return
Intraseasonal, Annual, and Interannual Variabilities of Subsurface Currents at 4.7°N in the Western Pacific Ocean
May 04,2022

Zhixiang Zhang, Jianing Wang, Fan Wang, Qiang Ma

Published in Journal of Geophysical Research: Oceans, April 2022

Strong multi-timescale variabilities of subsurface zonal velocity over 300–600 m depth are observed beneath the North Equatorial Countercurrent (NECC) by the mooring observation at 4.7°N, 140°E during 2014–2018. The observed subsurface velocity shows peaks at intraseasonal, semiannual, and annual periods, and is interconnected with the El Niño-Southern Oscillation (ENSO) cycle at a nearly zero lag. Aided by a reanalysis product, we reveal mechanisms for the above variabilities. Forced by wind stress curl over 150°–155°E and 160°–170°E along 4.7°N, the vertical propagation of the third meridional mode long Rossby waves is primarily responsible for the observed semiannual and annual cycles, respectively. The subsurface intraseasonal variability with peak periods of 50- and 80-day are induced by short Rossby waves with the southeastward and downward group velocity. Such waves interconnect observed 50- and 80-day ISV of the subsurface current to that of surface currents at 8°N, 128°–130°E and 6.5°N, 132°–134°E, respectively. The ENSO variability results mainly from the interannual change of the winds that force the long Rossby waves. The wind forcing leads the Niño 3.4 index and the subsurface velocity by a similar time, resulting in the subsurface instantaneous response to ENSO.

Fig. (a) The schematic of the structure of equatorial currents in the western tropical Pacific along 140°E. The right- and left-upward-slanting lines denote eastward and westward flows, respectively. EIC, Equatorial Intermediate Current; EUC, Equatorial Undercurrent; NECC, North Equatorial Countercurrent; NESC, North Equatorial Subsurface Current; NSCC, North Subsurface Countercurrent; SEC, South Equatorial Current. The dashed red line denotes the location of our mooring. (b) Map of topography in the western tropical Pacific (color shading) and the location of the subsurface mooring at 4.7°N, 140°E (red star).

Zhang, Z., Wang, J., Wang, F., & Ma, Q. (2022). Intraseasonal, annual, and interannual variabilities of subsurface currents at 4.7°N in the western Pacific Ocean. Journal of Geophysical Research: Oceans, 127, e2021JC017969. https://doi.org/10.1029/2021JC017969

return
Copyright @ 2017 NPOCE. All Rights Reserved.