A mid-Holocene paleoprecipitation record from Belize

Understanding past climate may contribute to a better understanding of future climate change, allowing for adaptations to changing water resources. High latitude paleoclimate reconstructions reveal a warmer northern hemisphere during the mid-Holocene, yet paleoclimate records from tropical Central America are lacking, especially seasonally resolved reconstructions needed to resolve seasonal shifts. Here we reconstruct mid-Holocene precipitation using high-resolution (sub-annual to biannual) stable isotope ratios (oxygen and carbon) extracted from a speleothem recovered from Belize to investigate the frequency and magnitude of precipitation variability. We found a slight increase in precipitation during the mid-Holocene in Belize with less variability compared to the late-Holocene. This increase in precipitation may be a result of the expansion of the North Atlantic Subtropical High (NASH), which strengthens the Caribbean Lower Level Jet, enhancing westward advection of atmospheric moisture to Belize. The decrease in precipitation variability could be derived from a northward movement of the Intertropical Convergence Zone (ITCZ) placing Belize within the bounds of the ITCZ for a longer period each year. Time series analysis reveals periodicities of 200-250 years which correspond to the Suess solar cycle. The additional periods of ~ 100 and ~ 50 years also have origins in solar irradiance. The North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Variability (AMV; also known as the Atlantic Multidecadal Oscillation (AMO)), long recognized as important drivers of precipitation variability in the region, are present but only at the 90% significance level. We posit that the reduced influence of the NAO and AMV could be caused by the northerly migration of the ITCZ during the mid-Holocene.