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