Physical Oceanography Condition and the Turbulent Mixing in Mid-upper Layer of the Eastern Indian Ocean during the InaPRIMA Cruise 2019

Abstract

Abstract Turbulent mixing in the ocean has a significant role in weather and climate, especially concerning flux between the ocean and atmosphere. This research aims to study physical oceanography conditions and quantify the turbulent mixing in the Eastern Indian Ocean during the InaPRIMA cruise in November 2019. The CTD data from five meridional stations were processed to determine the oceanographic condition. Water mass stratification was determined by a temperature gradient of 0.05°C/m for thermocline boundaries, and turbulent mixing was calculate using the Thorpe method. The results showed that the mixed layer depth (MLD) varied between 16.41-45.74 m, while the depth of the thermocline layer ranged from 178.3-237.0 m. The MLD was getting deeper to the north, while thermocline depth tends to be shallower associated with the wind speed. The Thorpe analysis for all CTD showed that overturn with size varies between 2.5-30 m was identified. The turbulent kinetic energy was ranged from an order of 10−8 to 10−6 Wkg−1, while the turbulent diffusivity was ranged from an order of 10−4 to 10−2 m2s−1. Turbulence mixing in MLD suggests driving by wind stress, while in thermocline because of shear instability and double-diffusive salt fingering and in deep layer because of topography.