Impact of Ocean Warming on Marine Heatwaves Characteristics in the Bay of Bengal

Extremely warm oceanic conditions, known as Marine Heatwaves (MHWs), in the Bay of Bengal, influence monsoon rainfall and cyclones; and are linked to climatic modes. These MHWs are a result of a combination of long-term ocean warming and physical processes. In this study, we segregated this impact of long-term ocean warming, from the physical processes, to understand how long-term warming influence the MHW characteristics, by a detrending baseline approach. This approach works by removing the long-term linear trend from the temperature data, which is then used to detect MHWs. We used the Ocean Reanalysis System 5 (ORAS5) dataset in this study over the period of 1993–2020, which shows good agreement with the OISST and RAMA observation on detecting the MHWs characteristics at the upper ocean. The regions with high warming tendencies showed a smaller number of the MHWs events (1-2 events at the surface) under the warming scenario but with more intensity and duration (10-20 days per event). The spatial movement of these MHWs are seen to be accompanied by western boundary currents during spring (March–May). The westward movement of the MHWs are associated with eddies during other seasons. This study helps us understand how long-term warming puts more stress on marine ecosystems.