A NEW HIGH-RESOLUTION SPELEOTHEM RECORD OF LATE PLEISTOCENE TROPICAL CLIMATE FROM THE YUCATAN PENINSULA, MEXICO

Climate records from the Yucatan Peninsula spanning glacial-interglacial time scales are currently unavailable; it is therefore impossible to assess whether the region experienced hydrological changes on orbital and millennial times scales. A stalagmite (named Katún) retrieved from a limestone cave system located on the northeastern Yucatan Peninsula in Mexico provides the first high-resolution (37 years) oxygen isotope (δ¹⁸O) record spanning the interval between 96.9 ky and 85.7 ky before present. The chronology of the Katún stalagmite δ¹⁸O record is based on six absolute U-Th dates. Katún stalagmite δ¹⁸O values range from -6‰ to -2‰ and average -4.5‰, close to the expected value at isotopic equilibrium with modern drip water δ¹⁸O. The δ¹⁸O composition of tropical speleothems has been found to reflect the amount effect on seasonal and interannual time scales (Vuille et al. 2003). The regional hydrologic cycle of the Yucatan Peninsula has been linked to the position and intensity of the Intertropical Convergence Zone (ITCZ), the strength of the Caribbean Low-Level Jet (CLLJ) (Vuille et al. 2003, Mestas-Nuñez 2008), and tropical Atlantic cyclogenesis. The stalagmite δ¹⁸O record offers a means of investigating tropical North American hydrological shifts and their potential drivers on centennial and longer time scales. Preliminary results suggest that the Yucatan Peninsula became progressively drier from ~90 ky to 86 ky before present during the transition between marine isotope stages (MIS) 5b and 5a in sea level records. A comparison between the stalagmite δ¹⁸O record and the North Greenland Ice Core Project temperature record suggests that this drying trend was coeval with northern hemisphere high latitude cooling associated with the transition from Daansgard-Oeschger events 22 to 21. The Katún stalagmite offers the first evidence of glacial hydrological responses of the Yucatan Peninsula to rapid shifts in climate on millennial time scales.