Sea surface conditions in the Bay of Bengal since the early Pliocene

There is uncertainty in how future climate change will affect the variability and intensity of the Asian Monsoon System which affects over a billion of Southeast Asia’s inhabitants. Modern CO₂ concentrations have reached 410 ppm, a level not experienced since the early Pliocene (3.5 - 5 Ma). Although the Pliocene is not a direct analog to future climate change, it presents an opportunity to study how monsoon systems have responded to past times of global warmth and through climate transitions.

The early Pliocene is characterized by global average temperature 3-4°C warmer than today, 3-7°C higher sea surface temperatures (SST) in the eastern Atlantic & Pacific Ocean, stable SST’s in the Pacific warm pool, and a deepening of the thermocline basin wide. The expanded Indo Pacific Warm Pool (IPWP) resulted in reduced zonal and meridional SST gradients. There is currently little data from the Indian Ocean through the last 6 Ma, and developing a long-term SST record in the Indian Ocean will expand our understanding of the links between Indian Ocean variability and monsoon systems.

We will present foraminifera paleoclimate records from IODP Site U1451 (8°N, 88°E in 3607m water depth) in the Bay of Bengal. The top 200 m of Site U1451 is mostly hemipelagic calcareous clay (foraminifera-rich clay), and represents the last 6 Ma. The core was sampled at 0.4 m intervals in calcareous clay sections and 2 m intervals in sandy turbidite sections, totaling 244 samples and leading to a low resolution (~20-30 ka) record. We picked ~ 30 G. sacculifer, 30 G. ruber, and 15 G. tumida from two size fractions (250-355 and 355-425 μm). Samples will undergo standard reductive and oxidative cleaning procedure before Mg/Ca is measured on an ICP-OES. These Mg/Ca temperature records will be the first long-term paleoceanographic reconstructions in the Indian Ocean. This study will improve our understanding of the connection between the Indian Ocean and the monsoons through the last 6 Ma while simultaneously providing insight as the role of IPWP in global climate change.