Graduation Year

2005

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Geology

Major Professor

Philip van Beynen.

Keywords

Paleoclimate, Stalagmites, Stable isotopes, Uranium-series, Teleconnections

Abstract

Little is known about the paleo-precipitation of the Florida Peninsula. In order to better understand Floridas late Holocene climate variability (last 4,200 years), the isotopic composition was analyzed of four speleothems from two caves, in West-Central Florida. Two speleothems were collected from BRC Cave in Hernando County, and two others from Briar Cave in Marion County. This study represents the first speleothem-based paleoclimate records for Florida. Uranium-series disequilibrium analyses were determined by using thermal ionization mass spectrometry (TIMS) to provide accurate determination of chronology of the deposition of the speleothems.

Stable isotopic analyses of oxygen and carbon were performed using stable isotope mass spectrometry, which provided information regarding changing amounts of precipitation (increase in precipitation, decrease in the and#61540;18Oc) and types of vegetation above the cave (increased forest density, decrease in the and#61540;13Cc). Variations in the speleothems and#61540;18O composition reveal abrupt changes in precipitation amount, fluctuations that appear both regional and hemispheric in nature. Strong similarities between the speleothem and#61540;18O, Lake Tulaneand#61472;and#61540;D record (Cross et al. 2003; 2004) and the SE US tree-ring record (surrogate for spring precipitation - Stahle and Cleaveland 1992) suggests a regional atmospheric influence on Floridas precipitation.

The major causes of changes in precipitation are proposed to be Atlantic Multi-decadal Oscillation (AMO), El Nino and changes in the relative positions of the Intertropical Convergence Zone (ITCZ)-North Atlantic High (NAH). Comparison between the and#61540;18Oc and surrogates of these influences, show all three have some effect. AMO and El Nino have short-term (decadal) influence and ITCZ-NAH has a long term (centennial) influence. The contributions of these climatic effects have implications for teleconnections involving Floridas climate; the AMO correlation shows higher latitude influence, while El Nino and the ITCZ show tropical influence on subtropical Florida.

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