Orbital forcing of western Antarctic Peninsula Holocene climate

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• Amelia Shevenell
• Tuesday 12 May 2009, 16:30-17:30
• Harker 1 seminar room, Department of Earth Sciences.

If you have a question about this talk, please contact Alex Piotrowski.

The disintegration of ice shelves, reduced sea ice extent, and shifting ecologic zones observed around West Antarctica, especially the Antarctic Peninsula, highlight the impact of recent atmospheric and oceanic warming in a climatically sensitive region. To place these environmental changes in the context of long-term variability, reconstructions of the regional Holocene (13,000-0 years before present) climate state are required. As ocean temperatures likely influence Antarctic ice shelf/ice sheet stability and sea ice extent, robust geochemical records of past Southern Ocean sea surface temperatures (SSTs) are essential for understanding the mechanisms forcing Antarctic climate and cryosphere variability. While ice cores provide detailed records of past near-surface temperature, obtaining high-resolution SST records from Antarctic continental margin marine sediments has proven difficult due to a dearth of calcium carbonate needed for traditional paleotemperature studies. Here we report measurements of TEX86 , an organic paleothermometer based on the sedimentary distribution of membrane lipids of pelagic marine Archaea, in a suite of core-top and Holocene (0-12 ka) marine sediments from the western Antarctic Peninsula continental margin. We use regional surface sediments paired with measured temperature data to demonstrate the utility of TEX86 in Antarctic margin sediments and enhance existing calibrations from 0 to 5°C. Down-core TEX86 measurements indicate a long-term Holocene cooling of ~3°C with millennial-scale variability superimposed. Similarities between our SST record and Antarctic ice core records suggest strong ocean-atmosphere coupling throughout the Holocene. The long-term SST trend is likely driven by local insolation forcing, while millennial-scale change may relate to variations in deep-ocean convection influenced by changes in the rate of meridional overturning circulation and/or the location and strength of the westerly wind field.

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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