Turbulent mixing of water masses in Selayar Slope - Southern Makassar Strait

Abstract

During the Java-Makassar-Flores (JMF) Cruise in August 2015 onboard the RV GEOMARIN 3, about 56 hydrographic CTD profiles have been acquired in the JMF confluence region of Makassar Indonesian Throughflow (ITF) and seasonal Java-Flores Current, where three intensive 24-h CTD "yoyo" measurement were carried out in Dewakang sill, Selayar slope and Kangean slope. The aim of this paper is to estimates the turbulent mixing value using Thorpe analysis, particularly in the Selayar slope - southern Makassar Strait. It is found that below surface potential density of 24.25 σθ stratification of water masses is dominated by Makassar ITF with salty (34.6 psu) North Pacific thermocline water (NPSW) and less salty (34.42 psu) North Pacific lower-thermocline water (NPIW). However, above 24.25 σθ upper NPSW is drastically dominated by much fresher water (34.17 psu) from Java Sea, where inter-leavings of salinity profiles are obviously seen between surface density of 22.0 σθ and 23.50 σθ. Estimation of turbulent vertical eddy diffusivity in this upper-thermocline are found strong with the order of 10-3 m2/s. It is suggested that energetic internal tidal waves may contribute significantly to the vertical mixing in this complex topographic region.