HR: 0800h
AN: PP51C-1343    [Abstracts]
TI: Freshwater input into the Gulf of Mexico Prior to the 8.2 cal kyr BP Cool Event in Greenland Ice Core Records
AU: * LoDico, J M
EM: jlodico@marine.usf.edu
AF: Univeristy of South Florida, 140 Seventh Ave South, St. Petersburg, FL 33701 United States
AU: Flower, B P
EM: bflower@mainre.usf.edu
AF: Univeristy of South Florida, 140 Seventh Ave South, St. Petersburg, FL 33701 United States
AU: Quinn, T M
EM: quinn@marine.usf.edu
AF: Univeristy of South Florida, 140 Seventh Ave South, St. Petersburg, FL 33701 United States
AB: The most prominent event recorded in Greenland ice core records over the past 10 calendar kiloyears before present (cal kyr BP) is an abrupt cooling at 8.2 cal kyr BP, which lasted for 300-400 yrs. It has been proposed that this climatic event was caused by a weakening of the thermohaline circulation in the North Atlantic forced by a vast outflow of freshwater through the Hudson Strait from glacial lakes Agassiz and Ojibway. Sediment core MD02-2550 from Orca Basin located in the northern Gulf of Mexico (GOM) provides an early Holocene record (10 to 7 cal kyr BP) of GOM climate changes, input from the Mississippi River system and adjacent continental areas. Paired analysis of Mg/Ca, a proxy of sea surface temperatures (SSTs), and \delta$^{18}$O on the planktonic foraminifera { \it Globigerinoides ruber } (white variety; 250 -350 $\mu$m) sampled at 0.5 cm (providing $\sim$20 year resolution), indicate a large isotopic excursion of $\sim$ -1 $\permil$ \delta$^{18}$O seawater from 8.5 to 8.4 cal kyr BP, coincident with the drainage of glacial lakes Agassiz and Ojibway at 8.47 cal kyr BP. We consider three possible sources for this freshwater pulse: freshwater input from glacial lakes, meltwater input from the drainage of the Laurentide Ice Sheet's final dome, and/or increased precipitation in North American drainage basins. Mg/Ca-SSTs show minimal mean change across the freshwater interval and an average of $\sim$28 $\deg$C from 7 to 10 cal kyr BP, which is within the current mean SSTs for GOM ($\sim$28 $\deg$C). Mg/Ca-SST and \delta$^{18}$O seawater time series contain concentrations of variance near 500, 220, 146, and 60 years, significant at the 90 % confidence level, indicating possible sensitivity to solar variations. Ongoing faunal assemblage work will provide additional assessment for SST, sea surface salinity (SSS) and nutrient changes during the early Holocene in the GOM.
DE: 9350 North America
DE: 3344 Paleoclimatology
DE: 1040 Isotopic composition/chemistry
DE: 1650 Solar variability
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting