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A continuous 100 thousand-year stalagmite δ18O record from the Yucatan Peninsula: implications for Caribbean hydroclimate on orbital and millennial timescales




Hill, Morgan

Type of Degree

Master's Thesis




I 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 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 periodicities between 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 on millennial timescales 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.