Incoherency in Central American hydroclimate proxy records spanning the
last millennium
Abstract
Continued global warming is expected to result in drying of Central
America, with projections suggesting a decrease in precipitation. Poor
hindcasting of precipitation, however, due in part to spatial and
temporal limitations in instrumental data, subjects these projections to
considerable uncertainty. Paleoclimate proxy data are therefore critical
for understanding regional climate responses during times of global
climate reorganization. Here we present two lake-sediment based records
of precipitation variability in Guatemala along with a synthesis of
Central American hydroclimate records spanning the last millennium
(800-2000 CE). The synthesis reveals that regional climate responses
have been strikingly heterogeneous, even over relatively short
distances. Our analysis further suggests that shifts in the mean
position of the Intertropical Convergence Zone, which have been invoked
by numerous studies to explain variability in Central American and
circum-Caribbean proxy records, cannot alone explain the observed
pattern of hydroclimate variability. Instead, interactions between
several ocean-atmosphere processes and their disparate influences across
variable topography have resulted in complex precipitation responses.
These complexities highlight the difficulty of reconstructing past
precipitation changes across Central America and point to the need for
additional paleo-record development and analysis before the
relationships between external forcing and hydroclimate change can be
robustly determined. Such efforts should help anchor model-based
predictions of future responses to continued global warming.