Investigating Meridional Structure of North Equatorial Current and Equatorial Under Current During Indonesia PRIMA Cruise 2017

Equatorial currents consisting of the North Equatorial Current (NEC) and Equatorial Under Current (EUC) play a significant role in the dynamics of the Indian Ocean with waters west of Sumatra. This article examines the water masses in the eastern Indian Ocean and the dynamics of the surface equatorial current at 90° BT longitude from 2° LS to 2° LU on March 1–3, 2017, as part of the Indonesia Prima 2017 expedition. NEC was detected at a depth of 5–75 m with a speed of 0–0.5 m/s to the west. EUC was detected at a depth of 75–170 m with a speed of 0.25–0.85 m/s to the east. The results of data analysis of temperature, salinity, and density indicate the intake of high-salinity water masses from the southern Indian Ocean, namely South Indian Central Water (SICW), which has a temperature range of 8.0–25.01 °C and salinity values of 34.6–35.2 PSU. SICW is carried by SEC. The movement of SEC during this study has a characteristic tendency to be asymmetrically stronger toward the north of the equator. The heat transported by the NEC is − 0.0215 PW (toward the Indian Ocean) and the EUC is 0.0347 PW (toward the west of Sumatra). There is added heat transport to the west of Sumatra by 0.0132 PW so that the thermocline layer thickens.