Open AccessMindanao Current and Undercurrent: Thermohaline Structure and Transport from Repeat Glider Observations
Author(s) -
Martha Schönau,
Daniel L. Rudnick
Publication year - 2017
Publication title -
journal of physical oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.706
H-Index - 143
eISSN - 1520-0485
pISSN - 0022-3670
DOI - 10.1175/jpo-d-16-0274.1
Subject(s) - thermocline , geology , boundary current , thermohaline circulation , oceanography , water mass , salinity , argo , climatology , ekman transport , current (fluid) , eddy , antarctic intermediate water , upwelling , ocean current , turbulence , north atlantic deep water , geography , meteorology
Autonomous underwater Spray gliders made repeat transects of the Mindanao Current (MC), a low-latitude western boundary current in the western tropical North Pacific Ocean, from September 2009 to October 2013. In the thermocline ( 26 kg m −3 ), a persistent Mindanao Undercurrent (MUC), with a velocity core of 0.2 m s −1 and mean net transport, flows poleward. Mean transport and standard deviation integrated from the coast to 130°E is −19 ± 3.1 Sv (1 Sv ≡ 10 6 m 3 s −1 ) in the thermocline and −3 ± 12 Sv in the subthermocline. Subthermocline transport has an inverse linear relationship with the Niño-3.4 index and is the primary influence of total transport variability. Interannual anomalies during El Niño are greater than the annual cycle for sea surface salinity and thermocline depth. Water masses transported by the MC/MUC are identified by subsurface salinity extrema and are on isopycnals that have increased finescale salinity variance (spice variance) from eddy stirring. The MC/MUC spice variance is smaller in the thermocline and greater in the subthermocline when compared to the North Equatorial Current and its undercurrents.