HR: 1340h
AN: PP13A-0595    [Abstracts]
TI: High-Resolution Pollen Record of Deglacial Climate Variability in Central Florida
AU: * Willard, D A
EM: dwillard@usgs.gov
AF: U.S. Geological Survey, 926A National Center, Reston, VA 20192 United States
AU: Bernhardt, C E
EM: cbernhardt@usgs.gov
AF: U.S. Geological Survey, 926A National Center, Reston, VA 20192 United States
AU: Edgar, T
EM: tdegar@usgs.gov
AF: U.S. Geological Survey, 600 4th Street South, St. Petersburg, FL 33701 United States
AB: Pollen evidence from lacustrine sediments in Tampa Bay, Florida document considerable climatic variability superimposed on deglacial warming in the subtropics. Nine radiocarbon dates on well-preserved mollusk shells provide a reliable chronology of continuous sedimentation from 20 ka to 11.5 ka; examination of pollen assemblages from 2 cm increments within the lacustrine unit provide temporal resolution averaging one sample every 45 years. During the glacial maximum, much drier and cooler than modern conditions are indicated by pollen assemblages enriched in Chenopodiaceae, {\it Carya}, Poaceae and {\it Ambrosia}. Increased abundance of {\it Pinus} pollen between 17.4 ka and 15 ka indicates the existence of warmer, wetter conditions in the interval including Heinrich Event 1. After a reversion to drier, cooler conditions at about 15 ka, {\it Pinus} pollen abundance increased again at 14 ka. Combined with the near loss of {\it Carya} pollen, these data suggest attainment of nearly modern climatic conditions during the Bolling-Allerod (14-13 ka). However, variability within the Bolling-Allerod is documented by shifts to deglacial-equivalent vegetation during the Older Dryas (13.4-13.6 ka). The Younger Dryas (12.9-11.6 ka) is characterized by two distinct phases: from 12.9-11.9 ka, the increased abundance of Chenopodiaceae and {\it Quercus} mark drier, possibly cooler conditions comparable to those of the deglacial (17.4 - 14 ka). From 11.9-11.5 ka, strong dominance of herbaceous Chenopodiaceae is similar to full-glacial conditions, indicating much drier, possibly cooler conditions. Comparison of these paleoclimatic patterns with marine records from Orca Basin in the Gulf of Mexico indicate close temporal correspondence in warming of atmospheric and sea-surface temperatures. Pollen evidence also suggests that significant warming began around 17.4 ka, before the onset of Heinrich Event 1, as has been documented at other sites in the North Atlantic Ocean and Europe. This record of deglacial atmospheric temperature and moisture variability provides an opportunity to evaluate the relative influences of meltwater flows, thermohaline circulation, and atmospheric circulation on climate variability in the subtropical Atlantic Ocean.
DE: 4815 Ecosystems, structure and dynamics
DE: 3309 Climatology (1620)
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting