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

Abstract

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 δ18O covaries significantly with atmospheric CO2 and CH4, and multivariate analyses show that CO2 + CH4 together explain more variance in δ18O than either gas alone. Consistent with a CO2-mediated SST mechanism, Katún δ18O 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 δ18O tracks North Atlantic variability: it aligns with CH4 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.This project was supported by M. Medina-Elizalde and S. Burns P2C2 NSF Grant # 2102983. U-Th dating was partially supported by grants from the National Science and Technology Council, Taiwan (111-2116-M-002-022-MY3), the National Taiwan University, Taiwan (112L894202), and the Higher Education Sprout Project of the Ministry of Education, Taiwan (110L901001 and 110L8907)