SUBTROPICAL CLIMATIC RECORD OF THE LAST DEGLACIATION FROM FLORIDA

We examine the timing and magnitude of floral change near Tampa Bay, Florida during the last deglaciation using radiocarbon-dated sediment core MD02-2579 that has decadal to sub-decadal temporal resolution between ~21 ka and ~11.4 ka. This core provides a record of subtropical ecosystem response to the Bölling/Allerød, Older Dryas, IntraAllerød Cold Period, and Younger Dryas climate events correlative with those from high- and low-latitude sites elsewhere in the Northern Hemisphere.

Between ~21 ka and ~17 ka, pollen assemblages indicate wetland habitats, primarily fed by groundwater, during an interval of reduced precipitation relative to today. Abundant Carya (hickory) pollen during this interval indicates persistence of winter temperatures 3˚ to 4˚ C cooler than today. The initial deglaciation began ~17.1 ka and is marked by increased abundance of Pinus (pine) pollen and a shift to lacustrine conditions. Throughout the Bölling/Allerød interstadials (14.7 – 12.9 ka), Pinus pollen reached nearly modern levels, but several centennial-scale peaks in abundance of Chenopodiaceae/Amaranthaceae (pigweeds, water hemp) pollen occur throughout the deglaciation: ~14.9 ka (Oldest Dryas), ~14.1 ka (Older Dryas), ~13.7 ka, and ~13.1 ka (IntraAllerød Cold Period). The Younger Dryas stadial (12.9 – 11.4 ka) also is characterized by high percentages of Chenopodiaceae/Amaranthaceae pollen and increased organic content of sediments consistent with expansion of wetland habitats.

Our results indicate: 1) the deglacial warming began ~17 ka, accompanied by increased precipitation; 2) further warming and increased precipitation occurred during the Bölling/Allerød interstadials; and 3) rapid shifts to drier conditions during the Younger Dryas and other stadials are in phase with other high- and low-latitude paleoclimate records from the Northern Hemisphere.