NOAA/WDS Paleoclimatology - Lake Izabal, Guatemala Hydrogen Isotope and XRF Spectroscopy Data over the past 1,200 years

Central American precipitation is vital to agricultural and economic stability, but poorly constrained past hydroclimate variability limits future forecasts. Here, we reconstruct 1,200 years of precipitation and atmospheric circulation from sedimentary plant wax hydrogen isotope ratios and XRF spectroscopy from Lake Izabal, Guatemala. Warm intervals, (e.g., the Medieval Climate Anomaly; MCA), were dry with 2H-depleted precipitation, whereas the cooler Little Ice Age (LIA) was wetter and precipitation was 2H-enriched – opposite to the conventional “amount effect.” We attribute this to shifts in dominant moisture sources. Specifically, during the MCA, the Intertropical Convergence Zone (ITCZ) was in a northern position, while the Caribbean Low-Level Jet (CLLJ) strengthened and shifted south, reducing 2H-enriched Caribbean input while increasing 2H-depleted Pacific-sourced moisture. During the LIA, a northern CLLJ and southern ITCZ enhanced Caribbean-sourced precipitation. Our results highlight that Atlantic-Pacific moisture-source balance exerts a primary control on regional isotopic signatures that can be reconstructed using isotopic proxies.