SYNCHRONOUS THERMOCLINE DYNAMICS ACROSS THE EQUATORIAL INDIAN AND PACIFIC INFERRED FROM MULTISPECIES FORAMINIFERAL ANALYSES

Circulation from the tropics is vital in balancing the distribution of heat in the global oceans and regulating the dynamics of climate. Warm-water carbonate platforms acts as the natural repository of biogeochemical cycles and sea-level fluctuations through the continuous deposition of calcareous and detrital sediments. Following drilling by the International Ocean Discovery Program (IODP) Expedition 359, Maldives Monsoon and Sea Level, at Site U1467, we present high-resolution stable isotope records of four planktonic foraminifera species (Globigerinoides ruber, Globigerinoides sacculifer (w/o sac), Neogloboquadrina dutertrei, and Globorotalia menardii) to monitor changes in the ventilation, nutrients, and thermal profile of the Maldivian Inner Seaway. This record spans from Marine Isotope Stage (MIS) 6 to the Holocene, and reveals δ¹³C gradient collapses of all four species at Termination II and the Last Glacial Maximum (LGM)/Termination I. Interestingly, these δ¹³C collapses and minima are seen in the exact same species in the eastern equatorial Pacific (EEP) from core TR163-19 (Spero et al., 2003). Sub-Antarctic Mode Water or Antarctic Intermediate Water (SAMW/AAIW) would have propagated ¹²C rich, well-mixed lower circumpolar water into both Pacific and Indian basins during these glacial intervals (Ninnemann and Charles, 1997; Spero and Lea, 2002). At the same time, the δ¹³C minima could be explained by increased CO₂ invasion from the atmosphere south of the Subtropical convergence zone where SAMW and AAIW are down-welled (Lynch-Stieglitz et al., 1996). Regardless, these similar records indicate synchronous thermocline dynamics across two basins fed by a Southern Ocean source that could also be recorded in the carbonate banks in the equatorial Atlantic Ocean.