Linkages between Caribbean hydroclimate, atmospheric CO2, and methane production on orbital to millennial timescales

We present the oldest speleothem isotope record from Central America and the Caribbean, a high-resolution stalagmite (“Katún”) spanning discontinuously ∼198–322 ka BP, that documents hydroclimate variability across glacial–interglacial and millennial timescales. Katún δ 18 O covaries significantly with atmospheric CO 2 and CH 4 , and multivariate analyses show that CO 2 + CH 4 together explain more variance in δ 18 O than either gas alone. Consistent with a CO 2 -mediated SST mechanism, Katún δ 18 O correlates with tropical Atlantic and eastern Pacific SST reconstructions, indicating that radiative forcing influenced Caribbean precipitation primarily through tropical surface warming. At millennial scales, Katún δ 18 O tracks North Atlantic variability: it aligns with CH 4 peaks associated with Greenland D–O cycles and with detrital proxies of Heinrich-type ice-rafting, implicating AMOC-paced ITCZ shifts and SST-driven convection as key controls. A weak Katún–Cariaco Mo relationship highlights proxy sensitivities and argues against ITCZ migration as the sole driver. In contrast to Asian monsoon archives, Katún shows little precessional insolation imprint, emphasizing the dominance of internal ocean–atmosphere dynamics (AMOC, SSTs) in regulating Caribbean hydroclimate and modulating tropical wetland methane emissions during MIS 7–9. • A new stalagmite (MIS 7–9) from the Yucatan Peninsula was analyzed. • CO 2 drives Caribbean hydroclimate via tropical SST on orbital timescales. • Millennial Caribbean hydroclimate shifts reflect AMOC strength and ITCZ movement. • Global methane variability ties to rainfall-driven tropical wetlands production.