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SUMMARY:Orbital forcing of western Antarctic Peninsula Holocene climate - 
 Amelia Shevenell
DTSTART:20090512T153000Z
DTEND:20090512T163000Z
UID:TALK17188@talks.cam.ac.uk
CONTACT:Alex Piotrowski
DESCRIPTION:The disintegration of ice shelves\, reduced sea ice extent\, a
 nd\nshifting ecologic zones observed around West Antarctica\, especially\n
 the Antarctic Peninsula\, highlight the impact of recent atmospheric\nand 
 oceanic warming in a climatically sensitive region. To place these\nenviro
 nmental changes in the context of long-term variability\,\nreconstructions
  of the regional Holocene (13\,000-0 years before\npresent) climate state 
 are required. As ocean temperatures likely\ninfluence Antarctic ice shelf/
 ice sheet stability and sea ice extent\,\nrobust geochemical records of pa
 st Southern Ocean sea surface\ntemperatures (SSTs) are essential for under
 standing the mechanisms\nforcing Antarctic climate and cryosphere variabil
 ity. While ice cores\nprovide detailed records of past near-surface temper
 ature\, obtaining\nhigh-resolution SST records from Antarctic continental 
 margin marine\nsediments has proven difficult due to a dearth of calcium c
 arbonate\nneeded for traditional paleotemperature studies. Here we report\
 nmeasurements of TEX86\, an organic paleothermometer based on the\nsedimen
 tary distribution of membrane lipids of pelagic marine Archaea\,\nin a sui
 te of core-top and Holocene (0-12 ka) marine sediments from\nthe western A
 ntarctic Peninsula continental margin. We use regional\nsurface sediments 
 paired with measured temperature data to demonstrate\nthe utility of TEX86
  in Antarctic margin sediments and enhance\nexisting calibrations from 0 t
 o 5°C. Down-core TEX86 measurements\nindicate a long-term Holocene coolin
 g of ~3°C with millennial-scale\nvariability superimposed. Similarities b
 etween our SST record and\nAntarctic ice core records suggest strong ocean
 -atmosphere coupling\nthroughout the Holocene. The long-term SST trend is 
 likely driven by\nlocal insolation forcing\, while millennial-scale change
  may relate to\nvariations in deep-ocean convection influenced by changes 
 in the rate\nof meridional overturning circulation and/or the location and
  strength\nof the westerly wind field.
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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