ALBERT

Description: International Ocean Discovery Program (IODP) Expedition 382, Iceberg Alley and Subantarctic Ice and Ocean Dynamics, investigated the long-term climate history of Antarctica, seeking to understand how polar ice sheets responded to changes in insolation and atmospheric CO2 in the past and how ice sheet evolution influenced global sea level and vice versa. Five sites (U1534–U1538) were drilled east of the Drake Passage: two sites at 53.2°S at the northern edge of the Scotia Sea and three sites at 57.4°–59.4°S in the southern Scotia Sea. We recovered continuously deposited late Neogene sediment to reconstruct the past history and variability in Antarctic Ice Sheet (AIS) mass loss and associated changes in oceanic and atmospheric circulation. The sites from the southern Scotia Sea (Sites U1536–U1538) will be used to study the Neogene flux of icebergs through “Iceberg Alley,” the main pathway along which icebergs calved from the margin of the AIS travel as they move equatorward into the warmer waters of the Antarctic Circumpolar Current (ACC). In particular, sediments from this area will allow us to assess the magnitude of iceberg flux during key times of AIS evolution, including the following: The middle Miocene glacial intensification of the East Antarctic Ice Sheet, The mid-Pliocene warm period, The late Pliocene glacial expansion of the West Antarctic Ice Sheet, The mid-Pleistocene transition (MPT), and The “warm interglacials” and glacial terminations of the last 800 ky. We will use the geochemical provenance of iceberg-rafted detritus and other glacially eroded material to determine regional sources of AIS mass loss. We will also address interhemispheric phasing of ice sheet growth and decay, study the distribution and history of land-based versus marine-based ice sheets around the continent over time, and explore the links between AIS variability and global sea level. By comparing north–south variations across the Scotia Sea between the Pirie Basin (Site U1538) and the Dove Basin (Sites U1536 and U1537), Expedition 382 will also deliver critical information on how climate changes in the Southern Ocean affect ocean circulation through the Drake Passage, meridional overturning in the region, water mass production, ocean–atmosphere CO2 transfer by wind-induced upwelling, sea ice variability, bottom water outflow from the Weddell Sea, Antarctic weathering inputs, and changes in oceanic and atmospheric fronts in the vicinity of the ACC. Comparing changes in dust proxy records between the Scotia Sea and Antarctic ice cores will also provide a detailed reconstruction of changes in the Southern Hemisphere westerlies on millennial and orbital timescales for the last 800 ky. Extending the ocean dust record beyond the last 800 ky will help to evaluate dust-climate couplings since the Pliocene, the potential role of dust in iron fertilization and atmospheric CO2 drawdown during glacials, and whether dust input to Antarctica played a role in the MPT. The principal scientific objective of Subantarctic Front Sites U1534 and U1535 at the northern limit of the Scotia Sea is to reconstruct and understand how ocean circulation and intermediate water formation responds to changes in climate with a special focus on the connectivity between the Atlantic and Pacific basins, the “cold water route.” The Subantarctic Front contourite drift, deposited between 400 and 2000 m water depth on the northern flank of an east–west trending trough off the Chilean continental shelf, is ideally situated to monitor millennial- to orbital-scale variability in the export of Antarctic Intermediate Water beneath the Subantarctic Front. During Expedition 382, we recovered continuously deposited sediments from this drift spanning the late Pleistocene (from ~0.78 Ma to recent) and from the late Pliocene (~3.1–2.6 Ma). These sites are expected to yield a wide array of paleoceanographic records that can be used to interpret past changes in the density structure of the Atlantic sector of the Southern Ocean, track migrations of the Subantarctic Front, and give insights into the role and evolution of the cold water route over significant climate episodes, including the following: The most recent warm interglacials of the late Pleistocene and The intensification of Northern Hemisphere glaciation.

Description: International Ocean Discovery Program Expedition 382, Ice-berg Alley and Subantarctic Ice and Ocean Dynamics, investigatedthe long-term climate history of Antarctica, seeking to understandhow polar ice sheets responded to changes in insolation and atmo-spheric CO2 in the past and how ice sheet evolution influencedglobal sea level and vice versa. Five sites (U1534–U1538) weredrilled east of the Drake Passage: two sites at 53.2°S at the northernedge of the Scotia Sea and three sites at 57.4°–59.4°S in the southernScotia Sea. We recovered continuously deposited late Neogene sed-iments to reconstruct the past history and variability in AntarcticIce Sheet (AIS) mass loss and associated changes in oceanic and at-mospheric circulation.The sites from the southern Scotia Sea (Sites U1536–U1538)will be used to study the Neogene flux of icebergs through “IcebergAlley,” the main pathway along which icebergs calved from the mar-gin of the AIS travel as they move equatorward into the warmer wa-ters of the Antarctic Circumpolar Current (ACC). In particular,sediments from this area will allow us to assess the magnitude oficeberg flux during key times of AIS evolution, including the follow-ing: •The middle Miocene glacial intensification of the East Antarctic Ice Sheet, •The mid-Pliocene warm period, •The late Pliocene glacial expansion of the West Antarctic Ice Sheet, •The mid-Pleistocene transition (MPT), and •The “warm interglacials” and glacial terminations of the last 800 ky. We will use the geochemical provenance of iceberg-rafted detri-tus and other glacially eroded material to determine regionalsources of AIS mass loss. We will also address interhemisphericphasing of ice sheet growth and decay, study the distribution andhistory of land-based versus marine-based ice sheets around thecontinent over time, and explore the links between AIS variabilityand global sea level.By comparing north–south variations across the Scotia Sea be-tween the Pirie Basin (Site U1538) and the Dove Basin (Sites U1536and U1537), Expedition 382 will also deliver critical information onhow climate changes in the Southern Ocean affect ocean circulationthrough the Drake Passage, meridional overturning in the region,water mass production, ocean–atmosphere CO2 transfer by wind-induced upwelling, sea ice variability, bottom water outflow fromthe Weddell Sea, Antarctic weathering inputs, and changes in oce-anic and atmospheric fronts in the vicinity of the ACC.Comparing changes in dust proxy records between the ScotiaSea and Antarctic ice cores will also provide a detailed reconstruc-tion of changes in the Southern Hemisphere westerlies on millen-nial and orbital timescales for the last 800 ky. Extending the oceandust record beyond the last 800 ky will help to evaluate dust-climatecouplings since the Pliocene, the potential role of dust in iron fertil-ization and atmospheric CO2 drawdown during glacials, andwhether dust input to Antarctica played a role in the MPT. The principal scientific objective of Subantarctic Front SitesU1534 and U1535 at the northern limit of the Scotia Sea is to recon-struct and understand how intermediate water formation in thesouthwest Atlantic responds to changes in connectivity between theAtlantic and Pacific basins, the “cold water route.” The SubantarcticFront contourite drift, deposited between 400 and 2000 m waterdepth on the northern flank of an east–west trending trough off theChilean continental shelf, is ideally situated to monitor millennial-to orbital-scale variability in the export of Antarctic IntermediateWater beneath the Subantarctic Front. During Expedition 382, werecovered continuously deposited sediments from this drift span-ning the late Pleistocene (from ~0.78 Ma to recent) and from thelate Pliocene (~3.1–2.6 Ma). These sites are expected to yield a widearray of paleoceanographic records that can be used to interpretpast changes in the density structure of the Atlantic sector of theSouthern Ocean, track migrations of the Subantarctic Front, andgive insights into the role and evolution of the cold water route oversignificant climate episodes, including the following: •The most recent warm interglacials of the late Pleistocene and •The intensification of Northern Hemisphere glaciation.

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Waelbroeck, C., Lougheed, B. C., Riveiros, N. V., Missiaen, L., Pedro, J., Dokken, T., Hajdas, I., Wacker, L., Abbott, P., Dumoulin, J., Thil, F., Eynaud, F., Rossignol, L., Fersi, W., Albuquerque, A. L., Arz, H., Austin, W. E. N., Came, R., Carlson, A. E., Collins, J. A., Dennielou, B., Desprat, S., Dickson, A., Elliot, M., Farmer, C., Giraudeau, J., Gottschalk, J., Henderiks, J., Hughen, K., Jung, S., Knutz, P., Lebreiro, S., Lund, D. C., Lynch-Stieglitz, J., Malaize, B., Marchitto, T., Martinez-Mendez, G., Mollenhauer, G., Naughton, F., Nave, S., Nuernberg, D., Oppo, D., Peck, V., Peeters, F. J. C., Penaud, A., Portilho-Ramos, R. d. C., Repschlaeger, J., Roberts, J., Ruehlemann, C., Salgueiro, E., Goni, M. F. S., Schonfeld, J., Scussolini, P., Skinner, L. C., Skonieczny, C., Thornalley, D., Toucanne, S., Van Rooij, D., Vidal, L., Voelker, A. H. L., Wary, M., Weldeab, S., & Ziegler, M. Consistently dated Atlantic sediment cores over the last 40 thousand years. Scientific Data, 6, (2019): 165, doi:10.1038/s41597-019-0173-8.

Description: Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.

Description: The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013 Grant agreement n° 339108). New 14C dates for cores EW9209-1JPC and V29-202 were funded by NSF OCE grants to DWO. FN, ES and AV acknowledge FCT funding support through project UID/Multi/04326/2019. We thank T. Garlan and P. Guyomard for having given us access to cores from the Service Hydrographique et Océanographique de la Marine. We acknowledge N. Smialkowski for help with formatting the data into text files, and L. Mauclair, L. Leroy and G. Isguder for the picking of numerous foraminifer samples for radiocarbon dating. We are grateful to S. Obrochta, E. Cortijo, E. Michel, F. Bassinot, J.C. Duplessy, and L. Labeyrie for advice and fruitful discussions. This paper is LSCE contribution 6572.

Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth-Science Reviews 169 (2017): 132–145, doi:10.1016/j.earscirev.2017.04.005.

Description: The impact of anthropogenic ocean acidification (OA) on marine ecosystems is a vital concern facing marine scientists and managers of ocean resources. Euthecosomatous pteropods (holoplanktonic gastropods) represent an excellent sentinel for indicating exposure to anthropogenic OA because of the sensitivity of their aragonite shells to the OA conditions less favorable for calcification. However, an integration of observations, experiments and modelling efforts is needed to make accurate predictions of how these organisms will respond to future changes to their environment. Our understanding of the underlying organismal biology and life history is far from complete and must be improved if we are to comprehend fully the responses of these organisms to the multitude of stressors in their environment beyond OA. This review considers the present state of research and understanding of euthecosomatous pteropod biology and ecology of these organisms and considers promising new laboratory methods, advances in instrumentation (such as molecular, trace elements, stable isotopes, palaeobiology alongside autonomous sampling platforms, CT scanning and high-quality video recording) and novel field-based approaches (i.e. studies of upwelling and CO2 vent regions) that may allow us to improve our predictive capacity of their vulnerability and/or resilience. In addition to playing a critical ecological and biogeochemical role, pteropods can offer a significant value as an early-indicator of anthropogenic OA. This role as a sentinel species should be developed further to consolidate their potential use within marine environmental management policy making.

Description: M.I. Berning is financed by the German Research Foundation Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas (Project DFG-1158 SCHR 667/15-1).

Description: The East Antarctic Ice Sheet discharges into the Weddell Sea via the Coats Land ice margin. We have used geophysical data to determine the changing ice sheet configuration in this region through its last advance and retreat, and identify constraints on its future stability. Methods included high-resolution multibeam-bathymetry, sub-bottom profiles, seismic-reflection profiles, sediment core analysis and satellite altimetry. These provide evidence that Coats Land glaciers and ice streams merged with the palaeo-Filchner Ice Stream during the last ice advance. Retreat of this ice stream from 12.8 to 8.4 cal kyr BP resulted in its progressive southwards decoupling from Coats Land glaciers. Moraines and grounding-zone wedges document the subsequent retreat and thinning of these glaciers, loss of contact with the bed, and the formation of ice shelves, which re-advanced to pinning points on topographic highs at the distal end of their troughs. Once detached from the bed, the ice shelves were predisposed to rapid retreat back to coastal grounding lines due to reverse-bed slopes, the absence of further pinning points, and potentially to the loss of structural integrity propagating from the grounding line. These processes explain why there are no large ice shelves from 75.5-77° S.

Description: The East Antarctic Ice Sheet discharges into the Weddell Sea via the Coats Land ice margin. We have used geophysical data to determine the changing ice-sheet configuration in this region through its last glacial advance and Holocene retreat and to identify constraints on its future stability. Methods included high-resolution multibeam bathymetry, sub-bottom profiles, seismic-reflection profiles, sediment core analysis and satellite altimetry. These provide evidence that Coats Land glaciers and ice streams merged with the palaeo-Filchner Ice Stream during the last glacial advance. Retreat of this ice stream from 12 848 to 8351 cal. yr BP resulted in its progressive southwards decoupling from Coats Land outlet glaciers. Moraines and grounding-zone wedges document the subsequent retreat and thinning of these glaciers, their loss of contact with the bed and the formation of ice shelves, which re-advanced to pinning points on topographic highs at the distal end of the troughs. Once fully detached from the bed, these ice shelves were predisposed to rapid retreat back to coastal grounding lines. This was due to reverse-bed slopes, the consequent absence of further pinning points in the troughs and potentially to the loss of structural integrity resulting from weaknesses inherited at the grounding line. These processes explain why there are no large ice shelves in the eastern Weddell Sea between 75.5 and 77∘ S.