Role of BSISO on the occurrences of Marine Heatwave events over the North Bay of Bengal

Abstract

The present study investigates the properties of Marine Heatwave (MHW) events over the Bay of Bengal (BoB) during the boreal summer monsoon season. In recent decades (2001-2021), an increase in the frequency and duration of MHW events has been depicted. The rapid ocean warming primarily drives this accelerated trend in MHW events duration and is a significant concern for the scientific and fisheries communities. Tropical intraseasonal oscillations are one of the dominant modes that control the oceanic and atmospheric processes. Here, we have investigated the role of northward propagating monsoon intraseasonal oscillations (MISO) on MHW events over the north BoB during the boreal summer (monsoon season). It is found that during the break phases of MISO, enhanced shortwave radiation due to clear sky conditions triggers the MHW events. In addition, shallow mixed layer depth (MLD) also mostly favours MHW events over the north BoB during the break phases of MISO. However, during the active phases of MISO, negative SST anomalies and fewer MHW events are depicted over the north BoB. This strong relationship between shallow MLD and the occurrences of MHW events primarily indicates the connection of regional air­ sea heat flux in driving the MHW events over the north BoB. The consequences of MHW events on socioeconomic status are also projected to be extensive, severe, and persistent throughout the 21st century.