Gulf of Mexico Sea-Surface Temperatures and Laurentide Meltwater Input During MIS 3: Implications for High/Low Latitude Linkages

A new sediment core from the Orca Basin, Gulf of Mexico, will be helpful in determining the role of low latitude ocean dynamics in rapid climate change. The 31.79-m core (MD02-2551; 26^o56.78'N, 91^o21.75'W), obtained in July 2002 aboard the R/V Marion Dufrense will provide, for the first time, an opportunity to study Gulf of Mexico sea-surface temperature (SST) and sea-surface salinity (SSS), as well as meltwater input from the Laurentide Ice Sheet (LIS) during the Dansgaard-Oeschger (D-O) cycles found in Marine Isotope Stage (MIS) 3, 24-57 ka. The anoxic Orca Basin, which sits 290 km south of the Mississippi Delta, is filled with a hypersaline brine resulting in undisturbed laminations and excellent preservation of planktonic foraminifera. A coarse resolution isotope stratigraphy of the core using Globigerinoides ruber (pink and white variety) with a size fraction from 250-355 microns and faunal abundances suggests the oldest sediments are from MIS 3, resulting in an average sedimentation rate of >50 cm/1000 years. A distinct negative isotope anomaly, reaching δ¹⁸O -4 ‰ based on pink G. ruber, occurs at 2625 cm, which is best explained by increased meltwater input from the LIS. More detailed work on the core, including AMS ¹⁴C age control, will demonstrate how SST and meltwater input relate to D-O events. Multi-proxy data, including δ¹⁸O, Mg/Ca and Uk'37, make it possible to deconvolve SST and SSS. Understanding the relationship between subtropical SST, Greenland air temperatures and high latitude SST, in addition to LIS meltwater input, will test the hypothesis that subtropical SST changes lead high-latitude climate change.