North Atlantic Subtropical High forcing of Atlantic Warm Pool hydroclimate variability on millennial to orbital...

Orbital-scale variations in insolation are widely considered to drive tropical and monsoonal rainfall, with higher summer insolation linked to stronger precipitation. Here, we present a precisely dated speleothem record from Cuba that reconstructs Atlantic Warm Pool (AWP) hydroclimate over the past 129,000 years and challenges this paradigm. Instead, we identify a previously unrecognized link between AWP hydroclimate and the North Atlantic Subtropical High (NASH) operating on millennial to orbital timescales. During intervals of high summer insolation coupled with cooler tropical North Atlantic sea surface temperatures (SSTs), NASH strengthens and expands westward, reducing rainfall across the AWP. This SST-NASH coupling amplified precessional-scale hydroclimate variability between 130 and 60 ka, when insolation amplitude was nearly twice that of the 60- to 12-ka interval. Our data further show that particularly strong insolation peaks at 105 and 126 ka caused pronounced westward NASH expansion, triggering two extreme dry events, similar to the process observed during modern midsummer dry spells.