Wednesday, 8 October 2008: 2:15 PM
George R. Brown Convention Center, 310BE
A stalagmite collected from BRC Cave in west-central Florida was deposited from 29ky to 21ky BP, encompassing Heinrich Event 2 (H2), and from 5ky to 4ky BP, during the mid-Holocene. The timing of H2 in our record is ~24ky BP, which is temporally similar to its timing in other areas worldwide. However, the oxygen and carbon isotope values indicate the climate in Florida was warm and wet, rather than cool and dry like many other regions, with more precipitation and a shift from savannah to forest during this period. One possible cause is the shutdown of the North Atlantic Conveyor Belt due to increased glacial meltwater input, thereby preventing heat transfer by the Gulf Stream from the subtropics/tropics to the northerly latitudes. This mechanism would allow for an increase in convective thunderstorm activity due to higher evaporation rates.
In contrast to the H2 event, during the mid-Holocene the speleothem oxygen isotopes show a ~2‰ shift, indicating higher precipitation amounts than the glacial period. Additionally, the carbon isotopes show a ~3‰ shift towards more negative values, indicating more heavily forested conditions during that time. The speleothem isotopes during the mid-Holocene reflect a warmer and wetter environment than the end of the glacial period. The preliminary data support the possibility of atmospheric teleconnections between the tropics/subtropics and northerly latitudes playing a major role in controlling climate change in Florida. Possible causes include changes in the migration pattern of the Intertropical Convergence Zone and the influence of El Nino on Florida's winter precipitation.