[A-CG43] Multi-scale ocean-atmosphere interaction in the tropics

[ACG43-11] Subsurface Ocean Conditions during Marine Heatwave Events in Southwest Sumatra

*Hanani Adiwira¹, Sayaka Yasunaka^1,2,3, Anindya Wirasatriya⁴, Toshio Suga^1,2,3 (1.Graduate School of Science, Tohoku University, Sendai, 2.Advanced Institute for Marine Ecosystem Change (WPI–AIMEC), Tohoku University, Sendai, 3.Advanced Institute for Marine Ecosystem Change (WPI–AIMEC), JAMSTEC, Yokohama, 4.Department of Oceanography, Faculty of Fisheries and Marine Science, Diponegoro University, Semarang)

Keywords:Marine heatwave, Monsoon, IOD, ENSO, Argo float

Marine heatwaves (MHWs) have been extensively studied in recent years, yet the subsurface conditions associated with these events have received less attention. Utilizing the growing availability of Argo data in Southwest Sumatra, we investigate the subsurface conditions during MHWs. Given that oceanic and atmospheric variabilities in this region are significantly influenced by the seasonal monsoon, we divided our analysis into two periods: June to November and December to May. From June to November, anomalously warm sea surface temperatures (SST) are accompanied by even higher temperature anomalies in the subsurface, extending down to a depth of 150 dbar. This subsurface warming is linked to an unusually deep thermocline. During this season, the negative Indian Ocean Dipole (IOD) is the primary driver of these warm anomalies from the surface to the subsurface. In contrast, warm SSTs are associated with anomalous cold temperatures in the subsurface from December to May, between depths of 75 to 150 dbar. This cold subsurface anomaly is associated with the uplift of the thermocline. The warm SSTs during this season are primarily due to anomalously weak winds, which result in reduced latent heat loss and less mixing with colder subsurface waters, along with large heat gain from shortwave radiation.