Geochemical evidence of drying during the 4.2 ka event in sediment cores from the Yucatán Peninsula, Mexico

Abstract

Tropical hydroclimate variability during the Middle and Late Holocene was investigated using geochemical indicators of local-scale precipitation and evaporation preserved in sediment cores from two sites in the Mexican Yucatán Peninsula. Scanning X-Ray fluorescence spectroscopy data show generally decreasing precipitation trends during the Early and Middle Holocene. During the transition between the Middle and Late Holocene, geochemical evidence of reduced watershed erosion and increased evaporation indicate that a centennial-scale drying event impacted the region between 4.3 and 4.0 ka (kilo-anum; thousand years before present). These findings suggest that the 4.2 ka drying event, which has been previously recorded in Europe, Asia, and North and South America, also impacted the northern Neotropics. A comparison between our data and existing regional hydroclimate records suggests that dry conditions during the 4.2 ka event were coherent across western Central America. The timing of these regionally dry conditions coincided with a reduction in zonal sea surface temperature gradients in the tropical Pacific Ocean and a consequent mean-state increase in the frequency of El Niño events, suggesting that linkages between Pacific Ocean-atmosphere dynamics played a significant role in the regional drying that occurred during that time. These data provide new support for a Central American expression of the 4.2 ka event, evidence for which is currently rare.