A model-based comparison of paleo-physical processes in the Bay of Bengal

Paleoclimate modeling is a demanding approach studying long-term changes in the ocean. By combining existing research and data, it can help us understand the climate of economically important areas like the Bay of Bengal (BoB). Here, we examine the seasonal and annual distributions of sea surface temperature (SST), sea surface salinity (SSS), river discharge, precipitation, wind patterns, and ice sheet extent using the outputs from Model for Interdisciplinary Research on Climate (MIROC) to investigate the changes during three major paleoclimatic periods - the Last Interglacial (LIG), Last Glacial Maximum (LGM), and Preindustrial (PI) in the BoB. A unique aspect is the focus on seasonal differences between these periods, which have not been thoroughly addressed in prior regional paleoclimate studies. The results revealed seasonal contrasts between these periods, i.e., prominent in boreal summer and fall. During the LIG, intense annual precipitation (by ~ 5 million kg m^− 2 s^− 1 more on average, compared to LGM) and increased moisture supply regulated river discharge into the bay, maintaining an average SST (~ 26.9 °C) and SSS (~ 31.4 PSU). Hemispheric cooling ensued during the LGM as ice sheets expanded, reducing moisture transport and weakening winds. This indirectly lowered SST to around 25.8 °C due to monsoon alteration and diminished river inflow. Consequently leading to an elevated SSS of approximately 33.9 PSU. Comparisons with PI conditions demonstrated mean SST reductions of approximately 0.9 °C and 1.9 °C during the LIG and LGM, respectively. SSS in the BoB was 0.7 PSU lower during LIG, but 1.37 PSU higher at LGM. In conclusion, this study underscores the profound influence of paleoclimatic changes on the SST and SSS in the BoB, thereby providing a comprehensive understanding of the climatic dynamics.