Evidence for decreased precipitation variability in the Yucatan Peninsula during the mid-Holocene

The Yucatan Peninsula (YP) has a complex hydroclimate with many proposed drivers of interannual and longer-term variability, ranging from coupled ocean-atmosphere processes to frequency of tropical cyclones. The mid-Holocene, a time of higher Northern Hemisphere summer insolation, provides an opportunity to test the relationship between Yucatan Peninsula precipitation and ocean temperature. Here we present a new, ~annually resolved speleothem record of stable isotope (δ18O and δ13C) and trace element (Mg/Ca and Sr/Ca) ratios for a section of the mid-Holocene (5.2-5.7 kyr BP), before extensive agriculture began in the region. A meter-long stalagmite from Rio Secreto, a cave system in Playa del Carmen, Mexico, was dated using U-Th geochronology and layer counting, yielding multidecadal age uncertainty (median 2SD of +/- 70 years). New proxy data were compared to an existing late Holocene stalagmite record from the same cave system, allowing us to examine changes in hydrology over time, and to paleoclimate records from the southern YP. The δ18O, δ13C and Mg/Ca data consistently indicate higher mean precipitation and lower precipitation variability during the mid-Holocene compared to the late Holocene. Despite this reduced variability, multidecadal precipitation variations were persistent in regional hydroclimate during the mid-Holocene. We therefore conclude that higher summer insolation led to increased mean precipitation and decreased precipitation variability in the northern YP, but that the region is susceptible to dry periods across climate mean states. Given projected decreases in wet season precipitation in the YP’s near future, we suggest that climate mitigation strategies emphasize drought preparation.