HR: 0800h
AN: PP31D-0649    [Abstracts]
TI: Decadal-scale Climate Variability in the Gulf of Mexico During the Past 3000 Years
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@mail.utexas.edu
AF: Department of Geological Sciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, United States
AB: Understanding 20th century global warming depends in part on documenting natural climate variability beyond the range of instrumental records. However, proxy records of decadal-scale climate variability during the past 3000 years are sparse, especially for low-latitude oceans. Generation of proxy climate records from high accumulation rate sediment cores from the Gulf of Mexico can help evaluate climate variability in the low-latitude North Atlantic region. Here we present paired Mg/Ca and d18O measurements on the planktic foraminifer Globigerinoides ruber (white) from two northern Gulf of Mexico sediment cores that provide decadal-scale records of sea-surface temperature (SST) and d18O of seawater (d18Osw) over the past three thousand years (ka). Mg/Ca SST data exhibit a series of six 0.5 degree C oscillations from ca. 3-1 ka before a 2-3 degree C cooling including the Little Ice Age. These oscillations include warm intervals comparable to mid-20th century levels that may correspond to the Medieval Warm Period ca. 1 ka and the Roman Warm Period ca. 2 ka, but also provide evidence for higher-frequency variability. Time series analysis indicates significant periods in the multi-century band (300-600 years) and the multi-decadal band (60-80 years). Comparison to Sargasso Sea records demonstrates a broadly similar pattern of SST change in the low-latitude North Atlantic Ocean during the past 3 ka. Gulf of Mexico d18Osw, which is at present primarily controlled by Mississippi River input and evaporation- precipitation (E-P), seems to be consistent with some North American continental records. In particular, d18Osw maxima at ca. 2.5, 1.05, and 0.5 ka correlate with previously recognized dry intervals in central North America and the Yucatan peninsula. Gulf of Mexico d18Osw values exhibit significant variability, including strong peaks in the multi-decadal band (60-70 years) that are coherent and in phase with SST, but no change in mean (1.0+/-0.3 per mil) relative to core-top values. Overall, these results support models that suggest the Gulf of Mexico and North America have been strongly influenced by decadal- to century-scale changes in regional atmospheric conditions, including the position and strength of the subtropical high pressure cell.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4936 Interglacial
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting