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Seminar report. North Equatorial Current (NEC) bifurcation. 報告人：沈茂霖 (Mao-Lin Shen) 2014/9/15. Thermohaline Circulation. The Great Indo-Pacific Communicator. Fig. The Great Indo-Pacific Communicator. (by Oppo and Rosenthal, 2010, Science). NECt-Mindanao Current-Kuroshio (NMK) system.
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Seminar report North Equatorial Current (NEC) bifurcation 報告人：沈茂霖 (Mao-Lin Shen) 2014/9/15
The Great Indo-Pacific Communicator Fig. The Great Indo-Pacific Communicator. (byOppo and Rosenthal, 2010, Science)
NECt-Mindanao Current-Kuroshio (NMK) system Fig. Schematic chart of geostrophic volume transport relative to 1200 dbar-depth in the North Equatorial Current-Mindanao Current-Kuroshio (NMK) system. (by Nitani, 1972)
Cruise measure Fig. NEC bifurcation near the Philippine Coast. NEC flow poleward of this latitude turned north as the Kuroshio while flow to the south fed the Mindanao Current. (by Toole et al., 1990, JPO)
Cruise measure (a) 20 Sep 1987 (b) 23 April 1988 Fig. NEC bifurcation near the Philippine Coast in different cruise measures.
Fig. Time series of the NEC bifurcation latitude anomalies (solid line) versus the southern oscillation index (SOI) (dashed line). A 12-month running mean filter was applied. (by Qiu and Lukas, 1996, JGR)
NEC bifurcation point moves southward in summer and northward in winter. • The bifurcation is depth dependent. • The northernmost Bifurcation point is at warm ENSO phase (El Niño) and the southernmost at cold ENSO phase (La Niña). • The seasonal bifurcation and inter-annual bifurcation are due to different mechanisms.
Streamfunction (a) Summer (b) Winter Fig. Comparison different methods applied for determining streamfunction.
Summer and winter (1) (a) Summer (b) Winter Fig. Comparison of stream function on summer and winter.
Summer and winter (2) (a) Summer (b) Winter Fig. Comparison of stream function on summer and winter.
Depth dependence (a) 0-800 m averaged. (b) 0-400 m averaged. Fig. Stream function comparison of the flow rate integrated from different depths.
Depth dependence (a) 0-400 m averaged. (b) 400-800 m averaged. Fig. Stream function comparison of the flow rate integrated from different depths. An interesting phenomenon is the deep circulation in the SCS is stronger than surface circulation.
Annual variation of LST Fig. Annual variation of Luzon Strait Throughflow.
Impact of different sill depth (a) Realistic Bathymetry (b) Shallower Bathymetry Fig. Comparison of different sill depth.
Impact of different sill depth (a) Realistic Bathymetry (b) Shallower Bathymetry Fig. Comparison of different sill depth.
Impact of different sill depth Fig. Comparison of different sill depth. Top panel: RB; bottom panel: SB.
The impact of southern throughflow (a) 0 Sv (b) 8 Sv Fig. Comparison of stream function on different southern throughflow.
The bifurcation may be due to upstream flow rate and the local topography as well as the surrounding current system. • Depth dependent bifurcation may have seasonal variation and the mechanism shall be found. • Does the bifurcation have connection with the SSHa attributed by ENSO events?? How could we verify this by our model?? • The seasonal bifurcation is determined by the LST.
