18 research outputs found
Expedition 382 Preliminary Report: Iceberg Alley and Subantarctic Ice and Ocean Dynamics
This is the final version. Available from International Ocean Discovery Program via the DOI in this record.âŻInternational 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 (U1534âU1538) 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°â59.4°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 U1536âU1538) will be used to study the Neogene flux of icebergs through âIceberg Alley,â 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 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 âwarm interglacialsâ 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 northâsouth variations across the Scotia Sea be- tween 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, oceanâatmosphere 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 recon- struct 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 âcold water route.â The Subantarctic Front contourite drift, deposited between 400 and 2000 m water depth on the northern flank of an eastâwest 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 (~3.1â2.6 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 Sub- antarctic 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.National Science Foundatio
Ice sheetâfree West Antarctica during peak early Oligocene glaciation
One of Earthâs most fundamental climate shifts â the greenhouse-icehouse transition 34 Ma ago â initiated Antarctic ice-sheet build-up, influencing global climate until today. However, the extent of the ice sheet during the Early Oligocene Glacial Maximum (~33.7â33.2 Ma) that immediately followed this transition, a critical knowledge gap for assessing feedbacks between permanently glaciated areas and early Cenozoic global climate reorganization, is uncertain. Here, we present shallow-marine drilling data constraining earliest Oligocene environmental conditions on West Antarcticaâs Pacific margin â a key region for understanding Antarctic ice sheet-evolution. These data indicate a cool-temperate environment, with mild ocean and air temperatures preventing West Antarctic Ice Sheet formation. Climate-ice sheet modeling corroborates a highly asymmetric Antarctic ice sheet, thereby revealing its differential regional response to past and future climatic change
Expedition 382 summary
This is the final version. Available on open access from IODP Publications via the DOI in this recordInternational Ocean Discovery Program 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 (U1534âU1538) 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°â59.4°S in the southern Scotia Sea. We recovered continuously deposited late Neogene sediments 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 U1536âU1538) will be used to study the Neogene flux of icebergs through âIceberg Alley,â 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 âwarm interglacialsâ 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 northâsouth 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, oceanâatmosphere 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 intermediate water formation in the southwest Atlantic responds to changes in connectivity between the Atlantic and Pacific basins, the âcold water route.â The Subantarctic Front contourite drift, deposited between 400 and 2000 m water depth on the northern flank of an eastâwest 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 (~3.1â2.6 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.Natural Environment Research Council (NERC
Ancient marine sediment DNA reveals diatom transition in Antarctica
This is the final version. Available on open access from Nature Research via the DOI in this recordData availability:
The following databases were used in this study: SILVA small (version 132Ref-nr) and large (version 132Ref) subunit ribosomal RNA database (https://www.arb-silva.de/), and psbO55 (https://www.ebi.ac.uk/biostudies/studies/S-BSST659?query=S-BSST659). Detailed Supplementary Information on methods and analysis is provided with this submission. The demultiplexed raw sequencing data generated and analysed during this study have been deposited in the NCBI Sequence Read Archive database (https://www.ncbi.nlm.nih.gov/sra) under Accession code/BioProject PRJNA861836 (BioSamples SAMN29928044 - SAMN29928123)59, and includes metadata for each sediment and control sample. For further requests please contact the corresponding author. Source data are provided with this paper.Code availability:
The bioinformatic pipeline used in this study was previously published in ref. 8 and additional information is provided with the Supplementary Information Notes 1â3.Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, psbO). We find evidence of warm phases being associated with high relative diatom abundance, and a marked transition from diatoms comprising <10% of all eukaryotes prior to ~14.5 ka, to ~50% after this time, i.e., following Meltwater Pulse 1A, alongside a composition change from sea-ice to open-ocean species. Our study demonstrates that sedaDNA tools can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and paleo-productivity phases throughout multiple glacial-interglacial cycles.Australian and New Zealand International Ocean Discovery Program Consortium (ANZIC)University of AdelaideAustralian Research Council (ARC)Deutsche Forschungsgemeinschaft (DFG)NASANational Science Foundation (NSF)Dutch Research Council (NWO)European Union Horizon 202
Episodes of early Pleistocene West Antarctic Ice Sheet retreat recorded by Iceberg Alley sediments
Open Research:
All 40Ar/39Ar ages, QEMSCAN SEM data, and depth-age ties between NGR data from Hole
U1538A (Bailey et al., 2022), the Dove Basin stack (Reilly et al., 2020) and all other shipboard expedition data presented here (Reilly et al., 2021) are archived in the IODP community at zenodo.org.This is the final version. Available from Wiley via the DOI in this record.âŻIce loss in the Southern Hemisphere has been greatest over the past 30 years in West Antarctica. The high sensitivity of this region to climate change has motivated geologists to examine marine sedimentary records for evidence of past episodes of West Antarctic Ice Sheet (WAIS) instability. Sediments accumulating in the Scotia Sea are useful to examine for this purpose because they receive iceberg-rafted debris (IBRD) sourced from the Pacific- and Atlantic-facing sectors of West Antarctica. Here we report on the sedimentology and provenance of the oldest of three cm-scale coarse-grained layers recovered from this sea at International Ocean Discovery Program Site U1538. These layers are preserved in opal-rich sediments deposited âź1.2 Ma during a relatively warm regional climate. Our microCT-based analysis of the layer's in-situ fabric confirms its ice-rafted origin. We further infer that it is the product of an intense but short-lived episode of IBRD deposition. Based on the petrography of its sand fraction and the Phanerozoic 40Ar/39Ar ages of hornblende and mica it contains, we conclude that the IBRD it contains was likely sourced from the Weddell Sea and/or Amundsen Sea embayment(s) of West Antarctica. We attribute the high concentrations of IBRD in these layers to âdirtyâ icebergs calved from the WAIS following its retreat inland from its modern grounding line. These layers also sit at the top of a âź366-m thick Pliocene and early Pleistocene sequence that is much more dropstone-rich than its overlying sediments. We speculate this fact may reflect that WAIS mass-balance was highly dynamic during the âź41-kyr (inter)glacial world.National Science FoundationNational Science FoundationNational Science FoundationNational Science FoundationNatural Environment Research CouncilNatural Environment Research CouncilHorizon 2020 research and innovation programme - Marie Sklodowska-CurieDFG-Priority Programme 527NASAARC DECRA FellowshipSpanish MINECOSpanish MINECOOregon State UniversityDivision of Earth SciencesOffice of Polar ProgramsColumbia UniversityOffice of Nuclear EnergyDeutsche ForschungsgemeinschaftNational Aeronautics and Space AdministrationAustralian Research CouncilScientific Committee on Antarctic Researc
New magnetostratigraphic insights from Iceberg Alley on the rhythms of Antarctic climate during the PlioâPleistocene
International Ocean Discovery Program (IODP) Expedition 382 in the Scotia Seaâs Iceberg
Alley recovered among the most continuous and highest resolution stratigraphic records in the Southern
Ocean near Antarctica spanning the last 3.3 Myr. Sites drilled in Dove Basin (U1536/U1537) have
well-resolved magnetostratigraphy and a strong imprint of orbital forcing in their lithostratigraphy. All
magnetic reversals of the last 3.3 Myr are identified, providing a robust age model independent of orbital
tuning. During the Pleistocene, alternation of terrigenous versus diatomaceous facies shows power in
the eccentricity and obliquity frequencies comparable to the amplitude modulation of benthic δ18O
records. This suggests that variations in Dove Basin lithostratigraphy during the Pleistocene reflect a
similar history as globally integrated ice volume at these frequencies. However, power in the precession
frequencies over the entire âź3.3 Myr record does not match the amplitude modulation of benthic δ18O
records, suggesting Dove Basin contains a unique record at these frequencies. Comparing the position of
magnetic reversals relative to local facies changes in Dove Basin and the same magnetic reversals relative
to benthic δ18O at North Atlantic IODP Site U1308, we demonstrate Dove Basin facies change at different
times than benthic δ18O during intervals between âź3 and 1 Ma. These differences are consistent with
precession phase shifts and suggest climate signals with a Southern Hemisphere summer insolation phase were recorded around Antarctica. If Dove Basin lithology reflects local Antarctic ice volume changes, these signals could represent ice sheet precession-paced variations not captured in benthic δ18O during the 41-kyr world.Postprin
Latitudinal variance in the drivers and pacing of warmth during mid-Pleistocene MIS 31 in the Antarctic Zone of the Southern Ocean
This is the author accepted manuscriptOpen Research: Data generated for this work, diatom relative and absolute abundance data, are available in the supplemental materials.Early Pleistocene Marine Isotope Stage (MIS)-31 (1.081 to 1.062 Ma) is a unique interval of extreme global warming, including evidence of a West Antarctic Ice Sheet (WAIS) collapse. Here we present a new 1000-year resolution, spanning 1.110-1.030 Ma, diatom-based reconstruction of primary productivity, relative sea surface temperature changes, sea-ice proximity/open ocean conditions and diatom species absolute abundances during MIS-31, from the Scotia Sea (59° S) using deep-sea sediments collected during International Ocean Discovery Program (IODP) Expedition 382. The lower Jaramillo magnetic reversal (base of C1r.1n, 1.071 Ma) provides a robust and independent time-stratigraphic marker to correlate records from other drill cores in the Antarctic Zone of the Southern Ocean (AZSO). An increase in open ocean species Fragilariopsis kerguelensis in early MIS-31 at 53° S (Ocean Drilling Program Site 1094) correlates with increased obliquity forcing, whereas at 59° S (IODP Site U1537; this study) three progressively increasing, successive peaks in the relative abundance of F. kerguelensis correlate with Southern Hemisphere-phased precession pacing. These observations reveal a complex pattern of ocean temperature change and sustained sea surface temperature increase lasting longer than a precession cycle within the Atlantic sector of the AZSO. Timing of an inferred WAIS collapse is consistent with delayed warmth (possibly driven by sea-ice dynamics) in the southern AZSO, supporting models that indicate WAIS sensitivity to local sub-ice shelf melting. Anthropogenically enhanced impingement of relatively warm water beneath the ice shelves today highlights the importance of understanding dynamic responses of the WAIS during MIS-31, a warmer than Holocene interglacial.National Science Foundation (NSF)Deutsche ForschungsgemeinschaftEuropean Union Horizon 2020Natural Environment Research Council (NERC)Australian Research Council (ARC)Australian and New Zealand International Ocean Discovery Program Consortiu
Enhanced North Pacific deep-ocean stratification by stronger intermediate water formation during Heinrich Stadial 1
Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years.
The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5âMa, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9âMa. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4âMa. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels