Assessing millennial to orbital-scale controls of Caribbean hydroclimate variability via data-model-comparisons

Tropical rainfall is conventionally linked to orbital-scale insolation variability, with higher summer insolation corresponding to stronger precipitation. Yet speleothem d18O records from the greater Mesoamerican region show opposing behaviour (Lucia et al. (2024), Li et al. (2025)), hinting at other forcing mechanisms. Here, we present a precisely dated speleothem record from Puerto Rico covering the past 234,000 years, which is compared to isotope-enabled climate model time slice simulations. By combining our new data with speleothem data from northern Brazil we create climate indeces to assess local ITCZ position and width. The data-model comparison offers the opportunity for an orbital time scale analysis, where insolation is considered for different months and latitudes. Preliminary analyses indicate that the early-rainy season might play a bigger role than previously assumed. Furthermore, millennial-scale variability strongly characterises the proxy record, which cannot be attributed to orbital forcing, but suggests a persistent sensitivity to AMOC strength (compare Warken et al. (2020)). Future work will assess, why Caribbean hydroclimate appears to be not a classical monsoon system throughout MIS 7 to 1 but rather the result of multiple factors superimposing on different timescales. References:Lucia et al. (2024). Atlantic Ocean thermal forcing of Central American rainfall over 140,000 years. Nature communications. DOI: 10.1038/s41467-024-54856-0Li et al. (2025). North Atlantic Subtropical High forcing of Atlantic Warm Pool hydroclimate variability on millennial to orbital timescales. Science Advances. DOI: 10.1126/sciadv.aea5042Warken et al. (2020). Persistent Link Between Caribbean Precipitation and Atlantic Ocean Circulation During the Last Glacial Revealed by a Speleothem Record From Puerto Rico. Paleoceanography and Paleoclimatology. DOI: 10.1029/2020PA003944