Deglacial to Holocene Circumpolar Deep Water influence over the Sabrina Coast continental shelf, East Antarctica
Abstract
Sabrina Coast outlet glaciers drain one eighth ( 3.5 m sea level equivalent ice) of the East Antarctic Ice Sheet and are losing mass. Observations indicate that warm modified Circumpolar Deepwater (mCDW) is accessing regional grounding lines, suggesting susceptibility to ocean thermal forcing. To understand regional ocean-ice interactions from the deglacial ( 18 ka) to the present, we reconstructed oceanographic change in a 13 m diatom mud and ooze sequence collected from the mid-shelf using a suite of sediment coring devices.
We present geochemical and micropaleontological (TEX86, foraminifer stable isotope, Mg/Ca, and diatom assemblages) records, which enable us to assess regional ocean temperatures, meltwater, and sea ice conditions. Upper ocean temperatures reveal deglacial warmth and orbital-scale Holocene cooling. Millennial-scale middle Holocene warmth, associated with increased foraminifer presence and ACC-related diatoms, is temporally coincident with circum-Antarctic warming and ice retreat. The late Holocene is cooler and contains alternating ACC-related and mat-associated diatom laminations, indicative of regional stratification changes. Modern sedimentary records indicate a recent ( 1940's) transition from more stratified to mixed water column conditions and increased mCDW influence. On the Sabrina Coast shelf, mCDW presence is associated with the position/strength of the Antarctic Coastal Current, driven by Southern Hemisphere westerly winds. Our records indicate warm deglacial oceanographic conditions, coincident with other records of atmospheric warming, increasing CO2, and enhanced Southern Ocean upwelling. We hypothesize regional temperature and ice variations are driven by changes in mCDW influence. Support for this hypothesis comes from the similar sedimentary characteristics of the recent and middle Holocene sediments. Thus, Sabrina Coast ice mass loss may continue if the westerlies shift southward, as predicted with continued warming, with implications for ice sheet instability and global sea level rise.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP23E1541V
- Keywords:
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- 3036 Ocean drilling;
- MARINE GEOLOGY AND GEOPHYSICSDE: 4914 Continental climate records;
- PALEOCEANOGRAPHYDE: 4926 Glacial;
- PALEOCEANOGRAPHYDE: 4954 Sea surface temperature;
- PALEOCEANOGRAPHY