GREENHOUSE GASES AND HYDROCLIMATE VARIABILITY IN THE CARIBBEAN: A NEW SPELEOTHEM RECORD SHEDDING LIGHT ON MILLENNIAL AND ORBITAL-SCALE CHANGES

• Main Author: Zhang, Meilun
• Format: Text
• Language: unknown
• Published: ScholarWorks@UMass Amherst 2023
• Subjects: Paleoclimate; Speleothem; Stable isotope; Caribbean; Earth Sciences; Geochemistry; Speleology; Greenland; North Atlantic
• Online Access: https://scholarworks.umass.edu/masters_theses_2/1355; https://doi.org/10.7275/35736669.0; https://scholarworks.umass.edu/context/masters_theses_2/article/2404/viewcontent/Thesis_MeilunZhang_final.pdf

Hydroclimate evolution in the northern Caribbean region has been investigated by several studies, but they offer contradicting results and none of them cover a full glacial-interglacial transition to examine orbital climate forcing. Here we present refined U-Th dating and oxygen isotope (δ18O) data from a stalagmite named Katún collected from Rio Secreto cave in the Yucatan Peninsula that discontinuously spans the time interval between 198 thousand years (kyr) before present (BP) to 320 kyr BP. Stalagmite δ18O is interpreted to reflect precipitation amount variability as established by previous studies from this cave. On orbital timescales, we identified marine isotope stages (MIS) 7, 8, and 9 in the Katún stalagmite δ18O record. The average stalagmite δ18O value during MIS 7 and 9 interglacial intervals is ~-4.5‰, suggesting wetter conditions than the glacial MIS 8 with an average δ18O value of ~-3‰. The stalagmite δ18O record exhibits higher amplitude δ18O and thus precipitation variability, and an increase in the frequency and intensity of drought events during the drier glacial interval. The record suggests a strong link between atmospheric greenhouse gases, CO2 andCH4, and precipitation variability in the Caribbean, which affects hydroclimate via changes in tropical Atlantic sea surface and air temperature. We propose that changes in North Atlantic high latitude climate are connected to regional hydroclimate, as evidenced by concurrent Caribbean precipitation and atmospheric methane variability, similar to Greenland D-O events. The broader implication of this study is that human activities may alter the fundamental relationship between Caribbean hydroclimate and greenhouse gases, which have likely sustained tropical wetlands and modulated methane production for millennia.