Estimation of mixed layer depth from argo float data in Makassar strait during el ni o southern oscilation

Abstract

Makassar Strait is a pathway of water mass passing trough from the Pacific Ocean to the Indian Ocean. Makassar Strait is also one of the waters in Indonesia which passed by Indonesian Throughflow (ITF). Movement of water masses due to the ITF, wind system, and complex bathymetry conditions will cause the movement of vertical water masses (mixing). This makes the upper layers homogeneous, the objective of this study is to assess the variation of MLD using Argo Float data adjusted for ENSO (El Ni o Southern Oscilation) events, under El Ni o, La Ni a, and normal conditions. MLD determination using temperature gradient criterion with value ≤ 0,1 oC/m. The data processing using Ocean Data View 5.0.0 software shows that the depth of homogeneous layer in Makassar Strait waters during El Ni o years is various, between 37,73 - 73,62 m with temperature 25,7 - 28,99 oC. During La Ni a, MLD found varying around 30,59 - 97,89 m with temperature profile slightly colder (26,7 - 29,8 oC). And during normal year, MLD located around 28,55 m to 112,98 m, shallowest and deepest from all data set, respectively. Average value of MLD in is vaguely normal deeper than La Ni a and El Ni o condition, as it should be shallower, showed that temperature gradient criterion with value ≤ 0,1 oC/m is not quite good to determine the MLD layer in Makassar Strait.