Energetic subthermocline currents observed east of Mindanao

Abstract

Abstract Two cruises of the JAMSTEC ship Kaiyo, during October 1999 and September 2000, included lowered acoustic Doppler current profiler (ADCP) measurements to 2000 m depth on zonal sections extending east from the Mindanao coast. On the second cruise, the lowered ADCP profiles were augmented by profiles to 1000 m from a 38-kHz shipboard ADCP. All zonal LADCP sections (7°N, 8°, 10°) showed southward flow along the coast extending to at least 2000 m depth. Although the Mindanao current in the upper 500 m forms a continuous narrow stream along the coast, the deeper southward flow appears to be part of a set of subthermocline eddies within 300 km of the coast; northward flow was found 100–200 km offshore during both cruises. Currents mapped by the shipboard ADCP on the second cruise indicate that cyclonic eddies were centered near 7.5°N, 128°E and 10.2°N, 127°E. Maximum speeds of 0.6 m s−1 were observed at 800 m depth on the 10°N section, and speeds of 0.2–0.3 m s−1 were found below 1500 m on all sections.