HR: 10:35h
AN: PP32A-02    [Abstracts]
TI: Marine Coral and Sediment Records of Intermediate Water History from Decadal to Millennial Timescales on the California Margin
AU: * Hill, T M
EM: tmhill@ucdavis.edu
AF: Department of Geology, University of California, Davis, CA 95616 United States
AU: Kennett, J P
EM: kennett@geol.ucsb.edu
AF: Department of Geological Sciences, University of California, Santa Barbara, CA 93106 United States
AU: Spero, H J
EM: hjspero@ucdavis.edu
AF: Department of Geology, University of California, Davis, CA 95616 United States
AB: Intermediate waters (300-2500m) are critically important to the earth's climate system for the transport of heat and salt around the globe, as well as influencing the carbon cycle via the oxygen minimum zone (OMZ). Results from the California margin indicate that intermediate waters are sensitive to climate change across multiple timescales. Sediment cores in Santa Barbara Basin (MD02-2503 and MD02-2504) provide high-resolution records of surface and intermediate water processes during the most recent deglaciation. Oxygen isotopic values of planktonic and benthic foraminifera indicate that surface and intermediate waters warmed synchronously,~2ka prior to Termination IA. These findings are consistent with previous studies that indicate intermediate waters responded prior to or synchronously with surface waters during major climatic transitions (Kennett et al., 2002; Hendy and Kennett, 2003). Studies from the Santa Barbara Basin also indicate dramatic changes in oxygenation during the Bolling-Allerod, associated with the combined influences of water column methane oxidation, intermediate water ventilation and surface productivity. These studies indicate that intermediate waters are highly sensitive to climate change on millennial timescales. However, it is poorly understood how intermediate waters will respond to climate change on short timescales, such as during ENSO episodes, Pacific Decadal Oscillation mode shifts, or anthropogenic forcing. Investigations of deep-sea bamboo corals collected along the California margin (250-2200m) are utilized to reconstruct the recent environmental history of intermediate waters in this region. Preliminary radiocarbon analyses of four coral specimens from south of Pt. Conception suggest that bamboo corals live for centuries with growth rates of 50-100 microns/year. Radiocarbon content of recently precipitated coral calcite reflects equilibrium with that of ambient seawater (Δ14C_calcite = ¬ 249.7 ‰ Δ14C_DIC = ¬ 242.2 ‰). A preliminary Mg/Ca calibration indicates that this proxy can be used to reconstruct intermediate depth temperatures over time (7% change in Mg/Ca per 1°C). Sr/Ca ratios, interpreted to reflect changes in growth rate, record shifts that correlate to the Pacific Decadal Oscillation. These data provide evidence that short-term changes in the Pacific ocean/atmosphere system are influencing the geochemistry of intermediate water masses.
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4916 Corals (4220)
DE: 4944 Micropaleontology (0459, 3030)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005