HR: 0800h
AN: PP41C-0676    [Abstracts]
TI: Coupling Between Southern Hemisphere Climate and AAIW Revealed by Decadally Sampled Records of sub Antarctic Surface and Intermediate Water Property Changes from 20-75 ka
AU: * Kleiven, H F
EM: kikki@uib.no
AF: Bjerknes Centre of Climate Research, University of Bergen, Allegaten 55, Bergen, N-5007, Norway
AU: * Kleiven, H F
EM: kikki@uib.no
AF: Department of Earth Science, University of Bergen, Allegaten 41, Bergen, N-5007, Norway
AU: Ninnemann, U S
EM: ulysses@uib.no
AF: Bjerknes Centre of Climate Research, University of Bergen, Allegaten 55, Bergen, N-5007, Norway
AU: Ninnemann, U S
EM: ulysses@uib.no
AF: Department of Earth Science, University of Bergen, Allegaten 41, Bergen, N-5007, Norway
AU: Foerde, A
EM: anneelin@gmail.com
AF: Department of Earth Science, University of Bergen, Allegaten 41, Bergen, N-5007, Norway
AB: Ocean Drilling Program (ODP) Site 1233 (41°00'S, 74°27'W, 838m) provides an essential marine counterpart to the recent high resolution EPICA ice core from Dronning Maud Land: monitoring changes in circumpolar ocean circulation and water masses. ODP Site 1233 is situated beneath the northernmost reaches of the Southern Westerlies at a water depth intersecting Antarctic Intermediate Water (AAIW) and is thus perfectly located to fill crucial gaps in our knowledge of key Southern Hemisphere processes. Here we report decadally resolved planktonic and benthic foraminiferal isotopic records spanning MIS 3 (20-75 ka) from this exceptionally high sedimentation rate core (2.2m/kyr) retrieved from the Chilean slope. The benthic foraminiferal carbon and oxygen isotopic records monitor the physical and chemical properties of AAIW close to its source in the SE Pacific, while the planktonic isotopic records monitor the near surface water properties and the large scale atmospheric (Westerlies) and oceanic (ACC) systems influencing them. Our planktonic records suggest that surface water properties varied on multi-centennial to millennial timescales throughout MIS 3, while our bottom water proxy suggests that these surface water warmings were accompanied by concomitant changes in AAIW properties. As in the records of air temperature from Antarctica, warm events appear relatively symmetric; there is no systematic difference in the rate of warming versus cooling, and the bulk of both warming and cooling is often accomplished in as little as a few decades. The extremely rapid rate at which these surface and intermediate ocean changes are accomplished is indicative of their origin. Such abrupt and concurrent shifts in extratropical surface and intermediate ocean properties are most likely driven by changes in the major dynamical systems of Southern Hemisphere ocean and atmospheric circulation which govern their properties today (the Westerlies and the ACC). The similarity in timing and rate of these changes on the fringes of the Southern Ocean relative to those recorded closer to the pole in the new ice core records suggests that such changes are broadly felt and the involve the major circumpolar dynamical systems: resulting in their propagation into the ocean interior. We discuss what implications such abrupt, synoptic scale changes in Antarctic climate and dynamics have on the origin and propagation of abrupt climate change.
DE: 3036 Ocean drilling
DE: 4870 Stable isotopes (0454, 1041)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting