HR: 15:10h
AN: PP33C-07    [Abstracts]
TI: Multiproxy Deglacial Record of Climate Change in Central Florida
AU: * Hastings, D W
EM: hastindw@eckerd.edu
AF: Eckerd College, Marine Science, 4200 54 th Ave S, St. Petersburg, FL 33711, United States
AU: Hollweg, T
EM: terill.hollweg@uconn.edu
AF: University of Connecticut, Dept of Marine Sciences?1080 Shennecossett Road, Groton, CT 06340, United States
AU: Flower, B P
EM: bflower@marine.usf.edu
AF: College of Marine Science, Univ of S. Florida 140 7th Avenue South, St. Petersburg, FL 33701, United States
AU: Cronin, T M
AF: US Geological Survey, 926A National Center, Reston, VA 20192, United States
AU: Willard, D A
AF: US Geological Survey, 926A National Center, Reston, VA 20192, United States
AU: Quinn, T M
AF: University of Texas at Austin, Geol Science Dept 1 University Station, Austin, TX 78712, United States
AB: An 11.28 m core from Tampa Bay, Fl (MD02 2579) reveals lacustrine sediments during the deglacial warming. Nineteen AMS radiocarbon dates were used to establish the chronology. Mg/Ca, Sr/Ca and ¹⁸O were measured on two species of brackish water ostracodes, Candona annae and Limnocythere floridensis. Variations in Mg/Ca and Sr/Ca reflect changes in water chemistry, which is related to evaporation/precipitation (E/P) or net moisture. Higher Me/Ca values imply increased evaporation and/or reduced precipitation during drier climates and vice-versa. Downcore trends for both elemental ratios and for both species are remarkably similar. Minor element ratios decrease by 20-30% from 20 to 17 ka, reflecting drier conditions during the LGM. High values at 14.3 ka decrease dramatically to minimum values at 14.1 ka suggesting moist conditions at 14.1 ka. These ratios increase by a factor of two from 14.1 to 12.9 ka with the driest conditions at the onset of the Younger Dryas (YD). Me/Ca ratios decrease by c. 20 % from 12.9 to 11.5 ka indicating increasing moisture during the YD. Millennial and centennial scale changes in δ ¹⁸O are consistent with changes in net moisture recorded in Me/Ca as well as long-term changes in ice volume. Neither orbitally induced variations in seasonal insolation or documented shifts in the ITCZ can explain the data. Changes in the meridional heat transport as a consequence of changes in thermohaline circulation explain the wetter YD. Reduced THC leads to cooler N. Atlantic and warmer/wetter Florida. Our ostracode results, which reflect climate at the same time the shell is precipitated, are consistent with pollen data from the same core (Willard et al, 2007), with a lag of 180 years. This lag is consistent with theoretical predictions that vegetation changes should lag a stepped climate event by 100-200 years.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 4924 Geochemical tracers
DE: 4938 Interhemispheric phasing
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting