HR: 11:20h
AN: PP32A-05    [Abstracts]
TI: Freshwater Input to the Gulf of Mexico During the Last Glaciation to Holocene
AU: * Flower, B P
EM: bflower@marine.usf.edu
AF: College of Marine Science University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AU: Hill, H W
EM: hhill@marine.usf.edu
AF: College of Marine Science University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AU: Richey, J N
EM: jrichey@marine.usf.edu
AF: College of Marine Science University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AU: LoDico, J
EM: jlodico@marine.usf.edu
AF: College of Marine Science University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AU: Hastings, D W
EM: hastings@eckerd.edu
AF: Collegium of Natural Sciences Eckerd College, 4200 54th Avenue South, St. Petersburg, FL 33711 United States
AU: Gilbert, M
EM: gilberml@eckerd.edu
AF: Collegium of Natural Sciences Eckerd College, 4200 54th Avenue South, St. Petersburg, FL 33711 United States
AU: Quinn, T M
EM: tquinn@marine.usf.edu
AF: College of Marine Science University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AB: Evidence is emerging that Laurentide Ice Sheet (LIS) melting was decoupled from Greenland air temperature during the last glacial cycle. In particular, ice margin records indicate full retreat of the LIS during Greenland Stadial 2a ca. 16.9-14.7 ka, which spans Heinrich Event 1 in the North Atlantic (Denton et al., 2005). This finding squares with the first evidence from Gulf of Mexico (GOM) sediments for LIS melting beginning ca. 17 ka (Kennett and Shackleton, 1975). Initial melting was clearly before the onset of the Bolling warm interval, and may have been linked to global warming. Thirty years later, development of the Mg/Ca sea-surface temperature (SST) proxy has allowed separation of SST and δ¹⁸Oseawater, which reflects ice volume, meltwater, and regional evaporation-precipitation (E-P) history. Here we summarize paired δ¹⁸O and Mg/Ca data on the planktic foraminifer Globigerinoides ruber from laminated Orca Basin during the last glaciation to Holocene. Isolation of δ¹⁸Oseawater reveals five major episodes of LIS meltwater input from ca. 50-28 ka (Hill et al., 2005) and two episodes from ca. 16.2-13.0 ka (Flower et al., 2004), suggesting that LIS melting did not follow Greenland air temperature throughout the last glacial cycle. LIS melting may instead track global sea level changes. After the demise of the LIS during the early Holocene, δ¹⁸Oseawater data from ca. 10.5-7 ka reveal five excursions of about 0.5‰ indicating substantial E-P changes and Mississippi River input, including a major spike of -0.8‰ ca. 8.4 ka (LoDico et al., submitted). Phasing of SST and δ¹⁸Oseawater indicates substantial influence of GOM SST on hydrology in the Mississippi River drainage basin. Overall, we find significant climatic and hydrologic variability throughout the last glacial cycle with a timing that may reflect low-latitude insolation forcing.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4926 Glacial
DE: 4934 Insolation forcing
DE: 4938 Interhemispheric phasing
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005