Antarctic Holocene Climate Change: Stable Isotopic Record from Palmer Deep

Shevenell, A.E. and Kennett, J.P., Geological Sciences and Marine Science Institute, University of California, Santa Barbara, CA 93106

The first moderate to high-resolution Holocene marine stable isotope record from the near-shore Antarctic continental shelf (ODP Hole 1098B) suggests sensitivity of the western Antarctic Peninsula (western AP) hydrography to westerly wind strength and ENSO-like climate variability. Despite its proximity to corrosive Antarctic water masses, sufficient CaCO₃ exists (especially in the late Holocene) in Palmer Deep (Palmer Deep) sediments to provide a high-quality stable isotopic record. Coherence of benthic foraminifer δ ¹⁸O, δ ¹³ C, sedimentologic, and CaCO₃ fluctuations suggests that rapid (<20 yr) Palmer Deep bottom water temperature fluctuations of 1-1.5°C are associated with competitive interactions between two dominant oceanographic/ climatic states. An abrupt shift from a warm, stable early and middle Holocene (~10 to 3.5ka) Upper Circumpolar Deep Water (UCDW) state to a cool, variable late Holocene (~3.5-0 ka) Shelf Water state occurred at ~3.5 ka. Palmer Deep bottom waters oscillated between UCDW and shelf water-dominated states during the late Holocene. Cool shelf water intervals correlate with Neoglacial events; the most recent and largest being the Little Ice Age (~0.7-0.2 ka). Similarities between Palmer Deep and global Holocene records and the rapidity of inferred bottom water fluctuations suggest that western AP shelf hydrography has not been controlled by abrupt thermohaline reorganizations, but by shifting atmospheric influences that affect the location of the Antarctic Circumpolar Current (ACC). We suggest that these atmospheric perturbations may have originated in the low latitude tropical Pacific.