Investigating Caribbean hydroclimate variability on orbital and millennial timescales using a 100 thousand-year stalagmite δ18O record from the Yucatan Peninsula

Hydroclimate evolution in the northern Caribbean region has been investigated by several studies, but they offer contradicting results and none of them cover a full glacial-interglacial transition to examine orbital climate forcing. Here we present refined U-Th dating and oxygen isotope (δ18O) data from a previously-reported stalagmite named Katun (Hill et al., AGU Fall meeting 2019), collected from Rio Secreto cave in the Yucatan Peninsula that discontinuously spans 198 kyr BP to 320 kyr BP. Stalagmite δ18O is interpreted to reflect precipitation amount variability as established by previous studies from this cave. On orbital timescales, we identified marine isotope stages (MIS) 7, 8, and 9 in the Katun stalagmite δ18O record. The average stalagmite δ18O value during MIS 7 and 9 interglacial intervals is ~-4.5‰, suggesting wetter conditions than the glacial MIS 8 with an average δ18O value of ~-3‰. The stalagmite δ18O record exhibits higher amplitude δ18O and thus precipitation variability, and an increase in the frequency and intensity of drought events during the drier glacial interval. Overall, Katun δ18O closely tracks Caribbean sea surface temperatures (SST) and atmospheric CO2 levels, suggesting that glacial-interglacial precipitation variability in the broad Caribbean region may have been controlled by greenhouse forcing, via its effect on tropical Atlantic SST variability and the position of the Intertropical Convergence Zone (ITCZ). On millennial timescales, Katun δ18O shows pronounced oscillations with an average period of 6 kyr. The amplitude variability of these δ18O oscillations is ~2.5‰, larger than observed in any other speleothem record from the Caribbean covering the last glacial cycle. We observed a strong correspondence between the Katun δ18O record and the Antarctic Dome C ice core methane record, which is the closest proxy record available for Greenland temperature changes preceding the last interglacial. We suggest that Katun δ18O millennial oscillations reflect Greenland Dansgaard-Oeschger events (D/O) through shifts in the ITCZ position associated with Atlantic Meridional Overturning Circulation changes. Our results reveal that the controlling effect of D/O events on tropical Atlantic hydroclimate was present beyond the last glacial cycle.