Late Glacial to early Holocene hydroclimate and environmental changes in northern Central America coupled to upstream regional monsoon convection

Tropical oxygen isotope (δ18O) records from terrestrial archives such as speleothems have been commonly interpreted as proxies for regional-scale rainfall because δ18O of precipitation is inversely related to the amount of upstream rainout. However, speleothem δ18O values can be decoupled from local rainfall amount at the study site, highlighting the need for local rainfall-sensitive proxies. Here we combine previously published oxygen records with carbon and uranium isotope data from four replicated, precisely dated stalagmites from Guatemala to show that local rainfall at our study site has been tightly coupled with regional upstream Caribbean atmospheric dynamics over the last deglaciation and the Holocene (18,000−4000 yr B.P.). Reduced local rainfall and diminished soil and vegetation activity coincide with widespread weakening of upstream regional convection during Heinrich Stadial 1 and the Younger Dryas. In contrast, strong regional convection aligns with enhanced local wetness during the Bølling-Allerød warm period and the early Holocene. Our multiproxy record, supported by isotope-enabled model simulations, demonstrates a strong sensitivity of local hydroclimate to changes in upstream regional monsoonal convection across Central America and the Caribbean. Furthermore, persistently low δ13C values during the cold and dry HS1 and YD intervals suggest that C3 vegetation likely remained dominant in the Guatemala highlands throughout the deglacial period. Our analysis shows that changes in regional atmospheric circulation strongly influence local hydrology and environmental processes in northern Central America and provides new climatic context for assessing past (and potentially future) ecosystem and biodiversity responses to rapid climate changes.