A CONTINUOUS 100 THOUSAND-YEAR STALAGMITE Δ18O RECORD FROM THE YUCATAN PENINSULA: IMPLICATIONS FOR CARIBBEAN HYDROCLIMATE ON ORBITAL AND MILLENNIAL TIMESCALES

We present a new stalagmite δ¹⁸O record, named Katún, collected from Río Secreto Natural Reserve in the Yucatan Peninsula (YP) that spans the interval between 198 kyr to 320 kyr before present (BP), thus offering the oldest continuous terrestrial paleoclimate record from the tropical Americas. The Katún δ¹⁸O record is interpreted to reflect precipitation amount based on modern observations and isotopic equilibrium calculations. On orbital timescales, the Katún δ¹⁸O record shows the general features observed in atmospheric CO2, tropical SSTs, and benthic foraminiferal δ¹⁸O records. Specifically, marine isotope stages (MIS) 7, 8, and 9 are readily identifiable in the stalagmite δ¹⁸O record. The Katún δ¹⁸O record suggests humid conditions and low amplitude precipitation variability during MIS 7 and 9 interglacial intervals, coeval with high tropical sea surface temperatures (SST) and high atmospheric CO2. During glacial inceptions after MIS 9 and 7, the Katún δ18O record suggests high amplitude precipitation variability and an increase in the frequency and intensity of drought events. Dominant periods of variability at 4-8 kyr in the Katún δ¹⁸O record resemble millennial scale climate variability seen in Greenland ice core δ¹⁸O records from the last glacial. We suggest that glacial-interglacial precipitation variability in the broad Caribbean region reflects atmospheric greenhouse forcing via its effect on tropical Atlantic SST variability. In addition, we propose that Caribbean precipitation millennial scale variability reflects shifts in the intensity and position of the Intertropical Convergence Zone (ITCZ) in association with Atlantic Meridional Overturning Circulation (AMOC) changes, as hypothesized for the last glacial interval.