HR: 09:45h
AN: PP11C-08    [Abstracts]
TI: An 800-Year Record of Sediment-Derived, Instrumentally-Calibrated Foraminiferal Mg/Ca SST Estimates From the Tropical North Atlantic
AU: * Black, D E
EM: dblack1@uakron.edu
AF: Dept. of Geology, Univ. of Akron, 252 Buchtel Common, Akron, OH 44325-4101 United States
AU: Abahazi, M A
PP11C-08 AF: Dept. of Geology, Univ. of Akron, 252 Buchtel Common, Akron, OH 44325-4101 United States
AU: Thunell, R C
EM: thunell@geol.sc.edu
AF: Dept. of Geological Sciences, Univ. of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AU: Tappa, E J
EM: ejt@geol.sc.edu
AF: Dept. of Geological Sciences, Univ. of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AB: Most geochemical paleoclimate proxies are calibrated to different climate variables using laboratory culture, surface sediment, or sediment trap experiments. The varved, high-deposition rate sediments of the Cariaco Basin (Venezuela) provide the nearly unique opportunity to compare and calibrate paleoceanographic proxy data directly against true oceanic historical instrumental climate records. Here we present one of the first sediment-derived foraminiferal-Mg/Ca to SST calibrations spanning A. D. 1870-1990. The record of Mg/Ca-estimated tropical North Atlantic SSTs is then extended back to approximately A. D. 1200. Box core PL07-73 BC, recovered from the northeastern slope of Cariaco Basin, was sampled at consecutive 1 mm increments and processed for foraminiferal population, stable isotope, and Mg/Ca (by ICP-AES) analyses. The age model for this core was established by correlating faunal population records from PL07-73 to a nearby very well-dated Cariaco Basin box core, PL07-71 BC. The resulting age model yields consecutive sample intervals of one to two years. Mg/Ca ratios measured on Globigerina bulloides in samples deposited between A. D. 1870 and 1990 were calibrated to monthly SSTs from the Met Office Hadley Centre's SST data set for the Cariaco Basin grid square. Annual correlations between G. bulloides Mg/Ca and instrumental SST were highest (r=0.6, p<.0001, n=120) for the months of March, April, and May, the time when sediment trap studies indicate G. bulloides is most abundant in the basin. The full-length Mg/Ca-estimated SST record is characterized by decadal- and centennial-scale variability. The tropical western North Atlantic does not appear to have experienced a pronounced Medieval Warm Period relative to the complete record. However, strong Little Ice Age cooling of as much as 3 ° C occurred between A. D. 1525 and 1625. Spring SSTs gradually rose between A. D. 1650 and 1900 followed by a 2.5 ° C warming over the 20th century.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4924 Geochemical tracers
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005