HR: 09:45h
AN: PP41A-08    [PDF]
TI: Abrupt Climate Change During the Last Glacial Cycle Based on Gulf of Mexico Sediments
AU: * Flower, B P
EM: bflower@marine.usf.edu
AF: University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AU: Hastings, D W
EM: hastings@eckerd.edu
AF: Eckerd College, 4200 54th Avenue South, St. Petersburg, FL 33711 United States
AU: Hill, H
EM: hhill@marine.usf.edu
AF: University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AU: Quinn, T M
EM: tquinn@marine.usf.edu
AF: University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701 United States
AB: Evidence is emerging that the tropical climate system played a major role in past global climate change during the last glacial cycle. However, existing studies indicate asynchronous temperature variability in the western equatorial Atlantic, complicating the identification of causal mechanisms. Because the Gulf of Mexico (GOM) is linked to the equatorial Atlantic, sea-surface temperature (SST) records from the GOM help assess the phasing between low- and high-latitude Atlantic climate. High sedimentation rates of $>$40 cm/k.y. and laminated sediments in Orca Basin allow sub-centennial-scale resolution. Paired $\delta$$^{18}$O and Mg/Ca data on the planktic foraminifer {\it Globigerinoides ruber} from core EN32-PC6 are used to separate deglacial changes in SST and $\delta$$^{18}$Oseawater due to low-salinity meltwater from the Laurentide Ice Sheet (LIS). Mg-SST increases by $>$3.0$\deg$C between 17.2 and 15.2 ka (calendar years) encompassing Heinrich Event 1 in the North Atlantic. Comparison to polar ice core records indicates GOM SST was not in phase with Greenland air temperature, consistent with thermohaline circulation modulation of Atlantic climate. This warming represents the bulk of the 4.2+/-0.9$\deg$C increase from the last glacial maximum (24.0+/-0.8$\deg$C) to early Holocene (29.0+/-0.4$\deg$C). Subtracting temperature and ice-volume effects from {\it Gs. ruber} $\delta$$^{18}$O reveals two episodes of LIS meltwater input, one of $>$1.5% from ca. 16.2-15.7 ka and a second major spike of $>$2% from ca. 15.2-13.0 ka that encompassed meltwater pulse 1A (mwp-1A) and peaked at ca. 13.4 ka. These results suggest that (1) subtropical Atlantic SST warming preceded peak LIS decay and mwp-1A by $>$2 k.y., (2) thermohaline circulation may have modulated Atlantic climate on the millennial scale during the last deglaciation, and (3) major LIS meltwater input to the GOM ended before North Atlantic Deep Water suppression during the Younger Dryas. A new 31.79 m Calypso piston core collected in July 2002 on the R/V Marion Dufresne (MD02-2551) documents GOM climate variability associated with Dansgaard-Oeschger (D-O) cycles known from Greenland ice records. {\it Gs. ruber} $\delta$$^{18}$O data from the 40-30 ka interval (30 year resolution) reveal cycles of $>$1% amplitude that closely match D-O cycles 8-5, although the relative phasing is complex. Paired $\delta$$^{18}$O and Mg/Ca data indicate that these oscillations reflect significant changes in $\delta$$^{18}$Oseawater that result from changes in evaporation/precipitation balance and LIS meltwater input. Overall, significant sub-centennial- to millennial climate variability persists throughout the last glacial cycle in the GOM.
DE: 1620 Climate dynamics (3309)
DE: 3322 Land/atmosphere interactions
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting