Observations of the low latitude western boundary currents in 2017

Abstract

Field observations including deployment of ADCP moorings and satellite-tracked surface drifters using the R/V Isabu were carried out in the southern Philippine Sea in November and December of 2017 to observe the low latitude western boundary currents. The velocity data measured by lowered ADCP and vessel mounted ADCP clearly show the Mindanao Current (MC) with a maximum speed > 1 m/s and the Mindanao Undercurrent with a maximum speed > 0.5 m/s. The strong southward flow nearthe sea surface appeared in the area from the Philippine coast to 129°E along 8°N. Both geostrophic velocity and LADCP data indicate that the current thickness exceeds 2000 m. Drifter trajectories revealed the Mindanao Eddy (ME) and Halmahera Eddy in the MC and the New Guinea Coastal Current retroflection area, respectively, in the 2017-2018 winter season. The result with other drifter trajectories support the possible seasonal displacement of the ME in the meridional direction.