means to quantify hydromechanical effects caused by subsurface structures. However, depending on the geological setting, i.e. if pathways are established by a fault, the anomaly caused by the fault can also be small and hard to detect. Therefore, faults and geological structures like material boundaries have to be considered in poroelastic models carefully. For tilt surveys with a limited number of instruments in geologically well constrained areas these models allow the preselection of potential positions for tiltmeters where prominent field anomalies are expected

Description: Porangahau Ridge, located offshore the Wairarapa on the Hikurangi Margin, is an active ocean-continent collision region in northeastern New Zealand coastal waters. Bottom simulating reflections (BSRs) in seismic data indicate the potential for significant gas hydrate deposits across this part of the margin. Beneath Porangahau Ridge a prominent high-amplitude reflection band has been observed to extend from a deep BSR towards the seafloor. Review of the seismic data suggest that this high-amplitude band is caused by local shoaling of the base of gas hydrate stability due to advective heat flow and it may constitute the location of elevated gas hydrate concentrations. During R/V Tangaroa cruise TAN0607 in 2006 heat flow probing for measurements of vertical fluid migration, sediment coring for methane concentrations, and additional seismic profiles were obtained across the ridge. In a subsequent 2007 expedition, on R/V Sonne cruise SO191, a controlled source electromagnetic (CSEM) experiment was conducted along the same seismic, geochemical, and heat flow transect to reveal the electrical resistivity distribution. CSEM data highlight a remarkable coincidence of anomalously high resistivity along the western, landward flank of the ridge which point to locally higher gas hydrate concentration above the high amplitude reflection band. Measured sediment temperature profiles, also along the western flank, consistently show non-linear and concave geothermal gradients typical of advective heat flow. Geochemical data reveal elevated methane concentrations in surface sediments concomitant with a rapid decline in sulfate concentrations indicating elevated methane flux and oxidation of methane in conjunction with sulfate reduction at the landward ridge base. Together, these data sets suggest that the western rim of Porangahau Ridge is a tectonically driven zone of rising fluids that transport methane and cause an upward inflection of the base of gas hydrate stability and the formation of locally enriched gas hydrate above the reflective zone.

Description: The relationship of sea-level changes and short-term climatic changes with turbidite deposition is poorly documented, although the mechanisms of gravity-driven sediment transport in submarine canyons during sea-level changes have been reported from many regions. This study focuses on the activity of the Dakar Canyon off southern Senegal in response to major glacial/interglacial sea-level shifts and variability in the NW-African continental climate. The sedimentary record from the canyon allows us to determine the timing of turbidite events and, on the basis of XRF-scanning element data, we have identified the climate signal at a sub-millennial time scale from the surrounding hemipelagic sediments. Over the late Quaternary the highest frequency in turbidite activity in the Dakar Canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea-level rise. However, episodic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly, with evidence for higher dust supply over NW Africa which has fed turbidity currents. Increased aridity and enhanced wind strength in the southern Saharan–Sahelian zone may have provided a source for this dust.

Description: Vertical distributions of iron and iron binding ligands were determined in 2 size classes (dissolved 〈 0.2 μm, soluble 〈 200 kDa, e.g., ~ 0.03 μm) in the Southern Ocean. Colloidal iron and complexing capacity (〉 200 kDa–〈 0.2 μm) were inferred as the difference between the dissolved and soluble fractions. Dissolved iron and ligands exist primarily in the soluble size range in the surface waters, although iron-complexing colloids still represent a significant portion of the dissolved pool and this fraction increases markedly with depth. This work presents evidence for the colloidal nature of a significant portion (37–51% on average) of the ‘dissolved’ organic Fe pool in these oceanic waters. From the data it was not possible to discern whether iron colloids exist as discrete organic complexes and/or inorganic amorphous colloids. Iron-complexing colloids are the most saturated with iron at the thermodynamic equilibrium, whereas soluble organic ligands occur in larger excess compared to soluble iron. It suggests that the exchangeable fraction for iron uptake through dissociation of Fe complexes likely occurs in the soluble fraction, and that soluble ligands have the potential to buffer iron inputs to surface waters whereas iron colloids may aggregate and settle. Expectations based on Fe diffusion rates, distributions and the stability of the soluble iron complexes and iron colloids also suggest that the weaker soluble Fe complexes may be more bio-available, while the strongest colloids may be a major route for iron removal from oceanic waters. Investigations of the size classes of the dissolved organic iron thus can significantly increase our understanding of the oceanic iron cycle.

Description: Zonal wind anomalies in the western equatorial Atlantic during late boreal winter to early summer precondition boreal summer cold/warm events in the eastern equatorial Atlantic (EEA) that manifest in a strong interannual Atlantic cold tongue (ACT) variability. Local intraseasonal wind fluctuations, linked to the St. Helena anticyclone, contribute to the variability of cold tongue onset and strength, particularly during years with preconditioned shallow thermoclines. The impact of cold tongue sea surface temperature (SST) anomalies on the wind field in the Gulf of Guinea is assessed. It contributes to the northward migration of humidity and convection and possibly the West African monsoon (WAM) jump. Copyright @ 2010 Royal Meteorological Society

Description: The Mauritanian coastal area is one of the most biologically productive upwelling regions in the world ocean. Shipboard observations carried out during maximum upwelling season and short-term moored observations are used to investigate diapycnal mixing processes and to quantify diapycnal fluxes of nutrients. The observations indicate strong tide-topography interactions that are favored by near-critical angles occurring on large parts of the continental slope. Moored velocity observations reveal the existence of highly nonlinear internal waves and bores and levels of internal wave spectra are strongly elevated near the buoyancy frequency. Dissipation rates of turbulent kinetic energy at the slope and shelf determined from microstructure measurements in the upper 200 m averages to ɛ = 5 × 10−8 W kg−1. Particularly elevated dissipation rates were found at the continental slope close to the shelf break, being enhanced by a factor of 100 to 1000 compared to dissipation rates farther offshore. Vertically integrated dissipation rates per unit volume are strongest at the upper continental slope reaching values of up to 30 mW m−2. A comparison of fine-scale parameterizations of turbulent dissipation rates for shelf regions and the open ocean to the measured dissipation rates indicates deficiencies in reproducing the observations. Diapycnal nitrate fluxes above the continental slope at the base of the mixed layer yielding a mean value of 12 × 10−2 μmol m−2 s−1 are amongst the largest published to date. However, they seem to only represent a minor contribution (10% to 25%) to the net community production in the upwelling region.

Description: Accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes. Most proxies for temperature are not thermodynamically based, appear to be subject to biological processes, require regional calibrations, and/or are influenced by fluid composition. As a result, their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated. Independent proxies for past temperature could provide an important means of testing and/or expanding on existing reconstructions. Here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths, relate those abundances to independently estimated growth temperatures, and discuss the possible scope of equilibrium and kinetic isotope effects. The proportions of 13C–18O bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonatecontaining minerals (apatite from fish, reptile, and mammal teeth; calcitic brachiopods and molluscs; aragonitic coral and mollusks). Most species that exhibit non-equilibrium 18O/16O (d18O) and 13C/12C (δ13C) ratios are characterized by 13C–18O bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium, with possible exceptions among benthic foraminiferal samples from the Arctic Ocean where temperatures are near-freezing. Observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species.

Description: The European sprat (Sprattus sprattus) was a main target species of the German GLOBEC program that investigated the trophodynamic structure and function of the Baltic and North Seas under the influence of physical forcing. This review summarizes literature on the ecophysiology of sprat with an emphasis on describing how environmental factors influence the life-history strategy of this small pelagic fish. Ontogenetic changes in feeding and growth, and the impacts of abiotic and biotic factors on vital rates are discussed with particular emphasis on the role of temperature as a constraint to life-history scheduling of this species in the Baltic Sea. A combination of field and laboratory data suggests that optimal thermal windows for growth and survival change during early life and are wider for eggs (5–17 °C) than in young (8- to 12-mm) early feeding larvae (5–12 °C). As larvae become able to successfully capture larger prey, thermal windows expand to include warmer waters. For example, 12- to 16-mm larvae can grow well at 16 °C and larger, transitional-larvae and early juveniles display the highest rates of feeding and growth at ∼18–22 °C. Gaps in knowledge are identified including the need for additional laboratory studies on the physiology and behavior of larvae (studies that will be particularly critical for biophysical modeling activities) and research addressing the role of overwinter survival as a factor shaping phenology and setting limits on the productivity of this species in areas located at the northern limits of its latitudinal range (such as the Baltic Sea). Based on stage- and temperature-specific mortality and growth potential of early life stages, our analysis suggests that young-of-the year sprat would benefit from inhabiting warmer, near-shore environments rather than the deeper-water spawning grounds such as the Bornholm Basin (central Baltic Sea). Utilization of warmer, nearshore waters (or a general increase in Baltic Sea temperatures) is expected to accelerate growth rates but also enhance the possibility for density-dependent regulation of recruitment (e.g., top-down control of zooplankton resources) acting during the late-larval and juvenile stages, particularly when sprat stocks are at high levels. Highlights ► Field, laboratory and modeling research on the ecophysiology of all sprat life stages is summarized. ► Environmental factors influencing growth and survival are revealed. ► Ontogenetic changes in thermal tolerance and prey requirements constrain life cycle scheduling. ► Gaps in knowledge are identified and future research efforts recommended on sprat recruitment dynamics. ► Exploring seasonal energy allocation will allow a mechanistic understanding of climate impacts.

Description: Throughout the last decades there has been a world-wide, general warming trend. In this study, we use the example of the Baltic Sea to resolve the overall estimated temperature trend into smaller, meso-scale spatial units. Afterwards, we investigate the spatially resolved potential impact of the temperature trend on larval survival for two important fish species, cod and sprat. We used two different sets of hydrographic data: (i) long-term temporally and depth-resolved data measured in situ originating from one geographic position and (ii) long-term horizontally resolved data, originating from a circulation model. In contrast to basin-wide integrated results, our modelling approach revealed different results related to smaller spatial scales. In shallow and coastal areas non-significant long-term temperature trends were observed. In some cases even decreasing temperature trends were found. Average distribution maps (1973–2010) of cod and sprat eggs and larvae confirmed the higher importance of central, deep basins as nursery grounds. Applying the temperature trends when calculating cod larval window of opportunity values, resulted in decreased durations of 1–3 days (~ 3–13%) in most areas. Sprat larval window of opportunity values mainly increased up to 4 days (~ 45%), indicating a potential reproduction advantage of sprat over cod under anticipated future temperature increase. Highlights ► We resolve the overall positive temperature trend in the Baltic into meso-scale spatial units and investigate the impact on larval survival for two important fish species, cod and sprat. ► In shallow and coastal areas non-significant or even negative temperature trends occurred. ► Cod larval window of opportunity values decreased by 1–3 days (~ 3–13%). ► Sprat larval window of opportunity values increased up to 4 days (~ 45%). ► Sprat will have a reproduction advantage over cod under anticipated future temperature change.

Description: Basin modeling and cross-section restoration from the northern East China Sea Shelf Basin reveal the timing of trap formation and petroleum generation. Cross-section restoration suggest that extension started in the Late Cretaceous and was interrupted by inversion at the end of Miocene that created large anticline structures, providing numerous petroleum traps. One-dimensional basin modeling of the JDZ-VII-I well show that the main phase of oil generation in the synrift fluvial shales in the Jeju Basin occurred during the Early Oligocene–middle Miocene period, predating the regional inversion. Thus, potential for large oil accumulations in the southern part of the basin is probably limited. Most of the petroleum are likely to have flowed toward the basin margin as well as basin center until the Late Miocene because no structures were available to capture them. The formation of anticline structures overlapped and/or postdated the main phase of gas generation in the Jeju Basin. This is probably why the JDZ-VII-1 is gas-prone with the gas trapped mainly in the anticlinal structures formed by the tectonic uplift. The source rocks in the southwestern part of the Domi Basin are immature for petroleum generation.

Description: Water transported by slabs into the mantle at subduction zones plays key roles in tectonics, magmatism, fluid and volatiles fluxes, and most likely in the chemical evolution of the Earth's oceans and mantle. Yet, incorporation of water into oceanic plates before subduction is a poorly understood process. Several studies suggest that plates may acquire most water at subduction trenches because the ocean crust and uppermost mantle there are intensely faulted caused by bending and/or slab pull, and display anomalously low seismic velocities. The low velocities are interpreted to arise from a combination of fluid-filled fractures associated to normal faulting and mineral transformation by hydration. Mantle hydration by transformation of nominally dry peridotite to water-rich serpentinite could potentially create the largest fluid reservoir in slabs and is therefore the most relevant for the transport of water in the deep mantle. The depth of fracturing by normal-fault earthquakes is usually not well constrained, but could potentially create deep percolation paths for water that might hydrate up to tens of kilometers into the mantle, restrained only by serpentine stability. Yet, interpretation of deep intraplate mineral alteration remains speculative because active-source seismic experiments have sampled only the uppermost few kilometers of mantle, leaving the depth-extent of anomalous velocities and their relation to faulting unconstrained. Here we use a joint inversion of active-source seismic data, and both local and regional earthquakes to map the three dimensional distribution of anomalous velocities under a seismic network deployed at the trench seafloor. We found that anomalous velocities are restrained to the depth of normal-fault micro-earthquake activity recorded in the network, and are considerably shallower than either the rupture depth of teleseismic, normal-fault earthquakes, or the limit of serpentine stability. Extensional micro-earthquakes indicate that each fault in the region slips every 2–3 months which may facilitate regular water percolation. Deeper, teleseismic earthquakes are comparatively infrequent, and possibly do not cause significant fracturing that remains open long enough to promote alteration detectable with our seismic study. Our results show that the stability field of serpentine does not constrain the depth of potential mantle hydration.

Description: In this paper we used a steady-state ecosystem model that simulates both dissolved organic carbon (DOC) and nitrogen (DON) cycling to study how the planktonic community structure, nutrient availability, and dissolved organic matter (DOM) loading affect these cycles in idealized oceanic, coastal, and estuarine surface waters. The model was able to reproduce DOM and planktonic biomass distributions, uptake rates, and production rates (including DOM) that fell within ranges reported for oceanic, coastal, and estuarine systems. Using a sensitivity analysis we show that DOM cycling was intricately tied to the biomass concentration, distribution, and productivity of plankton. The efficiency of nutrient remineralization and the availability of inflowing nutrients and DON also played a large role in DOM cycling. In these simulations the largest autochthonous source of DOC was always phytoplankton exudation while important sources of DON varied considerably. In the oceanic simulations heterotrophic bacteria were particularly important for mediating DOM cycling because they were the primary agents that controlled nutrient recycling and supply (i.e., strong bottom-up control). In contrast, in the estuarine simulations mortality (mainly from grazing and viral lysis) had the most influence on DOM production. However, DOM cycling was generally less dependent on interactions between plankton in the estuarine case because of high nutrient and DOM loading. The coastal simulations were somewhere in between. In all simulations competition between different size classes of phytoplankton also played an important role in DOM cycling.

Description: Climate-dependent chemical weathering trends have a strong impact on the dissolved Pb isotopic composition of continental runoff during glacial terminations, so that this tracer can be used to reconstruct the impact of the North American deglaciation on aspects of freshwater runoff and ocean chemistry. Here we present authigenic Fe–Mn oxyhydroxide-derived Pb isotope records from lower Laurentian Fan sediments that trace the local deglacial continental runoff signal through the Gulf of St. Lawrence. We use these records to investigate changes in the Pb isotopic composition of the North American runoff, and their relationship to deglacial processes. The new Pb isotope records are very similar to those from the subtropical deep NW Atlantic locations, though the new data are at higher resolution and exhibit much greater amplitudes of change due to their Laurentide Ice Sheet-proximal setting. Unradiogenic compositions (206Pb/204Pb as low as 18.8 at 18.5 ka) during the latest glacial change towards highly radiogenic compositions during the early Holocene (206Pb/204Pb = 20.1 at 11.2 ka). Late Holocene 206Pb/204Pb values return to intermediate values around 206Pb/204Pb = 19.6. These new data support previous inferences that the Pb isotopic composition of the deep Atlantic is controlled during deglaciation by changes in the pattern and intensity of continental chemical weathering. In more detail, the most significant change in the entire Pb isotope record starts at 12.5 ka and lasts until about 11 ka. This observation, of strong Pb isotopic changes across a climatically cold period in the North Atlantic region, suggests that at this location Pb isotopic compositions recorded in deep marine authigenic Fe–Mn oxyhydroxides not only trace deglacial changes in chemical weathering intensity but also highly depend on major freshwater runoff routes in interior North America. Our data suggest a gradual opening of the eastward freshwater runoff route in the course of the Younger Dryas.

Description: Understanding the pre-anthropogenic Pb cycle of central North Pacific deep water has attracted a lot of attention in recent years, partly because of its unique geographical location in that it is a remote gyre system characterized by high dust fluxes and sluggish overturning circulation. However, the factors controlling Pb isotope evolution in this area over the Cenozoic are still controversial and various mechanisms have been proposed in previous studies. Here we report new Pb and Nd isotope time series of four ferromanganese crusts (two from the western Pacific near the Mariana arc and the other two from the central Pacific). Together with previously published records, we discuss for the first time the significance of a persistent and systematic Pb isotopic provinciality recorded by central North Pacific crusts over the Cenozoic. We propose that globally well mixed stratosphere volcanic aerosols could contribute Pb but have not been the major factors controlling the Pb isotope distribution in the central North Pacific over time. Island arc input (and probably enhanced hydrothermal input between about 45 and 20 Ma) likely controlled the Pb isotope provinciality and evolution prior to ~20 Ma, when coeval Pb isotope records in different crusts showed large differences and atmospheric silicate dust flux was extremely low. After the Eocene, in particular after 20 Ma, Asian dust input has become an isotopically resolvable source, while island arc-derived Pb has remained important to balance the dust input and to produce the observed Pb isotope distribution in the central North Pacific during this period.

Description: The objective of the present study was to determine the action of beta-glucans as feed additives on the gene expression profile of some inflammatory-related cytokines from common carp (Cyprinus carpio L) during the early stages of a non-lethal bacterial infection with Aeromonas salmonicida. beta-glucan (MacroGard (R)), was administered daily to carp (6 mg per kg body weight) in the form of supplemented commercial food pellets for 14 days prior to infection. Control and treated fish were then intraperitoneally injected with PBS or 4 x 10(8) bacteria per fish and were sampled at time 0 and 6 h, 12 h, I day, 3 days and 5 days post-injection. Head kidney and gut were collected and the gene expression patterns for tnf alpha 1, tnf alpha 2, il1 beta, il6 and il10 were analyzed by quantitative PCR. Results obtained showed that treatment with beta-glucans generally down-regulated the expression of all measured genes when compared to their corresponding controls. After injection, highest changes in the gene expression levels were obtained at 6 h: particularly, in head kidney there was higher up-regulation of tnfa1 and tnfa2 in infected fish fed beta-glucans in comparison to control feed: however, in gut there was a significant down-regulation of tnf alpha 1, tnf alpha 2, il1 beta and il6 in infected fish fed beta-glucans. Analysis of carp specific antibodies against A. salmonicida 30 days after injection revealed their levels were reduced in the infected beta-glucan group. In conclusion, a diet supplemented with beta-glucan (MacroGard (R)) reduced the gene expression levels of some inflammation-related cytokines in common carp. Such a response appears to be dependent of organ studied and therefore the immunostimulant may be preventing an acute and potential dangerous response in gut, whilst enhancing the inflammatory response in head kidney when exposed to A. salmonicida

Description: A realistic primitive-equation model of the Southern Ocean at eddying spatial resolution is used to examine the effect of ocean-surface-velocity dependence of the wind stress on the strength of near-inertial oscillations. Accounting for the ocean-surface-velocity dependence of the wind stress leads to a large reduction of wind-induced near-inertial energy of approximately 40 percent and of wind power input into the near-inertial frequency band of approximately 20 percent. A large part of this reduction can be explained by the leading-order modification to the wind stress if the ocean-surface velocity is included. The strength of the reduction is shown to be modulated by the inverse of the ocean-surface-mixed-layer depth. We conclude that the effect of surface-velocity dependence of the wind stress should be taken into account when estimating the wind-power input into the near-inertial frequency band and when estimating near-inertial energy levels in the ocean due to wind forcing.

Description: Thirty-two new single crystal ages document 400 000 years of widespread explosive volcanism of historically active Nemrut Volcano towering over huge alkaline Lake Van (Eastern Anatolia). The dated deposits were selected to monitor the volcanic and compositional evolution of Nemrut Volcano through time and thus to provide a rigorous temporal framework for the tephra record of the PaleoVan Drilling Project. Tephra samples were taken from large-volume deposits or those that occur in medial to distal localities, well-exposed stratigraphic sections or from the initial phase of an eruptive sequence. Mainly fallout deposits were chosen because most ignimbrites show more complex and corroded feldspar populations owing to compositional zoning and magma mixing. Moreover, fallout deposits held the promise to be more clearly identifiable with-and correlatable to-〉300 tephra layers in the PaleoVan drill cores, even though commonly in amounts marginal or insufficient in thickness to allow well-supported single crystal dating. The crystals dated are dominantly anorthoclase, the main phenoctyst phase in the trachytic to rhyolitic, slightly to strongly peralkaline Nemrut magmas. Ages obtained so far range from ca. 400 ka to ca. 30 ka for Nemrut Volcano. The causes of significant changes in the frequency, volume and composition of tephra layers per unit time are discussed in terms of external (erosion, climate changes, geodynamic factors) and internal forcing (changes in magma supply and composition and incubation periods preceding large volume rhyolitic eruptions). For example, the low frequency of tephra layers deposited prior to ca. 200 ka may be due to low explosive activity, severe erosion between MIS 9 and MIS 11, or both. Nevertheless, the overall frequency of explosive eruptions appears to have increased during the past ca. 200 ka. We also recognize a slight peak in explosive eruptions during warm periods (e.g. MIS 5 and MIS 7) and speculate on lithospheric unloading triggering increased partial melting or magma reservoir unloading following massive glacier melting. The ages of 5 dated ignimbrites span ca. 250 000 years suggesting that Nemrut Volcano went through a polycyclic evolution with multiple caldera collapses and major pyroclastic flow eruptions, the oldest dated so far as 265 ka. The widely held view of the impressive Nemrut Caldera now dated to have formed at ca. 30 ka, as the main paroxysmal event during the evolution of the volcano is no longer tenable. Distinct and coherent compositional characteristics, especially in trace element concentrations, characterize several groups of trachytic tephras. We speculate that the growth of Nemrut Volcano caused the isolation of the Lake Van basin. On account of their mineralogical (anorthoclase, hedenbergite, fayalite, aenigmatite) and alkalic chemical compositions and large volume, dated Nemrut fallout tephras are likely to represent excellent markers in lakes and other sites of paleoclimatological or archeological interest in neighboring countries to the northeast of Lake Van as far as the Caspian Sea in what may be called the East Anatolian Tephra Province

Description: We present results from an active-source, onshore–offshore seismic reflection/refraction transect acquired as part of the PETROBAR project (Petroleum-related studies of the Barents Sea region). The 700 km-long profile is oriented NW–SE, coincident with previously published multichannel seismic reflection profiles. We utilize layer-based raytracing in a Markov Chain Monte Carlo (MCMC) inversion to determine a probabilistic velocity model constraining the sedimentary rocks, crystalline crust, and uppermost mantle in a complex tectonic regime. The profile images a wide range of crustal types and ages, fromProterozoic craton to Paleozoic to early Cenozoic rift basins; and volcanics related to Eocene continental breakupwith Greenland. Our analyses indicate a complex architecture of the crystalline crust along the profile,with crystalline crustal thicknesses ranging from43 kmbeneath the Varanger Peninsula to 12 kmbeneath the Bjørnøya Basin. Assuming an original, post-Caledonide crustal thickness of 35 km in the offshore area, we calculate the cumulative thinning (β) factors along the entire profile. The average β factor along the profile is 1.7 ± 0.1, suggesting 211–243 km of extension, consistent with the amount of overlap derived from published plate reconstructions. Local β factors approach 3, where Bjørnøya Basin reaches a depth of more than 13 km. Volcanics, carbonates, salt, diagenesis and metamorphism make deep sedimentary basin fill difficult to distinguish from original, pre-rift crystalline crust, and thus actual stretching may in places exceed our estimates.

Description: We present the first neodymium isotope reconstruction of Mediterranean–Atlantic water exchange through the Moroccan (‘Rifian’) Corridor 8–5 Ma. This covers the late Miocene Messinian Salinity Crisis (MSC); a period when progressive tectonic restriction of the Mediterranean–Atlantic seaways resulted in extreme, basin-wide Mediterranean salinity fluctuations. The Rifian Corridor was one of these seaways and until now, relatively poor age constraints existed for the timing of Corridor closure, due to the impact of uplift and erosion on the sedimentary record. The bottom water Nd isotope record from the continuous Bou Regreg Valley succession in northwest Morocco allows us to explore corridor connectivity with the Atlantic. Data from the interior and Mediterranean edge of the Rifian Corridor (respectively, the Taza–Guercif and Melilla basins, northern Morocco) provide new information on corridor shallowing and the provenance of water flowing through the seaway. As a result, we can constrain the age of Rifian Corridor closure to 6.64–6.44 Ma. We also find no evidence of the siphoning of Atlantic waters through the seaway (7.20–6.58 Ma). Our results cannot exclude the possibility that at times during the Messinian Salinity Crisis, Mediterranean Outflow Water reached the Atlantic.

Description: The history of climate modeling begins with conceptual models, followed in the 19th century by mathematical models of energy balance and radiative transfer, as well as simple analog models. Since the 1950s, the principal tools of climate science have been computer simulation models of the global general circulation. From the 1990s to the present, a trend toward increasingly comprehensive coupled models of the entire climate system has dominated the field. Climate model evaluation and intercomparison is changing modeling into a more standardized, modular process, presenting the potential for unifying research and operational aspects of climate science

Description: This study presents a new estimate of the oceanic anthropogenic CO2(Cant) sink over the industrial era (1780 to present), from assimilation of potential temperature, salinity, radiocarbon, and CFC-11 observations in a global steady state ocean circulation inverse model (OCIM). This study differs from previous data-based estimates of the oceanic Cant sink in that dynamical constraints on ocean circulation are accounted for, and the ocean circulation is explicitly modeled, allowing the calculation of oceanic Cant storage, air-sea fluxes, and transports in a consistent manner. The resulting uncertainty of the OCIM-estimated Cant uptake, transport, and storage is significantly smaller than the comparable uncertainty from purely data-based or model-based estimates. The OCIM-estimated oceanic Cant storage is 160–166 PgC in 2012, and the oceanic Cant uptake rate averaged over the period 2000–2010 is 2.6 PgC yr−1 or about 30% of current anthropogenic CO2 emissions. This result implies a residual (primarily terrestrial) Cant sink of about 1.6 PgC yr−1 for the same period. The Southern Ocean is the primary conduit for Cant entering the ocean, taking up about 1.1 PgC yr−1 in 2012, which represents about 40% of the contemporary oceanic Cant uptake. It is suggested that the most significant source of remaining uncertainty in the oceanic Cant sink is due to potential variability in the ocean circulation over the industrial era.

Description: Contemporary genetic diversity is the product of both historical and contemporary forces, such as climatic and geological processes affecting range distribution and continuously moulded by evolutionary forces selection, gene flow and genetic drift. Predatory freshwater fishes, such as Northern Pike Esox lucius, commonly exhibit small population sizes, and several local populations are considered endangered. Pike inhabit diverse habitat types, including lakes, rivers and brackish marine waters, thus spanning from small isolated patches to large open marine systems. However, pike population structure from local to regional scales is relatively poorly described, in spite of its significance to developing conservation measures. We analysed microsatellite variation in a total of 1185 North European pike from 46 samples collected across both local and regional scales, as well as over time, to address two overarching questions: Is pike population structure associated with local and/or regional connectivity patterns, and which factors likely have the main influence on the contemporary distribution of genetic diversity? To answer this, we combined estimators of population diversity and structure to assess evidence of whether populations within (i) habitats, (ii) drainage systems and (iii) geographical regions are closer related than among these ranges, and whether patterns are temporally stable. Contrasting previous predictions that genetic drift obscures signals of postglacial colonisation history, we identified clear regional differences in population genetic signatures, suggesting a major effect of drainage divides on colonisation history and connectivity. However, several populations deviated from the general pattern, showing that local processes may be complex and need to be examined case-by-case.

Description: Sedimentation rates (corrected for compaction) from along the passive continental margin of Africa between the Equatorial Fracture Zone and Somalia are used to compare the rates of subsidence of the continental crust since early Mesozoic time. Three distinctive subsidence histories can be identified which correspond with basinal areas that have different structural styles: rifted (west coast), sheared (Equatorial and Agulhas fracture zones) and sunk (zones of vertical tectonics in eastern Africa). A comparison of subsidence rates with other tensional margins (NE USA and the North Sea) and a consideration of the plate tectonic history of the African margins leads to the proposal of a geo and thermodynamic model that takes cognizance of the worldwide mid-Cretaceous rheological discontinuity between taphrogenic and epeirogenic basin formation recognized by Kent, and the more generally accepted, purely plate tectonic driven model of margin subsidence. The new suggestion involves a lower Mesozoic worldwide rise in the geothermal gradient in the lithosphere which produces metamorphism of the base of the continental crust and initiates taphrogenesis along lineaments throughout Gondwanaland. A lowering of the geothermal gradient in the lower Cretaceous produces a switch to epeirogenic subsidence, driven solely by sediment loading and thermal contraction, by Aptian/Albian times. The thermal event facilitated continental separation, and sea floor spreading commenced locally at various times along the active taphrogenic belts. Local thermal and tectonic aberrations associated with this phenomenon over print onto the worldwide pattern of marginal basin subsidence. A further rise in the geothermal gradient may have been responsible for renewed taphrogenesis in eastern Africa in Tertiary times.

Description: Gas hydrate-related bottom-simulating reflectors mark the phase boundary between hydrate and free gas in the subsurface, and therefore may be used to estimate geothermal gradients and hence heat flow. The depth and temperature of the phase boundary depend on the composition of the hydrateforming gas and of the pore fluid. In the absence of direct sampling, these compositions remain unknown. We develop an alternative approach that is less sensitive to compositional uncertainties and can be applied when the bottom-simulating reflector is densely sampled in a region with significant seabed relief. We apply this approach to a three-dimensional seismic dataset from the eastern Black Sea.

Description: Stratospheric ozone depletion and emission of greenhouse gases lead to a trend of the southern annular mode (SAM) toward its high-index polarity. The positive phase of the SAM is characterized by stronger than usual westerly winds that induce changes in the physical carbon transport. Changes in the natural carbon budget of the upper 100 m of the Southern Ocean in response to a positive SAM phase are explored with a coupled ecosystem-general circulation model and regression analysis. Previously overlooked processes that are important for the upper ocean carbon budget during a positive SAM period are identified, namely, export production and downward transport of carbon north of the polar front (PF) as large as the upwelling in the south. The limiting micronutrient iron is brought into the surface layer by upwelling and stimulates phytoplankton growth and export production but only in summer. This leads to a drawdown of carbon and less summertime outgassing (or more uptake) of natural CO2. In winter, biological mechanisms are inactive, and the surface ocean equilibrates with the atmosphere by releasing CO2. In the annual mean, the upper ocean region south of the PF loses more carbon by additional export production than by the release of CO2 into the atmosphere, highlighting the role of the biological carbon pump in response to a positive SAM event.

Description: We combined data sets of measured sedimentary calcium carbonate (CaCO3) and satellite-derived pelagic primary production to parameterize the relation between CaCO3 content on the Antarctic shelves and primary production in the overlying water column. CaCO3 content predicted in this way was in good agreement with the measured data. The parameterization was then used to chart CaCO3 content on the Antarctic shelves all around the Antarctic, using the satellite-derived primary production. The total inventory of CaCO3 in the bioturbated layer of Antarctic shelf sediments was estimated to be 0.5 Pg C. This quantity is comparable to the total CO2 uptake by the Southern Ocean in only one to a few years (dependent on the uptake estimate and area considered), indicating that the dissolution of these carbonates will neither delay ocean acidification in this area nor augment the Southern Ocean CO2 uptake capacity.

Description: The evolution of ridge-hotspot systems is not well understood. In this investigation, satellite-derived marine gravity data are used in conjunction with underway bathymetric and magnetic anomaly profiles to investigate the nature of ridge-hotspot interaction at four sparsely explored systems in the Southern Ocean. These systems illustrate three different stages of ridge-hotspot interaction in which a migrating spreading center approaches a hotspot (Pacific-Antarctic/Louisville), passes over or is captured by the hotspot (Mid-Atlantic/Shona-Discovery), and ultimately migrates away from the hotspot (Southeast Indian/Kerguelen). All of these systems show some evidence of discrete ridge jumps in the direction of the hotspot as the spreading center attempts to relocate toward the hotspot by asymmetric spreading. Interestingly, these ridge jumps show no evidence of propagating offsets as have been seen on many other ridge-hotspot systems. A simple model predicts that typical plume excess temperatures can weaken the lithosphere sufficiently to promote asymmetric spreading and possibly allow a discrete ridge jump. The presence of previously uncharted, obliquely oriented aseismic ridges and gravity lineations between the ridge and the hotspot supports the notion of asthenospheric flux from the plume to the spreading center both before and after the time when the hotspot is ridge centered. The azimuths of the aseismic ridges cannot be explained by plate kinematics alone; they consistently extend from the ends toward the centers of the adjacent spreading segments suggesting some interaction between plume derived asthenospheric flux and local lithospheric structure. The features discussed here also indicate that the transfer of asthenospheric material from the plume to the spreading center is influenced by the local plate boundary configuration and interaction with transform offsets.

Description: Tectonic pseudotachylytes, i.e. quenched friction-induced silicate melts, record coseismic slip along faults and are mainly reported from the brittle crust in association with cataclasites. In this study, we document the occurrence of recrystallization of quartz to ultrafine-grained (grain size 1–2 μm) aggregates along microshear zones (50–150 μm thick) in the host rock adjacent to pseudotachylytes from two different faults within quartzite (Schneeberg Normal Fault Zone, Eastern Alps), and tonalite (Adamello fault, Southern Alps) in the brittle crust. The transition from the host quartz to microshear zone interior includes: (i) formation of high dislocation densities; (ii) fine (0.3–0.5 μm) polygonization to subgrains defined by disordered to well-ordered dislocation walls; (iii) development of a mosaic aggregate of dislocation-free new grains. The crystallographic preferred orientation (CPO) of quartz towards the microshear zone shows a progressive misorientation from the host grain, by subgrain rotation recrystallization, to a nearly random CPO possibly related to grain boundary sliding. These ultrafine aggregates appear to be typically associated with pseudotachylytes in nature. We refer the crystal plastic deformation of quartz accompanied by dramatic grain size refinement to the coseismic stages of fault slip due to high differential stress and temperature transients induced by frictional heating. Microshear zones localized on precursory fractures developed during the stages of earthquake rupture propagation and the very initial stages of fault slip. Thermal models indicate that the process of recrystallization, including recovery processes, occurred in a time lapse of a few tens of seconds.

Description: We have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles. Regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models; we avoided those data where purely conductive heat flow suggested temperatures more than about 1000°C, substantially higher than solidus temperatures and outside the range of validity of heat flow models. The resulting plots of log conductivity σ versus 1/T demonstrate that even low-conductivity layers (LCL) have conductivities several orders of magnitude higher than dry laboratory samples and that the data can be represented by straight line fits. In addition, technically active regions show systematically higher conductivities than do shield areas. Because volatiles are usually lost in laboratory measurements and their absence is a principal difference between laboratory and field conditions, these materials probably account for the relatively higher conductivities of rocks in situ in the crust; free water in amounts of 0.01–0.1% in fracture porosity could explain crustal conductivities. Other possibilities are graphite, hydrated minerals in rare instances, and sulfur in combination with other volatiles. As most of the temperatures are less than 700°C, partial melting seems likely only in regions of highest heat flow where the conductive temperature profiles are inappropriate. Another result is that at a given temperature, crustal high-conductivity layers (HCL) are more conductive by another order of magnitude and show more scatter than do LCL's. Because the differences between HCL's and LCL's are independent of temperature, we must invoke more than temperature increases as a cause for large conductivity increases; increased fluid concentration in situ seems a probable cause for enhanced conductivities in HCL's. From the point of view of these observations, it does not matter whether the fluids are in communication with the surface or trapped at lithostatic pressures.

Description: The exchange of inorganic nutrients; ammonium, nitrate and reactive phosphate between burrows of the infaunal polychaete Nereis virens Sars and the overlying water was assessed using V-shaped sediment cores. Exchange was determined by monitoring ventilation current and nutrient concentration of in- and excurrent water. Ammonium supply appeared independent of overlying water concentrations, showing a constant release of 0.5 μmol·h−1 (for a 2-g individual + burrow system) at concentrations from 2 to 87 μM. Of this release ≈40% originated from worm excretion, and the rest from microbial mineralization. Nitrate and phosphate exchange appeared very sensitive to overlying water concentrations, having equilibrium (zero flux) at 10–15 and 3 μM, respectively. Below these concentrations nitrate showed a slight release (due to nitrification), whereas phosphate was released at a rate of 3.2 × 10−2 μmol·h−1 at 1 μM (mineralization and desorption). Above equilibrium they both were removed during water passage through worm burrows, reaching 0.4 μmol·h−1 for nitrate at 107 μM (nitrate reduction) and 3.7 × 10−2 μmol·h−1 for phosphate at 5.6 μM (adsorption processes). The burrow system apparently acted as a buffer for phosphate and, to some degree, nitrate in the overlying water. At the study site (Norsminde Fjord estuary) nereid burrows were estimated to increase the sediment-water interface 150%. About 17% of the water column was cycled through the sediment by Nereis each day. The worm + burrow system was estimated to release 95 μmol· m−2·h−1 ammonium to the overlying water, which was ≈76–90% of the total release of ammonium from the sediment (30–36% was worm excretion).

Description: Before making a critical evaluation of the crude oil and natural gas prospects for the years to the end of the century, it is necessary to review the geology and structure of the three German hydrocarbon-producing provinces. Furthermore, past exploration, production and reserves should be discussed. The three hydrocarbon-producing provinces are: the NW German Basin, the Upper Rhine Graben and the Molasse Basin, which together make up about 41% of West German territory (Fig. 1). The NW German Basin contains a sedimentary sequence over 8,000 m thick ranging in age from Permian to Quaternary. Gas and oil, the two natural hydrocarbons, are generally confined to separate lower and higher stratigraphic levels respectively (Fig. 2). The NW German Basin is the most important prospective area in West Germany. It extends into the North Sea. The tectonic rift feature of the Upper Rhine Graben originated in the Eocene. The Tertiary fill is over 4,000 m thick. Oil is found mainly in Mesozoic, Eocene and Oligocene rocks; the Miocene and Pliocene reservoir rocks contain natural gas almost exclusively (Fig. 3). The Molasse Basin is part of the foredeep north of the Alpine and Carpathian mountain ranges. The basin is filled with Upper Eocene to Pliocene and Quaternary sediments which, near the Alpine nappes, reach a thickness of over 5,000m (Fig. 4). During this century there were peaks in annual oil-production in 1910, 1940 and 1968 (see Fig. 5). The 1910 peak was the result of drilling activity in the Wietze oilfield. During the period 1934–1945, government financial aid was made available for drilling exploration wells. The success of this collaboration is demonstrated by the oil output in 1940 of 1 × 106 t. After World War II, many different types of oil-bearing structure were found, particularly by reflection seismic techniques in conjunction with detailed stratigraphical and palaeogeographical investigations. The success achieved can be seen by the peak of 8 × 106 t oil production for 1968 (Fig. 5) and in the growth of oil reserves (Fig. 7). Intensive exploration also enabled many new gasfields to be developed, especially in the deeper horizons of the NW German Basin. In 1971, estimated gas reserves reached 360 × 109 m3 (Fig. 11), and annual gas production in 1979 was 20.7 × 109 m3 (731 Bcf) (Fig. 9). There is, no doubt, still scope for the discovery and exploitation of oil and gas in Germany, especially in the NW German Basin where the best prospects for the future lie. This is borne out by two recent offshore oil discoveries and also by the successful application of enhanced recovery methods in the oilfields. The chances of finding more gas at the lower stratigraphic levels are promising now that gas has been discovered in the deeper parts of the Permian basin. The results of massive-hydraulic-fracturing tests in low-permeability pay-horizons are also encouraging. The deeper parts of oil- and gas-producing basins contain interesting prospects and have yet to be tested by ultra-deep wells. Provided that the economic climate remains favourable, there should be no difficulty in finding and supplying German oil and gas in the future. Geologically and technically possible reserves should be converted into proven and/or probable reserves. German crude oil will be available for several years beyond the year 2000, and German natural gas for a far longer time. A production rate of 19 to 20 × 109 m3 of gas per annum is feasible over the next twenty years, and oil production will probably not sink below 3 × 106 t/a in this period.

Description: The combination of the Sunda megathrust and the (strike-slip) Sumatran Fault (SF) represents a type example of slip-partitioning. However, superimposed on the SF are geometrical irregularities that disrupt the local strain field. The largest such feature is in central Sumatra where the SF splits into two fault strands up to 35 km apart. A dense local network was installed along a 350 km section around this bifurcation, registering 1016 crustal events between April 2008 and February 2009. 528 of these events, with magnitudes between 1.1 and 6.0, were located using the double-difference relative location method. These relative hypocentre locations reveal several new features about the crustal structure of the SF. Northwest and southeast of the bifurcation, where the SF has only one fault strand, seismicity is strongly focused below the surface trace, indicating a vertical fault that is seismogenic to ∼15 km depth. By contrast intense seismicity is observed within the bifurcation, displaying streaks in plan and cross-section that indicate a complex system of faults bisecting the bifurcation. In combination with analysis of topography and focal mechanisms, we propose that the bifurcation is a strike-slip duplex system with complex faulting between the two main fault branches.

Description: Acoustic basement lies at an average of between 6.0 and 6.5 sec two-way time below sea level in the southern Rockall Trough and northern Porcupine Abyssal Plain. The overlying sedimentary succession reaches maximum thicknesses of at least 4.0 sec, and can be divided by 3 regionally-developed seismic reflecting horizons, which are used as a framework to establish an acoustic stratigraphy for the area by selecting three “type” seismic sections. These reflectors are named, in ascending order, Shackleton, Charcot and Challenger. The area is crossed by E—W basement high structures, the Clare Lineament (which may be an easterly extension of the Charlie Gibbs Fracture Zone), that separates the Porcupine Abyssal Plain from the eastern part of southern Rockall Trough. Under the latter, the post-Shackleton acoustic sequence is thickened, as if dammed to the north of the Clare Lineament, whilst a further thickening, above reflector Charcot, occurs along a NE—SW line somewhat farther north into the southern Rockall Trough. This can also be related to shallow-lying acoustic basement features. Pre-Shackleton sediments overlie a very irregular basement topography. The acoustic characters of the various sediment packages are described and it is speculated that major changes in the sedimentary environments took place across reflectors Shackleton and Challenger, the latter probably establishing the modern bottom current circulation patterns. No ages can be unequivocally assigned to the main reflectors, but previously published data suggest a late Eocene—Oligocene age for Challenger. Possible lavas or sills are identified in the succession between reflectors Shackleton and Charcot.

Description: Isopach asymmetry, and sediment component changes in DSDP cores from the SE Atlantic (Orange Basin) support the hypothesis of major drainage system changes in SW Africa during late Cretaceous—Cenozoic time. This involved alternations in the use of the 28°S (modern Orange River) and 31°S (modern Olifants River) exit points across the western escarpment by rivers carrying run-off from the Upper Orange/Vaal catchment areas, as well as radical re-organizations of internal drainage geometry. It is postulated that during late Cretaceous times the 28°S exit was used, with the Middle Orange River following a course in the interior well to the south (up to 150 km) of its modern channel. Sediment discharge rates from this river were relatively high (at least 10 × 106 m3 yr−1), and resulted in rapid advancement of the continental margin sediment prism west of the mouth by large-scale slumping. The Palaeogene Orange/Vaal river exit was via the 31°S escarpment crossing, and during the later part of this period, the Cape Canyon was cut across the continental shelf and slope. A significant reduction in sediment discharge (to 2.0 × 106 m3 yr−1) suggests that the Lower Tertiary climate for SW Africa was drier than that of late Cretaceous times. However, aridity did not commence until late Miocene times, when the Orange/Vaal discharge had switched back to the 28°S exit. Modern sediment discharge rates (6.5 × 106 m3 yr−1) are relatively high and reflect soil erosion caused by agricultural activity. The two major alterations in exit point of the Orange/Vaal (late Cretaceous—early Tertiary, and late Oligocene—early Miocene) are related to periods of low sea level, which promoted river capture adjacent to the western escarpment. An additional factor in the first course change may have been the disruption of the Middle Orange channel by late Cretaceous igneous intrusions. Less important internal reorganizations of the drainage system are postulated in late Miocene—Pleistocene times. Economic implications for offshore diamond distribution are briefly mentioned.

Description: Large Neogene slumps have affected over 260,000 km2 of the outer continental margin and adjacent Cape Basin off southwestern Africa. Individual structures cover areas up to 68,700 km2 and proximally are commonly composed of huge rotated sediment blocks up to 450 m thick and several kilometers across. Seismic shocks, possibly in conjunction with lower-slope undercutting by bottom-current erosion, are suggested as possible trigger mechanisms for these features which are all thought to be post-Pliocene (possibly Pleistocene) in age. Older slumps are also recognized along the margin and four cycles of sedimentation/slumping are identified: early Upper Cretaceous (I); late Upper Cretaceous (II); Palaeogene (III); and Neogene (IV). In the main part of the Orange Basin depocentre (west of Childs Bank) the Cretaceous slump styles are thought to represent Mississippi delta-type down-slope sediment cascades (with reverse faulting and mud diapirism) over 1 km thick which resulted from very rapid dumping of terrigenous material from the Orange River. Cainozoic slumps show a different tectonic style and locus and this is thought to reflect a change in sedimentation patterns which resulted from lower terrigenous input onto the margin, higher biogenic/authigenic sedimentation, and slowed crustal subsidence. A connection possibly exists between low sea level stands and the Cainozoic episodes of slumping.

Description: Ferromanganese (Fe–Mn) crusts are strongly enriched relative to the Earth's lithosphere in many rare and critical metals, including Co, Te, Mo, Bi, Pt, W, Zr, Nb, Y, and rare-earth elements (REEs). Fe–Mn nodules are strongly enriched in Ni, Cu, Co, Mo, Zr, Li, Y, and REEs. Compared to Fe–Mn crusts, nodules are more enriched in Ni, Cu, and Li, with subequal amounts of Mo and crusts are more enriched in the other metals. The metal ions and complexes in seawater are sorbed onto the two major host phases, FeO(OH) with a positively charged surface and MnO2 with a negatively charged surface. Metals are also derived from diagenetically modified sediment pore fluids and incorporated into most nodules. Seafloor massive sulfides (SMS), especially those in arc and back-arc settings, can also be enriched in rare metals and metalloids, such as Cd, Ga, Ge, In, As, Sb, and Se. Metal grades for the elements of economic interest in SMS (Cu, Zn, Au, Ag) are much greater than those in land-based volcanogenic massive sulfides. However, their tonnage throughout the global ocean is poorly known and grade/tonnage comparisons with land-based deposits would be premature. The Clarion–Clipperton Fe–Mn Nodule Zone (CCZ) in the NE Pacific and the prime Fe–Mn crust zone (PCZ) in the central Pacific are the areas of greatest economic interest for nodules and crusts and grades and tonnages for those areas are moderately well known. We compare the grades and tonnages of nodules and crusts in those two areas with the global terrestrial reserves and resources. Nodules in the CCZ have more Tl (6000 times), Mn, Te, Ni, Co, and Y than the entire global terrestrial reserve base for those metals. The CCZ nodules also contain significant amounts of Cu, Mo, W, Li, Nb, and rare earth oxides (REO) compared to the global land-based reserves. Fe–Mn crusts in the PCZ have significantly more Tl (1700 times), Te (10 times more), Co, and Y than the entire terrestrial reserve base. Other metals of significance in the PCZ crusts relative to the total global land-based reserves are Bi, REO, Nb, and W. CCZ nodules and PCZ crusts are also compared with the two largest existing land-based REE mines, Bayan Obo in China and Mountain Pass in the USA. The land-based deposits are higher grade but lower tonnage deposits. Notably, both land-based deposits have 〈 1% heavy REEs (HREEs), whereas the CCZ has 26% HREEs and the PCZ, 18% HREEs; the HREEs have a much greater economic value. Radioactive Th concentrations are appreciably higher in the land-based deposits than in either type of marine deposit. A discussion of the differences between terrestrial and marine impacts and mine characteristics is also presented, including the potential for rare metals and REEs in marine deposits to be recovered as byproducts of mining the main metals of economic interest in nodules and crusts.

Description: Correlations between particulate organic carbon (POC) and mineral fluxes in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. A recent study demonstrated regional variability in the effect of ballast minerals on the flux of POC in the deep ocean. We have undertaken a similar analysis of shallow export data from the Arctic, Atlantic, and Southern Oceans. Mineral ballasting is of greatest importance in the high-latitude North Atlantic, where 60% of the POC flux is associated with ballast minerals. This fraction drops to around 40% in the Southern Ocean. The remainder of the export flux is not associated with minerals, and this unballasted fraction thus often dominates the export flux. The proportion of mineral-associated POC flux often scales with regional variation in export efficiency (the proportion of primary production that is exported). However, local discrepancies suggest that regional differences in ecology also impact the magnitude of surface export. We propose that POC export will not respond equally across all high-latitude regions to possible future changes in ballast availability.

Description: Because the vast majority of species are well diverged, relatively little is known about the genomic architecture of speciation during the early stages of divergence. Species within recent evolutionary radiations are often minimally diverged from a genomic perspective, and therefore provide rare opportunities to address this question. Here, we leverage the hamlet radiation (Hypoplectrus spp., brightly coloured reef fishes from the tropical western Atlantic) to characterize genomic divergence during the early stages of speciation. Transect surveys and spawning observations in Belize, Honduras and Panama confirm that sympatric barred (H. puella), black (H. nigricans) and butter (H. unicolor) hamlets are phenotypically distinct and reproductively isolated, although hybrid spawnings and individuals with intermediate phenotypes are seen on rare occasions. A survey of approximately 100 000 restriction site-associated SNPs in 126 samples from the three species across the three replicate populations reveals extremely slight genomewide divergence among species (FST = 0.0038), indicating that ecomorphological differences and functional reproductive isolation are maintained in sympatry in a backdrop of extraordinary genomic similarity. Nonetheless, a very small proportion of SNPs (0.05% on average) are identified as FST outliers among sympatric species. Remarkably, a single SNP is identified as an outlier in repeated populations for the same species pair. A minicontig assembled de novo around this SNP falls into the genomic region containing the HoxCa10 and HoxCa11 genes in 10 teleost species, suggesting an important role for Hox gene evolution in this radiation. This finding, if confirmed, would provide a better understanding of the links between micro- and macroevolutionary processes.

Description: The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33°58′S and 57°33′S along the Greenwich Meridian during the austral summer 2008 in the framework of the International Polar Year. DCo concentrations were measured by flow-injection analysis and chemiluminescence detection in filtered (0.2 μm), acidified and UV-digested samples at 12 deep stations in order to resolve the several biogeochemical provinces of the Antarctic Circumpolar Current and to assess the vertical and frontal structures in the Atlantic sector of the Southern Ocean. We measured DCo ranging from 5.73 ± 1.15 pM to 72.9 ± 4.51 pM. The distribution of DCo was nutrient-like in surface waters of the subtropical domain with low concentrations in the euphotic layer due to biological uptake. The biological utilization of dissolved cobalt was proportional to that of phosphate in the subtropical domain with a DCo:HPO42− depletion ratio of ~ 44 μM M−1. In deeper waters the distribution indicated remineralization of DCo and inputs from the margins of South Africa with lateral advection of enriched intermediate and deep waters to the southeastern Atlantic Ocean. In contrast the vertical distribution of DCo changed southward, from a nutrient-like distribution in the subtropical domain to scavenged-type behavior in the domain of the Antarctic Circumpolar Current and conservative distribution in the Weddell Gyre. There the cycle of DCo featured low biological removal by Antarctic diatoms with input to surface waters by snow, removal in oxygenated surface waters, and dissolution and stabilization in the low-oxygenated Upper Circumpolar Deep Waters. DCo distributions and physical hydro-dynamics features also suggest inputs from the Drake Passage and the southwestern Atlantic to the 0° meridian along the eastward flow of the Antarctic Circumpolar Current. Bottom enrichment of DCo in the Antarctic Bottom Waters was also evident, together with increasing water-mass pathway and aging, possibly due to sediment resuspension and/or mixing with North Atlantic Deep waters in the Cape Basin. Overall atmospheric input of soluble Co by dry aerosols to the surface waters was low but higher in the ACC domain than in the northern part of the section. At the highest latitudes, it is possible that snowfall could be a source of DCo to surface waters. Tentative budgets for DCo in the mixed layer of the subtropical and the ACC domains have been constructed for each biogeochemical region encountered during the cruise. The estimated DCo uptake flux was found to be the dominant cobalt flux along the section. This flux decreases southward, which is consistent with the observations that DCo shows a southward transition from nutrient-like towards conservative distribution in the mixed layer.

Description: In this study we first evaluate the small-scale spatial variability of particulate export, using a set of synoptic thorium-234 activity observations sampled within a one-degree radius. These data show significant variability of surface thorium activity on scales of the order of 100 km (∼270–550 dpm m−3). This patchiness of export potentially affects the robustness of point observations and our interpretation of them. Motivated by these observations we subsequently couple an explicit model of thorium-234 dynamics to a coupled physical–biogeochemical basin model capable of resolving these small-scales. The model supports the observations in displaying marked thorium variability on spatial scales of the order of 100 km and smaller, with highest values in the regions of large eddy kinetic energy and large primary productivity. The model is also used to quantify the impact of small-scale variability on export estimates. Our model shows that the primary source of error associated with the presence of small-scale spatial variability is related to the standard assumptions of steady state and non-steady state (〉40% during bloom condition). The non-steady state method can misinterpret variations due to patchiness in thorium activity as temporal changes and lead to errors larger than those introduced by the simpler steady state approach. We show that the non-steady state approach could improve the flux estimates in some cases if the sampling was conducted in a Lagrangian framework. Undersampling the spatial variability results in further bias (〉20%) that can be reduced when the sampling density is increased. Finally, errors due to the dynamical transport of thorium associated with small-scale structures are relatively low (〈20%) except in regions of high eddy kinetic energy.

Description: The role of biominerals in driving carbon export from the surface ocean is unclear. We compiled surface particulate organic carbon (POC), and mineral ballast export fluxes from 55 different locations in the Atlantic and Southern Oceans. Substantial surface POC export accompanied by negligible mineral export was recorded implying that association with mineral phases is not a precondition for organic export to occur. The proportion of non-mineral associated sinking POC ranged from 0 to 80% and was highest in areas previously shown to be dominated by diatoms. This is consistent with previous estimates showing that transfer efficiency in such regions is low. However we propose that, rather than the low transfer efficiency arising from diatom blooms being inherently characterized by poorly packaged aggregates which are efficiently exported but which disintegrate readily in mid water, it is due to such environments having very high levels of unballasted organic C export.

Description: The simultaneous estimation of particulate organic carbon (POC), particulate inorganic carbon (PIC) and biogenic silica (BSi) export fluxes is key to the study of carbon export due to the hypothesized role of biominerals in the sinking of organic particles. This paper presents of the first attempts to measure downward fluxes of POC, PIC and BSi from the surface ocean using both the 234Th-238U and the 210Po-210Pb disequilibria and drifting sediments trap synchronously at the Porcupine Abyssal Plain in summer 2009. The combined use of the three techniques allowed us to analyze their suitability not only for POC flux estimates, but also as tracers of PIC and BSi fluxes. POC and biomineral/radionuclide ratios were measured in two size fractions to better understand differences between 234Th derived export and 210Po derived export. 210Po derived POC and biomineral fluxes were unexpectedly closer to POC and biomineral fluxes recorded by sediment traps than 234Th derived POC and biomineral fluxes which were higher than obtained from the other two approaches. We suggest that 210Po, because of its biogeochemical behavior, is a better proxy for POC and mineral fluxes than is 234Th in post bloom conditions. The contribution of smaller (1–53 μm) particles to flux is also considered in order to explain the differences in derived fluxes.

Description: The final phase of the closure of the Panamanian Gateway and the intensification of Northern Hemisphere Glaciation (NHG) both occurred during the Late Pliocene. Glacial–interglacial (G–IG) variations in sea level might, therefore, have had a significant impact on the remaining connections between the East Pacific and the Caribbean. Here, we present combined foraminiferal Mg/Ca and δ 18O measurements from Ocean Drilling Program (ODP) Site 1241 from the East Pacific and ODP Site 999 from the Caribbean. The studied time interval covers the first three major G–IG Marine Isotope Stages (MIS 95–100, ∼2.5 Ma∼2.5 Ma) after the intensification of NHG. Analyses were performed on the planktonic foraminifera Neogloboquadrina dutertrei and Globigerinoides sacculifer, representing water mass properties in the thermocline and the mixed-layer, respectively. Changes in sea water temperature, relative salinity, and water column stratification strongly suggest that the Panamanian Gateway temporarily closed during glacial MIS 98 and 100, as a result of changes in ice volume equivalent to a drop in sea level of 60–90 m. Reconstructed sea surface temperatures (SST) from G. sacculifer show a glacial decrease of 2.5 °C at Site 1241, but increases of up to 3 °C at Site 999 during glacial MIS 98 and 100 suggesting that the Panamanian Gateway closed during these glacial periods. The Mg/Ca-temperatures of N. dutertrei remain relatively stable in the East Pacific, but do show a 3 °C warming in the Caribbean at the onset of these glacial periods suggesting that the closing of the gateway also changed the water column stratification. We infer that the glacial closure of the gateway allowed the Western Atlantic Warm Pool to extend into the southern Caribbean, increasing SST (G. sacculifer) and deepening the thermocline (N. dutertrei). Additionally, ice volume appears to have become large enough during MIS 100 to survive the relatively short lasting interglacial MIS 99 so that the gateway remained closed. Towards the end of MIS 98, during MIS 97 and into MIS 96 temperatures on both sides are mostly similar suggesting water masses exchanged again. Additionally, Caribbean variations in SST and δ18Owater follow a precession-like cyclicity rather than the obliquity-controlled variations characteristic of the East Pacific and many other tropical areas, suggesting that regional atmospheric processes related to the trade winds and the InterTropical Convergence Zone (ITCZ) had a dominant impact in the Caribbean.

Description: A numerical algorithm based on Fermat's Principle was developed to simulate the propagation of Global Positioning System (GPS) radio signals in the refractivity field of a numerical weather model. The unique in the proposed algorithm is that the ray-trajectory automatically involves the location of the ground-based receiver and the satellite, i.e. the posed two-point boundary value problem is solved by an implicit finite difference scheme. This feature of the algorithm allows the fast and accurate computation of the signal travel-time delay, referred to as Slant Total Delay (STD), between a satellite and a ground-based receiver. We provide a technical description of the algorithm and estimate the uncertainty of STDs due to simplifying assumptions in the algorithm and due to the uncertainty of the refractivity field. In a first application, we compare STDs retrieved from GPS phase-observations at the German Research Centre for Geosciences Potsdam (GFZ STDs) with STDs derived from the European Center for Medium-Range Weather Forecasts analyses (ECMWF STDs). The statistical comparison for one month (August 2007) for a large and continuously operating network of ground-based receivers in Germany indicates good agreement between GFZ STDs and ECMWF STDs; the standard deviation is 0.5% and the mean deviation is 0.1%.

Description: In the vast Low Nutrient Low-Chlorophyll (LNLC) Ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low, and atmospheric contribution of nutrients may be one order of magnitude greater over short timescales. The short turnover time of atmospheric Fe and N supply (〈1 month for nitrate) further supports deposition being an important source of nutrients in LNLC regions. Yet, the extent to which atmospheric inputs are impacting biological activity and modifying the carbon balance in oligotrophic environments has not been constrained. Here, we quantify and compare the biogeochemical impacts of atmospheric deposition in LNLC regions using both a compilation of experimental data and model outputs. A metadata-analysis of recently conducted field and laboratory bioassay experiments reveals complex responses, and the overall impact is not a simple “fertilization effect of increasing phytoplankton biomass” as observed in HNLC regions. Although phytoplankton growth may be enhanced, increases in bacterial activity and respiration result in weakening of biological carbon sequestration. The application of models using climatological or time-averaged non-synoptic deposition rates produced responses that were generally much lower than observed in the bioassay experiments. We demonstrate that experimental data and model outputs show better agreement on short timescale (days to weeks) when strong synoptic pulse of aerosols deposition, similar in magnitude to those observed in the field and introduced in bioassay experiments, is superimposed over the mean atmospheric deposition fields. These results suggest that atmospheric impacts in LNLC regions have been underestimated by models, at least at daily to weekly timescales, as they typically overlook large synoptic variations in atmospheric deposition and associated nutrient and particle inputs. Inclusion of the large synoptic variability of atmospheric input, and improved representation and parameterization of key processes that respond to atmospheric deposition, is required to better constrain impacts in ocean biogeochemical models. This is critical for understanding and prediction of current and future functioning of LNLC regions and their contribution to the global carbon cycle.

Description: The impact of mesoscale activity on phytoplankton and nutrient distribution in the Mozambique Channel was simulated by coupling a biogeochemical model (PISCES) with a regional oceanic model (ROMS). Examples of the effects of eddies on the biogeochemistry of the Mozambique Channel are presented to illustrate the complexity of the system. In the model, several cyclonic eddies were found with low concentrations of chlorophyll at their cores, which contrasts with previous studies in the open ocean. In addition, several anticyclonic eddies were simulated with high concentrations of chlorophyll at their cores. Phytoplankton growth within these mesoscale features (both cyclonic and anticyclonic eddies) occurred in response to nutrient injection into the euphotic zone by advection, and subsequent retention of surrounding nutrient-rich waters within eddies. Offshore nutrient distributions depended strongly on lateral advection of nutrient-rich water from the coastal regions, induced by eddy interaction with the shelf. The environmental conditions at the locations where eddies were generated had an important effect on nutrient concentrations within these structures.

Description: Many biological seep studies focused on the distribution, structure, nutrition and food web architecture of seep communities as well as on their interaction with the seep geochemistry. However, overall respiration at cold seeps received only little attention. We conducted in-situ oxygen flux measurements in combination with ex-situ oxygen micro-profiles, respiration measurements, as well as rate determinations of microbial methane and sulfate turnover to assess respiration pathways as well as carbon turnover at a seep habitat that was recently discovered alongside the Hikurangi Margin offshore northern New Zealand. This habitat is dominated by dense beds of tube-building, heterotrophic ampharetid polychaetes. Average total oxygen uptake (TOU) from this habitat was very high (83.7 mmol m− 2 day− 1). TOU at a non-seep reference site ranged between 2.7 and 5.8 mmol m− 2 day− 1. About 37% (30.8 mmol m− 2 day− 1) of the average TOU was consumed by ampharetids. Considering mean diffusive oxygen uptake (8.5 mmol m− 2 day− 1) the remaining fraction of ~ 53% of the TOU (44.4 mmol m− 2 day− 1) might be explained by respiration of epibenthic organisms as well as aerobic methane and sulfide oxidation at the sediment–water interface. The strongly negative carbon isotopic signatures (− 52.9 ± 5‰ VPDB) of the ampharetid tissues indicate a methane derived diet. However, carbon production via anaerobic oxidation of methane (AOM) was too low (0.1 mmol C m− 2 day− 1) to cover the mean carbon demand of the ampharetid communities (21 mmol C m− 2 day− 1). Likely, organic carbon generated via aerobic methane oxidation represents their major carbon source. This is in contrast to other seep habitats, where energy bound in methane is partly transferred to sulfide via AOM and finally consumed by sulfide-oxidizing chemoautotrophs providing carbon that subsequently enters the benthic food web.

Description: Summary 1. Parasitized females in mammals, fish and birds can enhance the immune defence of their offspring by transferring specific antibodies for the embryo. Likewise, social insect mothers transfer immunity despite the fact that invertebrates lack antibodies. 2.  Female trans-generational immune priming is consistent with parental investment theory, because mothers invest more into rearing their offspring than fathers. However, when immune priming is not directly linked to parental care, as is often the case in insects that abandon their eggs after oviposition, both sexes might benefit from protecting their offspring. 3. Using the red flour beetle, Tribolium castaneum, we show that after parental exposure to heat-killed bacteria, trans-generational immune priming occurs through fathers as well as mothers. 4. This novel finding challenges the traditional view that males provide only genes to their offspring in species without paternal care, and raises the possibility of a division of tasks with respect to immune protection between parents.

Description: This study explores the effects of the Changjiang (also called the Yangtze River) river discharge (CRD) on the density stratifications and associated sea surface temperature (SST) changes using a global ocean general circulation model with regional focus on the Yellow and East China Seas (YECS). It is found that CRD increases the SST in summer through a barrier layer (BL) formation that tends to enhance stratification at the mixed layer base, and thus reduces both vertical mixing and entrainment. This process is effective, particularly in August, after the CRD reaches its maximum in July. The SST difference between the composites of flood and drought years confirms that the surface warming is related to surface freshening by the CRD. This result suggests that the BL induced by the CRD is an important contributor to the surface heat budget in the YECS.

Description: The importance of the Gulf Stream Extension region in climate and seasonal prediction research is being increasingly recognised. Here we use satellite-derived eddy momentum fluxes to drive a shallow water model for the North Atlantic Ocean that includes the realistic ocean bottom topography. The results show that the eddy momentum fluxes can drive significant transport, sufficient to explain the observed increase in transport of the Gulf Stream following its separation from the coast at Cape Hatteras, as well as the observed recirculation gyres. The model also captures recirculating gyres seen in the mean sea surface height field within the North Atlantic Current system east of the Grand Banks of Newfoundland, including a representation of the Mann Eddy.

Description: Estimating the magnitude of Agulhas leakage, the volume flux of water from the Indian to the Atlantic Ocean, is difficult because of the presence of other circulation systems in the Agulhas region. Indian Ocean water in the Atlantic Ocean is vigorously mixed and diluted in the Cape Basin. Eulerian integration methods, where the velocity field perpendicular to a section is integrated to yield a flux, have to be calibrated so that only the flux by Agulhas leakage is sampled. Two Eulerian methods for estimating the magnitude of Agulhas leakage are tested within a high-resolution two-way nested model with the goal to devise a mooring-based measurement strategy. At the GoodHope line, a section halfway through the Cape Basin, the integrated velocity perpendicular to that line is compared to the magnitude of Agulhas leakage as determined from the transport carried by numerical Lagrangian floats. In the first method, integration is limited to the flux of water warmer and more saline than specific threshold values. These threshold values are determined by maximizing the correlation with the float-determined time series. By using the threshold values, approximately half of the leakage can directly be measured. The total amount of Agulhas leakage can be estimated using a linear regression, within a 90% confidence band of 12 Sv. In the second method, a subregion of the GoodHope line is sought so that integration over that subregion yields an Eulerian flux as close to the float-determined leakage as possible. It appears that when integration is limited within the model to the upper 300 m of the water column within 900 km of the African coast the time series have the smallest root-mean-square difference. This method yields a root-mean-square error of only 5.2 Sv but the 90% confidence band of the estimate is 20 Sv. It is concluded that the optimum thermohaline threshold method leads to more accurate estimates even though the directly measured transport is a factor of two lower than the actual magnitude of Agulhas leakage in this model.

Description: A decade of weak convection in the Labrador Sea associated with decreasing water mass transformation, in combination with advective and eddy fluxes into the convection area, caused significant warming of the deep waters in both the central Labrador Sea and boundary current system along the Labrador shelf break. The connection to the export of Deep Water was studied based on moored current meter stations between 1997 and 2009 at the exit of the Labrador Sea, near the shelf break at 5˚3N. More than 100 year -long current meter records spanning the full water column have been analyzed with respect to high frequency variability, decaying from the surface to the bottom layer, and for the annual mean flow, showing intra- to interannual variability but no detectable decadal trend in the strength of the deep and near-bottom flow out of the Labrador Sea.

Description: Here we present the first radiometric age data and a comprehensive geochemical data set (including major and trace element and Sr–Nd–Pb–Hf isotope ratios) for samples from the Hikurangi Plateau basement and seamounts on and adjacent to the plateau obtained during the R/V Sonne 168 cruise, in addition to age and geochemical data from DSDP Site 317 on the Manihiki Plateau. The 40Ar/39Ar age and geochemical data show that the Hikurangi basement lavas (118–96 Ma) have surprisingly similar major and trace element and isotopic characteristics to the Ontong Java Plateau lavas (ca. 120 and 90 Ma), primarily the Kwaimbaita-type composition, whereas the Manihiki DSDP Site 317 lavas (117 Ma) have similar compositions to the Singgalo lavas on the Ontong Java Plateau. Alkalic, incompatible-element-enriched seamount lavas (99–87 Ma and 67 Ma) on the Hikurangi Plateau and adjacent to it (Kiore Seamount), however, were derived from a distinct high time-integrated U/Pb (HIMU)-type mantle source. The seamount lavas are similar in composition to similar-aged alkalic volcanism on New Zealand, indicating a second wide-spread event from a distinct source beginning ca. 20 Ma after the plateau-forming event. Tholeiitic lavas from two Osbourn seamounts on the abyssal plain adjacent to the northeast Hikurangi Plateau margin have extremely depleted incompatible element compositions, but incompatible element characteristics similar to the Hikurangi and Ontong Java Plateau lavas and enriched isotopic compositions intermediate between normal mid-ocean-ridge basalt (N-MORB) and the plateau basement. These younger (not, vert, similar52 Ma) seamounts may have formed through remelting of mafic cumulate rocks associated with the plateau formation. The similarity in age and geochemistry of the Hikurangi, Ontong Java and Manihiki Plateaus suggest derivation from a common mantle source. We propose that the Greater Ontong Java Event, during which not, vert, similar1% of the Earth’s surface was covered with volcanism, resulted from a thermo-chemical superplume/dome that stalled at the transition zone, similar to but larger than the structure imaged presently beneath the South Pacific superswell. The later alkalic volcanism on the Hikurangi Plateau and the Zealandia micro-continent may have been part of a second large-scale volcanic event that may have also triggered the final breakup stage of Gondwana, which resulted in the separation of Zealandia fragments from West Antarctica.

Description: This study of Antarctic sympagic meiofauna in pack ice during late winter compares communities between the perennially ice-covered western Weddell Sea and the seasonally ice-covered southern Indian Ocean. Sympagic meiofauna (proto- and metazoans 〉20 μm) and eggs 〉20 μm were studied in terms of diversity, abundance and carbon biomass, and with respect to vertical distribution. Metazoan meiofauna had significantly higher abundance and biomass in the western Weddell Sea (medians: 31.1×103 m−2 and 6.53mg m−2, respectively) than in the southern Indian Ocean (medians: 1.0×10 103 m−2and 0.06 mg m−2, respectively). Metazoan diversity was also significantly higher in the western Weddell Sea. Furthermore, the two regions differed significantly in terms of meiofauna community composition, as revealed through multivariate analyses. The overall diversity of sympagic meiofauna was high, and integrated abundance and biomass of total meiofauna were also high in both regions (0.6–178.6×103 m−2 and 0.02–89.70mg m−2, respectively), mostly exceeding values reported earlier from the western Weddell Sea in winter. We attribute the differences in meiofauna communities between the two regions to the older first-year ice and multi-year ice that is present in the western Weddell Sea, but not in the southern Indian Ocean. Our study indicates the significance of perennially ice-covered regions for the establishment of diverse and abundant meiofauna communities. Furthermore, it highlights the potential importance of sympagic meiofauna for the organic matter pool and trophic interactions in sea ice.

Description: We present 40Ar/39Ar age and geochemical (major and trace element and Sr–Nd–Hf–Pb isotope) data from submarine samples recovered from the basement of the Manihiki Plateau during the R/V Sonne research expedition SO193. The samples, predominately tholeiites, with minor occurrences of basaltic andesites and hawaiites, give a mean age of 124.6 ± 1.6 Ma from four different localities on the plateau. Based on TiO2 content, we define two groups of volcanic rocks that differ in trace element and isotopic compositions. Partial melting modeling suggests that the low-Ti group lavas were derived through large degrees of melting (c. 30%) of a peridotitic source at mantle potential melting temperatures of c. Tp = 1510 °C, more than 100 °C above the ambient mantle potential melting temperature. Since the primary water contents of both groups of lavas are low (0.1–0.3g wt.%) and the source is peridotitic, excess temperature is most likely the reason for the large degrees of melting producing the large volume of plateau basalts, consistent with the involvement of a mantle plume. The incompatible element contents of the low-Ti group lavas show a multistage history with enrichment in the most incompatible elements of a previously highly depleted source. They have isotopic compositions similar to enriched mid-ocean-ridge basalt (EMORB) and similar to the common focal zone (FOZO) component. The high-Ti group lavas have more enriched incompatible element compositions overall. Their isotopic compositions tend towards an enriched mantle (EMI)-type endmember, similar, although less extreme, than lavas from the Pitcairn Islands. The geochemistry of the Manihiki Plateau can best be explained by a plume containing three components: 1) a dominant peridotitic FOZO-type component, 2) delaminated EMI-type subcontinental lithospheric mantle (SCLM), and 3) a HIMU (recycled oceanic crustal)-type component possibly in the form of eclogite/pyroxenite. The similarity in age and geochemical composition of Manihiki, Hikurangi and Ontong Java basement lavas, including volcanism in some adjacent basins, suggests that the Greater Ontong Java Volcanic Event covered c. 1% of the Earth's surface with volcanism.

Description: Recent work shows that multichannel seismic (MCS) systems provide detailed information on the oceans' finestructure. The aim of this paper is to analyze if high order numerical algorithms are suitable to accurately model the extremely weak wavefield scattered by the oceans' finestructures. For this purpose, we generate synthetic shot records along a coincident seismic and oceanographic profile acquired across a Mediterranean salt lens in the Gulf of Cadiz. We apply a 2D finite-difference time-domain propagation model, together with second-order Complex Frequency Shifted Perfectly Matched Layers at the numerical boundaries, using as reference a realistic sound speed map with the lateral resolution of the seismic data. We show that our numerical propagator creates an acoustical image of the ocean finestructures including the salt lens that reproduces with outstanding detail the real acquired one

Description: Recently seismic reflection methods have been successfully applied to oceanographic issues. Here, we present a new approach, combining XBT and CTD surveys with seismic observations, to visualize long sections with a resolution down to a few meters. The challenge to a full investigation of mixing processes has been the tremendous span of spatial scales ranging from hundreds of kilometers to centimeters. Traditional hydrographic observations could only resolve the large scale effects by measuring temperature and salinity profiles at discrete locations typically several kilometers apart, whereas dedicated localized measurements allowed investigation of the ocean fine structure at the other end of the spatial spectrum. The intermediate scales have in contrast been difficult to observe systematically. Here we present temperature and salinity data inverted from seismic observations that cover the intermediate scales and provide a new approach to image mesoscale processes and allow the investigation of their dynamics at unprecedented resolution.

Description: Three novel natural products, sorbifuranones A–C (4–6), were isolated from a Penicillium chrysogenum fungus isolated from the marine sponge Ircinia fasciculata. Sorbifuranones B (5) and C (6) and 2′,3′-dihydrosorbicillin, a putative precursor to sorbifuranone B, were also found in the culture of another Penicillium strain, which was isolated from the sponge Tethya aurantium. Their constitutions were elucidated mainly by 2D NMR. NOE correlations in combination with quantum chemical calculations and comparison of experimental and calculated electronic circular dichroism (CD) spectra permitted assignment of the absolute configuration of sorbifuranone C. The structures hint at a two-step cleavage-cyclization sequence of sorbifuranone A (4) leading to the spiro compound sorbifuranone C, while sorbifuranone B is likely to be the respective cleavage product of a putative 2′,3′-dihydrosorbifuranone A, which cannot cyclize further.

Description: The continental slope of the northern Gulf of Mexico seaward of the Mississippi Delta is characterized by very rapid Quaternary sedimentation. Thick sequences of underconsolidated muds and mudstones are present, which are severely overpressured. In the Ursa Basin, Site U1322 of the Integrated Ocean Drilling Program (IODP) provided an excellent coring record of interleaved fine-grained turbidites and hemipelagic sediments, in part severely affected by submarine slumping and sliding after deposition. Cores were continuously sampled and analyzed for anisotropy of magnetic susceptibility (AMS), to elucidate the effects of different transport mechanisms and degree of settling and consolidation on magnetic fabric properties. Generally AMS ellipticity increases with depth irrespective of transport mode, due to loss of porosity. Samples from slumped mass transport deposits (MTD), however, have higher AMS if compared to immediately overlying non-slumped material. MTD samples dominantly show triaxial magnetic fabrics whereas those found in non-slumped sediments are much more oblate. Long axes of the fabric ellipsoid reflect the direction of eastward to southward suspension transport in samples not overprinted by sliding or slumping. Short ellipsoid axes in non-slumped material are vertical, and thus parallel to the axis of maximum uniaxial shortening. In the MTD samples, many short ellipsoid axes are inclined, reflecting an overprint of the uniaxial shortening by bed-parallel shearing induced by the slumping. Shear and MTD transport direction deduced from the fabrics is top-to-SE, downslope along the morphological axis of Ursa Basin. Generally we show that magnetic fabrics of muds and mudstones are sensitive recorders of sedimentary and tectonic processes, and can be used to reconstruct essential parts of basin history.

Description: Marine macroalgae are constantly exposed to epibacterial colonizers. The epiphytic bacterial patterns and their temporal and spatial variability on host algae are poorly understood. To investigate the interaction between marine macroalgae and epiphytic bacteria, this study tested if the composition of epibacterial communities on different macroalgae was specific and persisted under varying biotic and abiotic environmental conditions over a 2-year observation time frame. Epibacterial communities on the co-occurring macroalgae Fucus vesiculosus, Gracilaria vermiculophylla and Ulva intestinalis were repeatedly sampled in summer and winter of 2007 and 2008. The epibacterial community composition was analysed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene libraries. Epibacterial community profiles did not only differ significantly at each sampling interval among algal species, but also showed consistent seasonal differences on each algal species at a bacterial phylum level. These compositional patterns re-occurred at the same season of two consecutive years. Within replicates of the same algal species, the composition of bacterial phyla was subject to shifts at the bacterial species level, both within the same season but at different years and between different seasons. However, 7–16% of sequences were identified as species specific to the host alga. These findings demonstrate that marine macroalgae harbour species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces. Since several algal host-specific bacteria were highly similar to other bacteria known to either avoid subsequent colonization by eukaryotic larvae or to exhibit potent antibacterial activities, algal host-specific bacterial associations are expected to play an important role for marine macroalgae.

Description: A wind-driven meso-scale pattern of temperature, salinity and oxygen was found along a transect in the northern Bornholm Basin (southern Baltic Sea). Strong winds caused currents along this transect, which shifted cold intermediate water (minimum: 3.6C) towards the south. The transect was surveyed with a towed CTD-system and hydroacoustics in parallel to investigate the distribution of sprat, Sprattus sprattus balticus (Schn.) in relation to the observed meso-scale pattern. In those parts of the transect where the cold intermediate water was observed, sprat were restricted to water layers below the halocline. In other parts of the transect, sprat moved into higher water layers and occupied a wider depth range. The important factor was temperature, which set an upper limit to the vertical sprat distribution. The development of hydrography, as measured in the field, was evaluated with a hydrodynamic model.

Description: Thermal tolerance was determined in two closely related amphipod species from contrasting environments (sub-littoral and supra-littoral zones of the sea) using HSP expression and the activity of antioxidant enzymes. The levels of HSP70 and small HSPs present in untreated control animals were higher in the supra-littoral Orchestia gammarellus than in the sub-littoral Gammarus oceanicus. Under the acute thermal stress, HSP levels increased less strongly in O. gammarellus than in G. oceanicus. Activities of antioxidant enzymes peroxidase, catalase and glutathione S-transferase, were more pronounced in the supra-littoral O. gammarellus then in the sub-littoral G. oceanicus. We conclude that the environmental temperature regime modifies key cellular defense mechanisms in amphipods. Higher levels of constitutive HSP synthesis and higher levels of antioxidant enzymes in the supra-littoral species likely reflects adaptation to this highly thermally variable environment.

Description: Nitrogen (N) fixation by specialized microorganisms (diazotrophs) influences global plankton productivity because it provides the ocean with most of its bio-available N. However, its global rate and large-scale spatial distribution is still regarded with considerable uncertainty. Here we use a global ocean nitrogen isotope model, in comparison with δ15NO3− observations, to constrain the pattern of N2 fixation across the Pacific Ocean. N2 fixation introduces isotopically light atmospheric N2 from to the ocean (δ15N = 0‰) relative to the oceanic average near 5‰, which makes nitrogen isotopes suitable to infer patterns of N2 fixation. Including atmospheric iron limitation of diazotrophy in the model shifts the pattern of simulated N2 fixation from the South Pacific to the North Pacific and from the East Pacific westward. These changes considerably improve the agreement with meridional transects of available δ15NO3− observations, as well as excess P (PO43− − NO3−/16), suggesting that atmospheric iron deposition is indeed important for N fixation in the Pacific Ocean. This study highlights the potential for using δ15N observations and model simulations to constrain patterns and rates of N fixation in the ocean.

Description: During the last decade, global surface temperatures did not increase as rapidly as in the preceding decades. Although relatively small compared to the observed centennial scale global warming, it has renewed interest in understanding and even predicting climate on time scales of decades, and sparked a community initiative on near‐term prediction that will feature in the fifth intergovernmental panel on climate change assessment report. Decadal prediction, however, is in its infancy, with only a few publications existing. This article has three aims. The first is to make the case for decadal prediction. Decadal fluctuations in global climate similar to that of recent decades were observed during the past century. Associated with large regional changes in precipitation and climate extremes, they are of socioeconomic importance. Climate models, which capture some aspects of observed decadal variability, indicate that such variations might be partly predictable. The second aim is to describe the major challenges to skilful decadal climate prediction. One is poor understanding of mechanisms of decadal climate variability, with climate models showing little agreement. Sparse observations in the past, particularly in the ocean, are also a limiting factor to developing and testing of initialization and prediction systems. The third aim is to stress that despite promising initial results, decadal prediction is in a highly experimental stage, and care is needed in interpreting results and utilizing data from such experiments. In the long‐term, decadal prediction has the potential to improve models, reduce uncertainties in climate change projections, and be of socioeconomic benefit. Copyright © 2010 John Wiley & Sons, Ltd.

Description: The Atlantic‐Mediterranean exchange of water at Gibraltar represents a significant heat and freshwater sink for the North Atlantic and is a major control on the heat, salt and freshwater budgets of the Mediterranean Sea. Consequently, an understanding of the response of the exchange system to external changes is vital to a full comprehension of the hydrographic responses in both ocean basins. Here, we use a synthesis of empirical (oxygen isotope, planktonic foraminiferal assemblage) and modeling (analytical and general circulation) approaches to investigate the response of the Gibraltar Exchange system to Atlantic freshening during Heinrich Stadials (HSs). HSs display relatively flat W–E surface hydrographic gradients more comparable to the Late Holocene than the Last Glacial Maximum. This is significant, as it implies a similar state of surface circulation during these periods and a different state during the Last Glacial Maximum. During HS1, the gradient may have collapsed altogether, implying very strong water column stratification and a single thermal and d18Owater condition in surface water extending from southern Portugal to the eastern Alboran Sea. Together, these observations imply that inflow of Atlantic water into the Mediterranean was significantly increased during HS periods compared to background glacial conditions. Modeling efforts confirm that this is a predictable consequence of freshening North Atlantic surface water with iceberg meltwater and indicate that the enhanced exchange condition would last until the cessation of anomalous freshwater supply into to the northern North Atlantic. The close coupling of dynamics at Gibraltar Exchange with the Atlantic freshwater system provides an explanation for observations of increased Mediterranean Outflow activity during HS periods and also during the last deglaciation. This coupling is also significant to global ocean dynamics, as it causes density enhancement of the Atlantic water column via the Gibraltar Exchange to be inversely related to North Atlantic surface salinity. Consequently, Mediterranean enhancement of the Atlantic Meridional Overturning Circulation will be greatest when the overturning itself is at its weakest, a potentially critical negative feedback to Atlantic buoyancy change during times of ice sheet collapse.

Description: The stratospheric climate and variability from simulations of sixteen chemistryclimate models is evaluated. On average the polar night jet is well reproduced though its variability is less well reproduced with a large spread between models. Polar temperature biases are less than 5 K except in the Southern Hemisphere (SH) lower stratosphere in spring. The accumulated area of low temperatures responsible for polar stratospheric cloud formation is accurately reproduced for the Antarctic but underestimated for the Arctic. The shape and position of the polar vortex is well simulated, as is the tropical upwelling in the lower stratosphere. There is a wide model spread in the frequency of major sudden stratospheric warnings (SSWs), late biases in the breakup of the SH vortex, and a weak annual cycle in the zonal wind in the tropical upper stratosphere. Quantitatively, “metrics” indicate a wide spread in model performance for most diagnostics with systematic biases in many, and poorer performance in the SH than in the Northern Hemisphere (NH). Correlations were found in the SH between errors in the final warming, polar temperatures, the leading mode of variability, and jet strength, and in the NH between errors in polar temperatures, frequency of major SSWs, and jet strength. Models with a stronger QBO have stronger tropical upwelling and a colder NH vortex. Both the qualitative and quantitative analysis indicate a number of common and long‐standing model problems, particularly related to the simulation of the SH and stratospheric variability.

Description: The phosphorus budget of the pre-human modern ocean is constrained applying the most recent estimates of the natural riverine, eolian, and ice-rafted input fluxes, the phosphorus burial in marine sediments, and the hydrothermal removal of dissolved phosphate from the deep ocean. This review of current flux estimates indicates that the phosphorus budget of the ocean is unbalanced since the accumulation of phosphorus in marine sediments and altered oceanic crust exceeds the continental input of particulate and dissolved phosphorus. The phosphorus mass balance is further tested considering the dissolved phosphate distribution in the deep water column, the marine export production of particulate organic matter, rain rates of phosphorus to the seafloor, benthic dissolved phosphate fluxes, and the organic carbon to phosphorus ratios in marine particles. These independent data confirm that the phosphate and phosphorus budgets were not at steadystate in the pre-human global ocean. The ocean is losing dissolved phosphate at a rate of ≥ 11.6 x 1010 mol yr-1 corresponding to a decline in the phosphate inventory of ≥ 4.5 % kyr-1. Benthic data show that phosphate is preferentially retained in pelagic deep-sea sediments where extended oxygen exposure times favor the degradation of particulate organic matter and the up-take of phosphate in manganese and iron oxides and hydroxides. Enhanced C : P regeneration ratios observed in the deep water column (〉400 m water depth) probably reflect the preferential burial of phosphorus in pelagic sediments. Excess phosphate is released from continental margin sediments deposited in low-oxygen environments. The dissolved oxygen threshold value for the enhanced release of dissolved phosphate is ~20 μM. Benthic phosphate fluxes increase drastically when oxygen concentrations fall below this value.

Description: The decay kinetics of superoxide (O2−) reacting with organic matter was examined in oligotrophic waters at, and nearby, the TENATSO ocean observatory adjacent to the Cape Verde archipelago. Superoxide is the short-lived primary photochemical product of colored dissolved organic matter (CDOM) photolysis and also reacts with CDOM or trace metals (Cu, Fe) to form H2O2. In the present work we focused our investigations on reactions between CDOM and superoxide. O2− decay kinetics experiments were performed by adding KO2 to diethylenetriaminepentaacetic acid (DTPA) amended seawater and utilizing an established chemiluminescence technique for the detection of O2− at nM levels. In Cape Verdean waters we found a significant reactivity of superoxide with CDOM with maximal rates adjacent to the chlorophyll maximum, presumably from production of new CDOM from bacteria/phytoplankton. This work highlights a poorly understood process which impacts on the biogeochemical cycling of CDOM and trace metals in the open ocean.

Description: We present recently-acquired high-resolution seismic data and older lower-resolution seismic data from Rock Garden, a shallow marine gas hydrate province on New Zealand's Hikurangi Margin. The seismic data reveal plumbing systems that supply gas to three general sites where seeps have been observed on the Rock Garden seafloor: the ‘LM3’ sites (including LM3 and LM3-A), the ‘Weka’ sites (including Weka-A, Weka-B, and Weka-C), and the ‘Faure’ sites (including Faure-A, Faure-B, and Rock Garden Knoll). At the LM3 sites, seismic data reveal gas migration from beneath the bottom simulating reflection (BSR), through the gas hydrate stability zone (GHSZ), to two separate seafloor seeps (LM3 and LM3-A). Gas migration through the deeper parts of GHSZ below the LM3 seeps appears to be influenced by faulting in the hanging wall of a major thrust fault. Closer to the seafloor, the dominant migration pathways appear to occupy vertical chimneys. At the Weka sites, on the central part of the ridge, seismic data reveal a very shallow BSR. A distinct convergence of the BSR with the seafloor is observed at the exit point of one of the Weka seep locations (Weka-A). Gas supply to this seep is predicted to be focused along the underside of a permeability contrast at the BGHS caused by overlying gas hydrates. The Faure sites are associated with a prominent arcuate slump feature. At Faure-A, high-amplitude reflections, extending from a shallow BSR towards the seafloor, are interpreted as preferred gas migration pathways that exploit relatively-high-permeability sedimentary layers. At Faure-B, we interpret gas migration to be channelled to the seep along the underside of the BGHS — the same scenario interpreted for the Weka-A site. At Rock Garden Knoll, gas occupies shallow sediments within the GHSZ, and is interpreted to migrate up-dip along relatively high-permeability layers to the area of seafloor seepage. We predict that faulting, in response to uplift and flexural extension of the ridge, may be an important mechanism in creating fluid flow conduits that link the reservoir of free gas beneath the BGHS with the shallow accumulations of gas imaged beneath Rock Garden Knoll. From a more regional perspective, much of the gas beneath Rock Garden is focused along a northwest-dipping fabric, probably associated with subduction-related deformation of the margin.

Description: The southern Hikurangi Subduction Margin is characterized by significant accretion with predicted high rates of fluid expulsion. Bottom simulating reflections (BSRs) are widespread on this margin, predominantly occurring beneath thrust ridges. We present seismic data across the Porangahau Ridge on the outer accretionary wedge. The data show high-amplitude reflections above the regional BSR level. Based on polarity and reflection strength, we interpret these reflections as being caused by free gas. We propose that the presence of gas above the regional level of BSRs indicates local upwarping of the base of gas hydrate stability caused by advective heatflow from upward migrating fluids, although we cannot entirely rule out alternative processes. Simplified modelling of the increase of the thermal gradient associated with fluid flow suggests that funnelling of upward migrating fluids beneath low-permeability slope basins into the Porangahau Ridge would not lead to the pronounced thermal anomaly inferred from upwarping of the base of gas hydrate stability. Focussing of fluid flow is predicted to take place deep in the accretionary wedge and/or the underthrust sediments. Above the high-amplitude reflections, sediment reflectivity is low. A lack of lateral continuity of reflections suggests that reflectivity is lost because of a destruction of sediment layering from deformation rather than gas-hydrate-related amplitude blanking. Structural permeability from fracturing of sediments during deformation may facilitate fluid expulsion on the ridge. A gap in the BSR in the southern part of the study area may be caused by a loss of gas during fluid expulsion. We speculate that gaps in otherwise continuous BSRs that are observed beneath some thrusts on the Hikurangi Margin may be characteristic of other locations experiencing focussed fluid expulsion.

Description: The imbricated frontal wedge of the central Hikurangi subduction margin is characteristic of wide (ca. 150 km), poorly drained and over pressured, low taper (not, vert, similar 4°) thrust systems associated with a relatively smooth subducting plate, a thick trench sedimentary sequence (not, vert, similar 3–4 km), weak basal décollement, and moderate convergence rate (not, vert, similar 40 mm/yr). New seismic reflection and multibeam bathymetric data are used to interpret the regional tectonic structures, and to establish the geological framework for gas hydrates and fluid seeps. We discuss the stratigraphy of the subducting and accreting sequences, characterize stratigraphically the location of the interplate décollement, and describe the deformation of the upper plate thrust wedge together with its cover sequence of Miocene to Recent shelf and slope basin sediments. We identify approximately the contact between an inner foundation of deforming Late Cretaceous and Paleogene rocks, in which widespread out-of-sequence thrusting occurs, and a 65–70 km-wide outer wedge of late Cenozoic accreted turbidites. Although part of a seamount ridge is presently subducting beneath the deformation front at the widest part of the margin, the morphology of the accretionary wedge indicates that frontal accretion there has been largely uninhibited for at least 1–2 Myr. This differs from the offshore Hawkes Bay sector of the margin to the north where a substantial seamount with up to 3 km of relief has been subducted beneath the lower margin, resulting in uplift and complex deformation of the lower slope, and a narrow (10–20 km) active frontal wedge. Five areas with multiple fluid seep sites, referred to informally as Wairarapa, Uruti Ridge, Omakere Ridge, Rock Garden, and Builders Pencil, typically lie in 700–1200 m water depth on the crests of thrust-faulted, anticlinal ridges along the mid-slope. Uruti Ridge sites also lie in close proximity to the eastern end of a major strike-slip fault. Rock Garden sites lie directly above a subducting seamount. Structural permeability is inferred to be important at all levels of the thrust system. There is a clear relationship between the seeps and major seaward-vergent thrust faults, near the outer edge of the deforming Cretaceous and Paleogene inner foundation rocks. This indicates that thrust faults are primary fluid conduits and that poor permeability of the Cretaceous and Paleogene inner foundation focuses fluid flow to its outer edge. The sources of fluids expelling at active seep sites along the middle slope may include the inner parts of the thrust wedge and subducting sediments below the décollement. Within anticlinal ridges beneath the active seep sites there is a conspicuous break in the bottom simulating reflector (BSR), and commonly a seismically-resolvable shallow fault network through which fluids and gas percolate to the seafloor. No active fluid venting has yet been recognized over the frontal accretionary wedge, but the presence of a widespread BSR, an extensive protothrust zone (〉 200 km by 20 km) in the Hikurangi Trough, and two unconfirmed sites of possible previous fluid expulsion, suggest that the frontal wedge could be actively dewatering. There are presently no constraints on the relative fluid flux between the frontal wedge and the active mid-slope fluid seeps. Article Outline

Description: Understanding the upward motion of CO2 droplets or CH4 bubbles in oceanic waters is prerequisite to predict the vertical distribution of the two most important greenhouse gases in the water column after these have been released from the seabed. One of the key parameters governing the fate of droplets or bubbles dissolving into the surrounding seawater as they rise, is the terminal velocity, uT. The latter is strongly influenced by the ability of both compounds to form skins of gas hydrate, if pressure and temperature satisfy thermodynamic framework conditions. Experimental efforts aiming to elucidate the rise properties of CO2 droplets and CH4 bubbles and specifically the influence of hydrate skins open the possibility to obtain a parameterization of uT applicable to both hydrate-coated and pure fluid particles of CH4 and CO2. With the present study, we report on experimentally determined terminal velocities of single CH4 bubbles released to pressurized and temperature-regulated seawater. Hydrate skins were identified by high bubble sphericities and changed motion characteristics. Based on these experiments as well as published data on the rise of hydrate-coated and pure liquid CO2 droplets and physical principles previously successfully used for clean bubbles near atmospheric pressures, a new parameterization of uT is proposed. Model predictions show a good agreement with the data base established from the laboratory-based measurements.

Description: Highly concentrated gas hydrate deposits are likely to be associated with geological features that promote increased fluid flux through the gas hydrate stability zone (GHSZ). We conduct conventional seismic processing techniques and full-waveform inversion methods on a multi-channel seismic line that was acquired over a 125 km transect of the southern Hikurangi Margin off the eastern coast of New Zealand’s North Island. Initial processing, employed with an emphasis on preservation of true amplitude information, was used to identify three sites where structures and stratal fabrics likely encourage focused fluid flow into and through the GHSZ. At two of the sites, Western Porangahau Trough and Eastern Porangahau Ridge, sub-vertical blanking zones occur in regions of intensely deformed sedimentary layering. It is interpreted that increased fluid flow occurs in these regions and that fluids may dissipate upwards and away from the deformed zone along layers that trend towards the seafloor. At Eastern Porangahau Ridge we also observe a coherent bottom simulating reflection (BSR) that increases markedly in intensity with proximity to the centre of the anticlinal ridge. 1D full-waveform inversions conducted at eight points along the BSR reveal much more pronounced low-velocity zones near the centre of the ridge, indicating a local increase in the flux of gas-charged fluids into the anticline. At another anticline, Western Porangahau Ridge, a dipping high-amplitude feature extends from the BSR upwards towards the seafloor within the regional GHSZ. 1D full-waveform inversions at this site reveal that the dipping feature is characterised by a high-velocity zone overlying a low-velocity zone, which we interpret as gas hydrates overlying free gas. These results support a previous interpretation that this high-amplitude feature represents a local “up-warping” of the base of hydrate stability in response to advective heat flow from upward migrating fluids. These three sites provide examples of geological frameworks that encourage prolific localised fluid flow into the hydrate system where it is likely that gas-charged fluids are converting to highly concentrated hydrate deposits.

Description: A dynamic model has been developed to represent biogeochemical variables and processes observed during experimental blooms of the coccolithophore Emiliania huxleyi induced in mesocosms over a period of 23 days. The model describes carbon (C), nitrogen (N), and phosphorus (P) cycling through E. huxleyi and the microbial loop, and computes pH and the partial pressure of carbon dioxide (pCO2) from dissolved inorganic carbon (DIC) and total alkalinity (TA). The main innovations are: 1) the representation of E. huxleyi dynamics using an unbalanced growth model in carbon and nitrogen, 2) the gathering of formulations describing typical processes involved in the export of carbon such as primary production, calcification, cellular dissolved organic carbon (DOC) excretion, transparent exopolymer (TEP) formation and viral lyses, and 3) an original and validated representation of the calcification process as a function of the net primary production with a modulation by the intra-cellular N:C ratio mimicking the effect of nutrients limitation on the onset of calcification. It is shown that this new mathematical formulation of calcification provides a better representation of the dynamics of TA, DIC and calcification rates derived from experimental data compared to classicaly used formulations (e.g. function of biomass or of net primary production without any modulation term). In a first step, the model has been applied to the simulations of present pCO2 conditions. It adequately reproduces the observations for chemical and biological variables and provides an overall view of carbon and nitrogen dynamics. Carbon and nitrogen budgets are derived from the model for the different phases of the bloom, highlighting three distinct phases, reflecting the evolution of the cellular C:N ratio and the interaction between hosts and viruses. During the first phase, inorganic nutrients are massively consumed by E. huxleyi increasing its biomass. Uptakes of carbon and nitrogen are maintained at a constant ratio. The second phase is triggered by the exhaustion of phosphate (PO43−). Uptake of carbon and nitrogen being uncoupled, the cellular C:N ratio of E. huxleyi increases. This stimulates the active release of DOC, acting as precursors for TEP. The third phase is characterised by an enhancement of the phytoplankton mortality due to viral lysis. A huge amount of DOC has been accumulated in the mesocosm. Research highlights ► Unbalanced growth model in carbon and nitrogen applied to E.Huxleyi dynamics. ► Gathering of formulations describing typical processes involved in export of carbon. ► Original representation of calcification as a function of primary production. ► Explicit representation of enhanced mortality linked to viral lysis.