[A-OS12] Physical, biogeochemical, and ecological processes and variability in the Indian Ocean

[AOS12-02] Low salinity water and mixed layer variability in the regions of Indonesian Throughflow (ITF) exits of the eastern Indian Ocean

*Takanori Horii¹, Tengfei Xu², Iwao Ueki¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.The First Institute of Oceanography, Ministry of Natural Resources, China)

Keywords:Indonesian Throughflow (ITF), eastern Indian Ocean, Indonesian Archipelago, ocean mixed layer

The Indonesian Throughflow (ITF) flows from the Pacific Ocean through the Indonesian Archipelago and into the eastern Indian Ocean. It is an important element of the global ocean circulation. Since the 2000s, there has been dramatic progress in quantifying ocean circulation associated with the ITF. On the other hand, it is not clear how the warm and low-salinity water masses of the ITF entering the eastern Indian Ocean affect the ocean condition and possibly alter the processes of heat exchange in the upper ocean.
This study aims to investigate the possible impact of low salinity water of the ITF on the hydrographic condition of the eastern Indian Ocean. Based on observations from Argo floats and CTD observations around the Sunda and Lombok Straits, we found a distribution of upper-layer low salinity waters and shallow mixed layers associated with the ITF. In general, the mixed layer depth in the southeast Indian Ocean is shallow during the northwest monsoon (December-March) and deep during the southeast monsoon (June-October). In the regions around ITF exits, however, water masses with shallow mixed layers were frequently observed from August to October. Possible changes in the air-sea heat exchange processes related to these water masses and mixed layer changes will be discussed.