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  • Authors: Bach, L. T.; Stange, P.; Taucher, J.; Achterberg, E. P.; +4 Authors

    Gravitational sinking of photosynthetically fixed particulate organic carbon (POC) constitutes a key component of the biological carbon pump. The fraction of POC leaving the surface ocean depends on POC sinking velocity (SV) and remineralization rate (Cremin), both of which depend on plankton community structure. However, the key drivers in plankton communities controlling SV and Cremin are poorly constrained. In fall 2014, we conducted a 6-week mesocosm experiment in the subtropical NE Atlantic Ocean to study the influence of plankton community structure on SV and Cremin. Oligotrophic conditions prevailed for the first 3 weeks, until nutrient-rich deep water injected into all mesocosms stimulated diatom blooms. SV declined steadily over the course of the experiment due to decreasing CaCO3 ballast and—according to an optical proxy proposed herein—due to increasing aggregate porosity mostly during an aggregation event after the diatom bloom. Furthermore, SV was positively correlated with the contribution of picophytoplankton to the total phytoplankton biomass. Cremin was highest during a Synechococcus bloom under oligotrophic conditions and in some mesocosms during the diatom bloom after the deep water addition, while it was particularly low during harmful algal blooms. The temporal changes were considerably larger in Cremin (max. fifteenfold) than in SV (max. threefold). Accordingly, estimated POC transfer efficiency to 1,000 m was mainly dependent on how the plankton community structure affected Cremin. Our approach revealed key players and interactions in the plankton food web influencing POC export efficiency thereby improving our mechanistic understanding of the biological carbon pump.

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  • Authors: Grosse-Brauckmann, Gisbert;

    Für den Abschnitt "Torfe" der Bodenkundlichen Kartieranleitung, deren 4. Auflage zur Zeit vorbereitet wird, wurde ein neuer Textvorschlag erarbeitet, der hiermit vorgelegt wird. Behandelt werden darin 1) die unterschiedlichen Klassifikationsmöglichkeiten der Torfe auf "botanischer" Grundlage (in den Torfen vertretene Pflanzenreste) sowie im Hinblick auf (primäre) bodenkundlich-chemische Eigenschaften (Basen- und pH-Verhältnisse), 2) die wichtigsten im Gelände ansprechbaren Pflanzenreste und ihre Merkmale, 3) die Zuordnung von verbreiteten botanisch charakterisierten Torfarten (oder "Torfarteneinheiten") zu den bodenkundlichen "Torfartengruppen" Hoch-, Übergangs- und Niedermoortorf an Hand einer Tabelle. Das entscheidende Kriterium für die Zuordnung zum Hochmoortorf ist das ausschließliche Vorkommen der Reste von Hochmoorpflanzen (diese werden im einzelnen aufgeführt). Übergangsmoortorfe sind durch die Reste von Pflanzenarten ausgezeichnet, die an basen- und nährstoffärmere Standorte außerhalb von Hochmooren gebunden sind (neben ihnen können aber auch Hochmoorpflanzen-Reste vertreten sein). Niedermoortorfe sind charakterisiert durch Reste basen- und nährstoffanspruchsvoller Arten (neben denen auch Reste anspruchsloserer Arten vertreten sein können). Proposals are given for a new text of the section "Peat" of the German Soil Mapping Instruction, the 4th edition of which is now under preparation. The topics dealt with are as follows: 1. The different possibilities of classification of peat: on "botanical" basis (their contents of plant remains) and with respect to (primary) chemico-pedological characteristics (base and pH conditions). 2. The characteristics of the most common plant remains identifiable in the field. 3. The assignment of widespread botanical peat types to the three pedological peat groups: raised-bog peat, transitional-mire peat, and fen peat (shown by a table). The criterion decisive on the assignment of a given peat to raised-bog peat is the exclusive occurrence of remains of raised-bog plants (these are quoted in detail). Transitional-mire peats are distinguished by remains of plant species, which are restricted to sites poor in bases and nutrients (beyond the raised bogs, however), besides of them also raised-bog plant remains may be present. Fen peats are characterized by remains of base and nutrient demanding species (besides of them also remains of plants of poorer sites, but not of raised bogs may be present). DFG, SUB Göttingen research

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  • Authors: Gossler, Manuel A.; Bayer, Peter; Rau, Gabriel C.; Einsiedl, Florian; +1 Authors

    Heat transport in natural porous media, such as aquifers or streambeds, is generally modeled assuming local thermal equilibrium (LTE) between the fluid and solid phases. Yet, the mathematical and hydrogeological conditions and implications of this simplification have not been fully established for natural porous media. To quantify the occurrence and effects of local thermal disequilibrium during heat transport, we systematically compared thermal breakthrough curves from a LTE with those calculated using a local thermal nonequilibrium (LTNE) model, explicitly allowing for different temperatures in the fluid and solid phases. For the LTNE model, we developed a new correlation for the heat transfer coefficient representative of the conditions in natural porous aquifers using six published experimental results. By conducting an extensive parameter study (>50,000 simulations), we show that LTNE effects do not occur for grain sizes smaller than 7 mm or for groundwater flow velocities that are slower than 1.6 m day−1. The limits of LTE are likely exceeded in gravel aquifers or in the vicinity of pumped bores. For such aquifers, the use of a LTE model can lead to an underestimation of the effective thermal dispersion by a factor of up to 30 or higher, while the advective thermal velocity remains unaffected for most conditions. Based on a regression analysis of the simulation results, we provide a criterion which can be used to determine if LTNE effects are expected for particular conditions.

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  • Authors: van der Linden, Roderick; Knippertz, Peter; Fink, Andreas H.; Ingleby, Bruce; +2 Authors

    During the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) field campaign ∼900 radiosondes were launched from 12 stations in southern West Africa from 15 June to 31 July 2016. Subsequently, data-denial experiments were conducted using the Integrated Forecasting System of the European Centre for Medium-range Weather Forecasts (ECMWF) to assess the radiosondes' impact on the quality of analyses and forecasts. As observational reference, satellite-based estimates of rainfall and outgoing long-wave radiation (OLR) as well as the radiosonde measurements themselves are used. With regard to the analyses, the additional observations show positive impacts on winds throughout the troposphere and lower stratosphere, while large lower-tropospheric cold and dry biases are hardly reduced. Nonetheless, downstream, that is farther inland from the radiosonde stations, we find a significant increase (decrease) in low-level night-time temperatures (monsoon winds) when incorporating the DACCIWA observations, suggesting a possible linkage via weaker cold air advection from the Gulf of Guinea. The associated lower relative humidity leads to reduced cloud cover in the DACCIWA analysis. Closer to the coast and over Benin and Togo, DACCIWA observations increase low-level specific humidity and precipitable water, possibly due to changes in advection and vertical mixing. During daytime, differences between the two analyses are generally smaller at low levels. With regard to the forecasts, the impact of the additional observations is lost after a day or less. Moderate improvements occur in low-level wind and temperature but also in rainfall over the downstream Sahel, while impacts on OLR are ambiguous. The changes in precipitation appear to also affect high-level cloud cover and the tropical easterly jet. The overall rather small observation impact suggests that model and data assimilation deficits are the main limiting factors for better forecasts in West Africa. The new observations and physical understanding from DACCIWA can hopefully contribute to reducing these issues.

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  • Authors: Janout, Markus A.; Hellmer, Hartmut H.; Hattermann, Tore; Huhn, Oliver; +6 Authors

    The Filchner‐Ronne Ice Shelf (FRIS) is characterized by moderate basal melt rates due to the near‐freezing waters that dominate the wide southern Weddell Sea continental shelf. We revisited the region in austral summer 2018 with detailed hydrographic and noble gas surveys along FRIS. The FRIS front was characterized by High Salinity Shelf Water (HSSW) in Ronne Depression, Ice Shelf Water (ISW) on its eastern flank, and an inflow of modified Warm Deep Water (mWDW) entering through Central Trough. Filchner Trough was dominated by Ronne HSSW‐sourced ISW, likely forced by a recently intensified circulation beneath FRIS due to enhanced sea ice production in the Ronne polynya since 2015. Glacial meltwater fractions and tracer‐based water mass dating indicate two separate ISW outflow cores, one hugging the Berkner slope after a two‐year travel time, and the other located in the central Filchner Trough following a ∼six year‐long transit through the FRIS cavity. Historical measurements indicate the presence of two distinct modes, in which water masses in Filchner Trough were dominated by either Ronne HSSW‐derived ISW (Ronne‐mode) or more locally derived Berkner‐HSSW (Berkner‐mode). While the dominance of these modes has alternated on interannual time scales, ocean densities in Filchner Trough have remained remarkably stable since the first surveys in 1980. Indeed, geostrophic velocities indicated outflowing ISW‐cores along the trough's western flank and onto Berkner Bank, which suggests that Ronne‐ISW preconditions Berkner‐HSSW production. The negligible density difference between Berkner‐ and Ronne‐mode waters indicates that each contributes cold dense shelf waters to protect FRIS against inflowing mWDW. Plain Language Summary: We visited the largest floating Antarctic ice shelf in the southern Weddell Sea in 2018 with an icebreaker expedition, and measured ocean temperature, salinity, meltwater content, and other parameters in front of the FRIS. We found that the ocean conditions were still dominated by the very cold and dense waters needed to protect the ice shelf from inflowing warm waters from the deep ocean. We compared the 2018 conditions with earlier surveys since the 1980s and concluded that, in spite of climate change and in contrast to other Antarctic regions, the water masses on the southern Weddell Sea shelf remained relatively stable overall. We found that most of the stations we visited near the Filchner Ice Shelf edge were dominated by cold ISW, which forms when water masses interact with the underside of the shelf ice. Our measurements helped improve our understanding regarding the currents and water masses on the southern Weddell Sea continental shelf. Key Points: Hydrographic status update with the first comprehensive CTD survey along the entire FRIS front since 1995. Strong and stable presence of High Salinity Shelf Water in Ronne Depression over decades. Dominance of Ronne‐sourced Ice Shelf Water in Filchner Trough in 2018 points to intensified sub‐FRIS circulation. Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) http://dx.doi.org/10.13039/501100003207

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  • Authors: Roberts, Stephen J.; Monien, Patrick; Foster, Louise C.; Loftfield, Julia; +14 Authors

    Changes in penguin populations on the Antarctic Peninsula have been linked to several environmental factors, but the potentially devastating impact of volcanic activity has not been considered. Here we use detailed biogeochemical analyses to track past penguin colony change over the last 8,500 years on Ardley Island, home to one of the Antarctic Peninsula’s largest breeding populations of gentoo penguins. The first sustained penguin colony was established on Ardley Island c. 6,700 years ago, pre-dating sub-fossil evidence of Peninsula- wide occupation by c. 1,000 years. The colony experienced five population maxima during the Holocene. Overall, we find no consistent relationships with local-regional atmospheric and ocean temperatures or sea-ice conditions, although the colony population maximum, c. 4,000–3,000 years ago, corresponds with regionally elevated temperatures. Instead, at least three of the five phases of penguin colony expansion were abruptly ended by large eruptions from the Deception Island volcano, resulting in near-complete local extinction of the colony, with, on average, 400–800 years required for sustainable recovery. https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3086_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3080_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3081_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3082_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3084_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3085_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3083_ESM.xlsx research

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  • Authors: Tanneberger, Franziska; Appulo, Lea; Ewert, Stefan; Lakner, Sebastian; +3 Authors

    Peatlands are lands with a peat layer at the surface, containing a large proportion of organic carbon. Such lands cover ≈1 000 000 km2 in Europe, which is almost 10% of the total surface area. In many countries, peatlands have been artificially drained over centuries, leading to not only enormous emissions of CO2 but also soil subsidence, mobilization of nutrients, higher flood risks, and loss of biodiversity. These problems can largely be solved by stopping drainage and rewetting the land. Wet peatlands do not release CO2, can potentially sequester carbon, help to improve water quality, provide habitat for rare and threatened biodiversity, and can still be used for production of biomass (“paludiculture”). Wisely adjusted land use on peatlands can substantially contribute to low-emission goals and further benefits for farmers, the economy, society, and the environment.

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  • Authors: Rae, Auriol S. P.; Kenkmann, Thomas; Padmanabha, Vivek; Poelchau, Michael H.; +1 Authors

    Brittle deformation in rocks depends upon loading rate; with increasing rates, typically greater than ~102 s−1, rocks become significantly stronger and undergo increasingly severe fragmentation. Dynamic conditions required for rate-dependent brittle failure may be reached during impact events, seismogenic rupture, and landslides. Material characteristics and fragment characterization of specific geomaterials from dynamic loading are only approximately known. Here we determine the characteristic strain rate for dynamic behavior in felsic crystalline rocks, including anisotropy, and describe the resulting fragments. Regardless of the type of felsic crystalline rock or anisotropy, the characteristic strain rate is the same within uncertainties for all tested materials, with an average value of 229 ± 81 s−1. Despite the lack of variation of the critical strain rate with lithology, we find that the degree of fragmentation as a function of strain rate varies depending on material. Scaled or not, the fragmentation results are inconsistent with current theoretical models of fragmentation. Additionally, we demonstrate that conditions during impact cratering, where the impactor diameter is less than ~100 m, are analogous to the experiments carried out here and therefore that dynamic strengthening and compressive fragmentation should be considered as important processes during impact cratering.

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  • Authors: Matern, Katrin; Weigand, Harald; Kretzschmar, Ruben; Mansfeldt, Tim;

    Chromite ore processing residue (COPR) is a waste derived from the chromate extraction from roasted ores and is deposited in some countries in landfills. The objective of this study was to investigate the leaching characteristics of hexavalent Cr [Cr(VI)] from two COPR samples obtained from unlined landfills in the Kanpur area of northern India. Column experiments were conducted under water-saturated conditions to simulate Cr release from the wastes caused by tropical heavy-rain events. Leached Cr(VI) decreased from 1,800 to 300 mg L−1 (Rania site) and 1,200 to 163 mg L−1 (Chhiwali site) during exchange of 12 pore volumes, which approximately corresponds to 2 yr of monsoon precipitation. Flow interruptions for 10, 100, and 1,000 h had little effect on Cr(VI) concentrations in the leachate, suggesting that Cr(VI) leaching was not limited by slow release kinetics. Calcium aluminum chromium oxide hydrates (CAC), and highly soluble phases such as Na2CrO4 may play a role in controlling Cr(VI) concentration in the leachates. The amount of Cr(VI) leached from the columns accounted for 16% of the total Cr(VI) present in both COPR samples. A decrease in the solid-phase Cr(VI)/Crtotal ratio along the column was identified by X-ray absorption near edge structure (XANES) spectroscopy. Consistently, the smallest Cr(VI)/Crtotal ratios were found in the lower column section closest to the inflow. Our results suggest that Cr(VI) leaching from the unlined COPR landfills will continue for centuries, highlighting the urgent need to remediate these dumpsites.

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  • Authors: Bach, L. T.; Stange, P.; Taucher, J.; Achterberg, E. P.; +4 Authors

    Gravitational sinking of photosynthetically fixed particulate organic carbon (POC) constitutes a key component of the biological carbon pump. The fraction of POC leaving the surface ocean depends on POC sinking velocity (SV) and remineralization rate (Cremin), both of which depend on plankton community structure. However, the key drivers in plankton communities controlling SV and Cremin are poorly constrained. In fall 2014, we conducted a 6-week mesocosm experiment in the subtropical NE Atlantic Ocean to study the influence of plankton community structure on SV and Cremin. Oligotrophic conditions prevailed for the first 3 weeks, until nutrient-rich deep water injected into all mesocosms stimulated diatom blooms. SV declined steadily over the course of the experiment due to decreasing CaCO3 ballast and—according to an optical proxy proposed herein—due to increasing aggregate porosity mostly during an aggregation event after the diatom bloom. Furthermore, SV was positively correlated with the contribution of picophytoplankton to the total phytoplankton biomass. Cremin was highest during a Synechococcus bloom under oligotrophic conditions and in some mesocosms during the diatom bloom after the deep water addition, while it was particularly low during harmful algal blooms. The temporal changes were considerably larger in Cremin (max. fifteenfold) than in SV (max. threefold). Accordingly, estimated POC transfer efficiency to 1,000 m was mainly dependent on how the plankton community structure affected Cremin. Our approach revealed key players and interactions in the plankton food web influencing POC export efficiency thereby improving our mechanistic understanding of the biological carbon pump.

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  • Authors: Grosse-Brauckmann, Gisbert;

    Für den Abschnitt "Torfe" der Bodenkundlichen Kartieranleitung, deren 4. Auflage zur Zeit vorbereitet wird, wurde ein neuer Textvorschlag erarbeitet, der hiermit vorgelegt wird. Behandelt werden darin 1) die unterschiedlichen Klassifikationsmöglichkeiten der Torfe auf "botanischer" Grundlage (in den Torfen vertretene Pflanzenreste) sowie im Hinblick auf (primäre) bodenkundlich-chemische Eigenschaften (Basen- und pH-Verhältnisse), 2) die wichtigsten im Gelände ansprechbaren Pflanzenreste und ihre Merkmale, 3) die Zuordnung von verbreiteten botanisch charakterisierten Torfarten (oder "Torfarteneinheiten") zu den bodenkundlichen "Torfartengruppen" Hoch-, Übergangs- und Niedermoortorf an Hand einer Tabelle. Das entscheidende Kriterium für die Zuordnung zum Hochmoortorf ist das ausschließliche Vorkommen der Reste von Hochmoorpflanzen (diese werden im einzelnen aufgeführt). Übergangsmoortorfe sind durch die Reste von Pflanzenarten ausgezeichnet, die an basen- und nährstoffärmere Standorte außerhalb von Hochmooren gebunden sind (neben ihnen können aber auch Hochmoorpflanzen-Reste vertreten sein). Niedermoortorfe sind charakterisiert durch Reste basen- und nährstoffanspruchsvoller Arten (neben denen auch Reste anspruchsloserer Arten vertreten sein können). Proposals are given for a new text of the section "Peat" of the German Soil Mapping Instruction, the 4th edition of which is now under preparation. The topics dealt with are as follows: 1. The different possibilities of classification of peat: on "botanical" basis (their contents of plant remains) and with respect to (primary) chemico-pedological characteristics (base and pH conditions). 2. The characteristics of the most common plant remains identifiable in the field. 3. The assignment of widespread botanical peat types to the three pedological peat groups: raised-bog peat, transitional-mire peat, and fen peat (shown by a table). The criterion decisive on the assignment of a given peat to raised-bog peat is the exclusive occurrence of remains of raised-bog plants (these are quoted in detail). Transitional-mire peats are distinguished by remains of plant species, which are restricted to sites poor in bases and nutrients (beyond the raised bogs, however), besides of them also raised-bog plant remains may be present. Fen peats are characterized by remains of base and nutrient demanding species (besides of them also remains of plants of poorer sites, but not of raised bogs may be present). DFG, SUB Göttingen research

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  • Authors: Gossler, Manuel A.; Bayer, Peter; Rau, Gabriel C.; Einsiedl, Florian; +1 Authors

    Heat transport in natural porous media, such as aquifers or streambeds, is generally modeled assuming local thermal equilibrium (LTE) between the fluid and solid phases. Yet, the mathematical and hydrogeological conditions and implications of this simplification have not been fully established for natural porous media. To quantify the occurrence and effects of local thermal disequilibrium during heat transport, we systematically compared thermal breakthrough curves from a LTE with those calculated using a local thermal nonequilibrium (LTNE) model, explicitly allowing for different temperatures in the fluid and solid phases. For the LTNE model, we developed a new correlation for the heat transfer coefficient representative of the conditions in natural porous aquifers using six published experimental results. By conducting an extensive parameter study (>50,000 simulations), we show that LTNE effects do not occur for grain sizes smaller than 7 mm or for groundwater flow velocities that are slower than 1.6 m day−1. The limits of LTE are likely exceeded in gravel aquifers or in the vicinity of pumped bores. For such aquifers, the use of a LTE model can lead to an underestimation of the effective thermal dispersion by a factor of up to 30 or higher, while the advective thermal velocity remains unaffected for most conditions. Based on a regression analysis of the simulation results, we provide a criterion which can be used to determine if LTNE effects are expected for particular conditions.

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  • Authors: van der Linden, Roderick; Knippertz, Peter; Fink, Andreas H.; Ingleby, Bruce; +2 Authors

    During the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) field campaign ∼900 radiosondes were launched from 12 stations in southern West Africa from 15 June to 31 July 2016. Subsequently, data-denial experiments were conducted using the Integrated Forecasting System of the European Centre for Medium-range Weather Forecasts (ECMWF) to assess the radiosondes' impact on the quality of analyses and forecasts. As observational reference, satellite-based estimates of rainfall and outgoing long-wave radiation (OLR) as well as the radiosonde measurements themselves are used. With regard to the analyses, the additional observations show positive impacts on winds throughout the troposphere and lower stratosphere, while large lower-tropospheric cold and dry biases are hardly reduced. Nonetheless, downstream, that is farther inland from the radiosonde stations, we find a significant increase (decrease) in low-level night-time temperatures (monsoon winds) when incorporating the DACCIWA observations, suggesting a possible linkage via weaker cold air advection from the Gulf of Guinea. The associated lower relative humidity leads to reduced cloud cover in the DACCIWA analysis. Closer to the coast and over Benin and Togo, DACCIWA observations increase low-level specific humidity and precipitable water, possibly due to changes in advection and vertical mixing. During daytime, differences between the two analyses are generally smaller at low levels. With regard to the forecasts, the impact of the additional observations is lost after a day or less. Moderate improvements occur in low-level wind and temperature but also in rainfall over the downstream Sahel, while impacts on OLR are ambiguous. The changes in precipitation appear to also affect high-level cloud cover and the tropical easterly jet. The overall rather small observation impact suggests that model and data assimilation deficits are the main limiting factors for better forecasts in West Africa. The new observations and physical understanding from DACCIWA can hopefully contribute to reducing these issues.

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  • Authors: Janout, Markus A.; Hellmer, Hartmut H.; Hattermann, Tore; Huhn, Oliver; +6 Authors

    The Filchner‐Ronne Ice Shelf (FRIS) is characterized by moderate basal melt rates due to the near‐freezing waters that dominate the wide southern Weddell Sea continental shelf. We revisited the region in austral summer 2018 with detailed hydrographic and noble gas surveys along FRIS. The FRIS front was characterized by High Salinity Shelf Water (HSSW) in Ronne Depression, Ice Shelf Water (ISW) on its eastern flank, and an inflow of modified Warm Deep Water (mWDW) entering through Central Trough. Filchner Trough was dominated by Ronne HSSW‐sourced ISW, likely forced by a recently intensified circulation beneath FRIS due to enhanced sea ice production in the Ronne polynya since 2015. Glacial meltwater fractions and tracer‐based water mass dating indicate two separate ISW outflow cores, one hugging the Berkner slope after a two‐year travel time, and the other located in the central Filchner Trough following a ∼six year‐long transit through the FRIS cavity. Historical measurements indicate the presence of two distinct modes, in which water masses in Filchner Trough were dominated by either Ronne HSSW‐derived ISW (Ronne‐mode) or more locally derived Berkner‐HSSW (Berkner‐mode). While the dominance of these modes has alternated on interannual time scales, ocean densities in Filchner Trough have remained remarkably stable since the first surveys in 1980. Indeed, geostrophic velocities indicated outflowing ISW‐cores along the trough's western flank and onto Berkner Bank, which suggests that Ronne‐ISW preconditions Berkner‐HSSW production. The negligible density difference between Berkner‐ and Ronne‐mode waters indicates that each contributes cold dense shelf waters to protect FRIS against inflowing mWDW. Plain Language Summary: We visited the largest floating Antarctic ice shelf in the southern Weddell Sea in 2018 with an icebreaker expedition, and measured ocean temperature, salinity, meltwater content, and other parameters in front of the FRIS. We found that the ocean conditions were still dominated by the very cold and dense waters needed to protect the ice shelf from inflowing warm waters from the deep ocean. We compared the 2018 conditions with earlier surveys since the 1980s and concluded that, in spite of climate change and in contrast to other Antarctic regions, the water masses on the southern Weddell Sea shelf remained relatively stable overall. We found that most of the stations we visited near the Filchner Ice Shelf edge were dominated by cold ISW, which forms when water masses interact with the underside of the shelf ice. Our measurements helped improve our understanding regarding the currents and water masses on the southern Weddell Sea continental shelf. Key Points: Hydrographic status update with the first comprehensive CTD survey along the entire FRIS front since 1995. Strong and stable presence of High Salinity Shelf Water in Ronne Depression over decades. Dominance of Ronne‐sourced Ice Shelf Water in Filchner Trough in 2018 points to intensified sub‐FRIS circulation. Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) http://dx.doi.org/10.13039/501100003207

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  • Authors: Roberts, Stephen J.; Monien, Patrick; Foster, Louise C.; Loftfield, Julia; +14 Authors

    Changes in penguin populations on the Antarctic Peninsula have been linked to several environmental factors, but the potentially devastating impact of volcanic activity has not been considered. Here we use detailed biogeochemical analyses to track past penguin colony change over the last 8,500 years on Ardley Island, home to one of the Antarctic Peninsula’s largest breeding populations of gentoo penguins. The first sustained penguin colony was established on Ardley Island c. 6,700 years ago, pre-dating sub-fossil evidence of Peninsula- wide occupation by c. 1,000 years. The colony experienced five population maxima during the Holocene. Overall, we find no consistent relationships with local-regional atmospheric and ocean temperatures or sea-ice conditions, although the colony population maximum, c. 4,000–3,000 years ago, corresponds with regionally elevated temperatures. Instead, at least three of the five phases of penguin colony expansion were abruptly ended by large eruptions from the Deception Island volcano, resulting in near-complete local extinction of the colony, with, on average, 400–800 years required for sustainable recovery. https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3086_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3080_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3081_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3082_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3084_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3085_ESM.xlsx https://static-content.springer.com/esm/art%3A10.1038%2Fncomms14914/MediaObjects/41467_2017_BFncomms14914_MOESM3083_ESM.xlsx research

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  • Authors: Tanneberger, Franziska; Appulo, Lea; Ewert, Stefan; Lakner, Sebastian; +3 Authors

    Peatlands are lands with a peat layer at the surface, containing a large proportion of organic carbon. Such lands cover ≈1 000 000 km2 in Europe, which is almost 10% of the total surface area. In many countries, peatlands have been artificially drained over centuries, leading to not only enormous emissions of CO2 but also soil subsidence, mobilization of nutrients, higher flood risks, and loss of biodiversity. These problems can largely be solved by stopping drainage and rewetting the land. Wet peatlands do not release CO2, can potentially sequester carbon, help to improve water quality, provide habitat for rare and threatened biodiversity, and can still be used for production of biomass (“paludiculture”). Wisely adjusted land use on peatlands can substantially contribute to low-emission goals and further benefits for farmers, the economy, society, and the environment.

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  • Authors: Rae, Auriol S. P.; Kenkmann, Thomas; Padmanabha, Vivek; Poelchau, Michael H.; +1 Authors

    Brittle deformation in rocks depends upon loading rate; with increasing rates, typically greater than ~102 s−1, rocks become significantly stronger and undergo increasingly severe fragmentation. Dynamic conditions required for rate-dependent brittle failure may be reached during impact events, seismogenic rupture, and landslides. Material characteristics and fragment characterization of specific geomaterials from dynamic loading are only approximately known. Here we determine the characteristic strain rate for dynamic behavior in felsic crystalline rocks, including anisotropy, and describe the resulting fragments. Regardless of the type of felsic crystalline rock or anisotropy, the characteristic strain rate is the same within uncertainties for all tested materials, with an average value of 229 ± 81 s−1. Despite the lack of variation of the critical strain rate with lithology, we find that the degree of fragmentation as a function of strain rate varies depending on material. Scaled or not, the fragmentation results are inconsistent with current theoretical models of fragmentation. Additionally, we demonstrate that conditions during impact cratering, where the impactor diameter is less than ~100 m, are analogous to the experiments carried out here and therefore that dynamic strengthening and compressive fragmentation should be considered as important processes during impact cratering.

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  • Authors: Matern, Katrin; Weigand, Harald; Kretzschmar, Ruben; Mansfeldt, Tim;

    Chromite ore processing residue (COPR) is a waste derived from the chromate extraction from roasted ores and is deposited in some countries in landfills. The objective of this study was to investigate the leaching characteristics of hexavalent Cr [Cr(VI)] from two COPR samples obtained from unlined landfills in the Kanpur area of northern India. Column experiments were conducted under water-saturated conditions to simulate Cr release from the wastes caused by tropical heavy-rain events. Leached Cr(VI) decreased from 1,800 to 300 mg L−1 (Rania site) and 1,200 to 163 mg L−1 (Chhiwali site) during exchange of 12 pore volumes, which approximately corresponds to 2 yr of monsoon precipitation. Flow interruptions for 10, 100, and 1,000 h had little effect on Cr(VI) concentrations in the leachate, suggesting that Cr(VI) leaching was not limited by slow release kinetics. Calcium aluminum chromium oxide hydrates (CAC), and highly soluble phases such as Na2CrO4 may play a role in controlling Cr(VI) concentration in the leachates. The amount of Cr(VI) leached from the columns accounted for 16% of the total Cr(VI) present in both COPR samples. A decrease in the solid-phase Cr(VI)/Crtotal ratio along the column was identified by X-ray absorption near edge structure (XANES) spectroscopy. Consistently, the smallest Cr(VI)/Crtotal ratios were found in the lower column section closest to the inflow. Our results suggest that Cr(VI) leaching from the unlined COPR landfills will continue for centuries, highlighting the urgent need to remediate these dumpsites.

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