Meeting the Mindanao and the Kuroshio currents

Lively data, November 23, 2009

Maps of Geostrophic Velocities Anomalies (in cm/s) on the eastern side of the Philippines, the 18 June, 2008 (top) and the 17 December, 2008 (bottom). Numbers correspond to currents which are nammed in the text. To create such a map, choose DT Delayed-Time data - Global- (Maps of) Geostrophic Velocity Anomalies, Variable(s): Vector (U,V), the date, and a restricted geographical area (here, for a defined date, 2 maps had been created and then pasted together).

The western equatorial Pacific Ocean is an area with a complex circulation. This area plays an important role in the basin-scale circulation and in the development of El Niño events. Furthermore it's the place where waters flow westward, in the Indian Ocean, via the Indonesian seas.

The geostrophic velocities derived from SLA and plotted with vectors in the LAS can help to understand this circulation and its variations on a small area approaching the Philippines:

  • the North Equatorial Current (NEC, noted "1" on the opposite maps) flows westward and splits as it encounters the Philippines, separating into a northwestward-flowing current (the Kuroshio, noted "2") and the south-flowing Mindanao Current (noted "3"). The bifurcation of the NEC into these two branches moves in latitudes on the seasonnal timescale (the northernmost position occurs in October and the southernmost position in February) and on the interannual timescale (the bifurcation latitude takes place at higher latitudes during the El Niño years,
  • A quasi permanent Mindanao cyclonic eddy (noted "4")  corresponding to a depression is centered around 130°E and 7.5°N. It is associated with the turning of NEC waters at the eastern coast of the Philippines, and their subsequent flow to the east in the North Equatorial Countercurrent (noted "5").
  • An anticyclonic eddy is observed in June (map on top, (noted "6") northeast of Halmahera Island near 132°E and 3°N.

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