Seasonal variability of temperature, salinity, and surface currents at 0° latitude section of Indonesia seas

Abstract

The Indonesian Seas are strongly influenced by the circulation system between the Pacific and the Indian Ocean, which play an important role in global circulation. In this study, an attempt is made to describe temperature, salinity, and water column stability using data obtained from the World Ocean Database (WOD), updated in 2018 at 0° latitude. The seasonal Temperature–Salinity (S-TS) were used to justify the water-mass types. The stability of the water column was analyzed based on the Brunt–Väisälä Frequency (N2). The transects were measured with depth up to 800 m and 200 km width, encompassing the Indian Ocean, Karimata Sea, Malaka Strait, Makassar Strait, Maluku Sea, Halmahera Sea, and the Pacific Ocean. Temperature and salinity profile revealed that the region in Indonesia’s eastern waters were found to have a deeper mixed layer depth (∼150 m) compared to the western waters of Indonesia (∼100 m). In the Pacific Ocean, the salinity layers were distinguishable compared to other layers. The T–S time diagram indicated the presence of six water-mass classes, including the water characteristic of the Pacific Ocean. It also shows that water mass from the Pacific Ocean more affects Indonesia seas in Southeast Monsoon. A relatively low salinity level distinguishes the water characteristics of the Karimata Strait compared to the other seas. In contrast, the Indian Ocean and Pacific Oceans, on the other hand, are more stable compared to other straits and seas along the equator transects (N2 up to 20 cycle/h). In the Northwest Monsoon, the temperature was higher compared to Southwest Monsoon. Analysis of meridional ocean currents showed a southward pattern except for Karimata Strait, which ranges from -1.5 to 1.5 m/s. The ocean currents condition found that the most energetic meridional current flows are in the Makassar Strait and affect the distribution of temperature, salinity, and stability of surface water.