HR: 0800h
AN: PP21A-1539    [Abstracts]
TI: Elevated Mississippi River discharge during glacial times: A 6,000 year wet period on the North American continent
AU: * Hill, H W
EM: hhill@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701 United States
AU: Hollander, D J
EM: davidh@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701 United States
AU: Flower, B P
EM: bflower@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701 United States
AU: Quinn, T M
EM: tquinn@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701 United States
AB: Sedimentary basins proximal to major rivers can provide a coherent, high-resolution assessment of the oceanic and continental responses to changing hydrologic regimes attributed to abrupt climate variability. Documenting these regime changes under climatic extremes, including glacial time periods that are often considered cold and dry in temperate North America, is important to understand the potential impacts associated with changing hydrologic conditions. The Orca Basin in the northern Gulf of Mexico (GOM) is ideally situated to record inputs from the Mississippi River and to relate these inputs to changing moisture balance over North America. We use organic and inorganic geochemical analyses to document a 6 ka wet period on the North American continent from 32-38 ka, during glacial Marine Isotope Stage 3, that is decoupled from Laurentide Ice Sheet meltwater dynamics over this interval. This wet period is inferred from a 5-fold increase in the input of long-chain n-alkanes derived from terrestrial plants and concurrent increases in the percent coarse fraction and insoluble residue in the bulk sediment. Associated with the wet period, a 5-fold increase in the algal derived n-alkanes implies that continentally sourced nutrients supported marine production. A 0.6 ‰ increase in the inorganic δ¹³C_{G. ruber} and a shift in the δ¹³C of bulk organic matter from -26 to -23 ‰ also points to an increase in marine production. Further, a 1°C cooling in SST, as determined from G.ruber Mg-derived temperatures, is synchronous with the fluvial inputs. Our evidence suggests that the GOM served as an enhanced moisture source to the Mississippi River basin during this interval, perhaps via the southern displacement of frontal weather systems, resulting in oceanic physical and biological changes. Results of this study will be discussed in the context of regionally defined climate patterns, continental paleorecords and global circulation models.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
DE: 4926 Glacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005