HR: 10:50h
AN: PP32B-03    [Abstracts]
TI: Southern Ocean Multi-Decadally Resolved Sea Surface and Intemediate Water Multi Proxy Reconstructions Spanning the A2 Antarctic Warm Event at ODP Site 1233
AU: * Euler, C
EM: christine.euler@bjerknes.uib.no
AF: Dept. of Earth Sciences, University of Bergen, Bergen, 5007, Norway
AU: Marchitto, T M
AF: INSTAAR and Dept. of Geological Sciences, University of Colorado, Boulder, CO 80309, United States
AU: Kleiven, H F
AF: Dept. of Earth Sciences, University of Bergen, Bergen, 5007, Norway
AU: Kleiven, H F
AF: Bjerknes Centre of Climate Research, University of Bergen, Bergen, 5007, Norway
AU: Ninnemann, U S
AF: Dept. of Earth Sciences, University of Bergen, Bergen, 5007, Norway
AU: Ninnemann, U S
AF: Bjerknes Centre of Climate Research, University of Bergen, Bergen, 5007, Norway
AB: Southern Ocean circumpolar dynamics are hypothesized to play an active role in the climate system through their influence on atmospheric carbon dioxide levels, the global thermocline and the ocean overturning circulation. It is increasingly clear that Southern Ocean millennial scale sea surface temperatures show a pattern similar to what is observed in Antarctic ice cores, suggesting southern dynamics play an active part in these events. The full nature and role of these changes cannot be fully understood until higher resolution records are available capturing Southern Westerly Wind (SWW) and Antarctic Intermediate Water signals (AAIW) detailing the timing, rate and amplitude of these events. Here we present a multi-decadal foraminiferal multiproxy reconstruction spanning the A2 Antarctic warm event (here ~44-48 kyr BP, MIS 3) from the region in the southeast Pacific where the SWW and the Antarctic Circumpolar Current (ACC) intersect with the South American continent and freshly formed AAIW is monitored at depth. Ocean Drilling Program (ODP) Site 1233 (41°00'S, 74°27'W, 838m, sedimentation rate ~1.5-2.2 m/kyr) from the Chilean slope monitors simultaneously AAIW and sea surface water properties that are strongly influenced by the climate signals of the large scale atmospheric (SWW) and oceanic systems (ACC). We use a combined foraminiferal approach of planktic, G. bulloides, and benthic, U. peregrina, oxygen isotopes (temperature plus δ¹⁸O_water) and G. bulloides Mg/Ca (temperature). This allows us to 1.) establish a sea surface temperature (SST) signal derived from foraminifera that is easily compared to the benthic record 2.) reconstruct the δ¹⁸O_water using the same foraminiferal species for determining both temperature and δ¹⁸O_foram and 3.) assess the high frequency variability in the sea surface temperature and rate of changes. The Mg/Ca SST reconstruction shows a 2-3°C variability in both high and low frequency. We find that >50% of the amplitude in the planktic δ¹⁸O record is caused by changes in δ¹⁸O_water, much of which is probably related to local fresh water fluxes, due to the fluctuations of the Patagonian ice sheet. The high resolution Mg/Ca SST reconstruction mirrors the lower resolution alkenone-derived SST from site 1233 spanning A2 and is correlated to the changes in benthic foraminiferal δ¹⁸O, approximately with the same magnitude, indicating a broad scale change involving the major circumpolar dynamical systems.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4926 Glacial
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting