New papers:
Goal:
Quantify patterns of flow and fluxes, with a goal of establishing predictability.
Main Proposal 1.2MB PDF
Background:
The boundary currents off the east coast of the Philippines are of critical importance to the general circulation of the Pacific Ocean. The westward flowing North Equatorial Current (NEC) runs into the Philippine coast and bifurcates into the northward Kuroshio and the southward Mindanao Current (MC) (Figure 1; Nitani, 1972). The partitioning of the flow into the Kuroshio and MC is an important observable. Quantifying these flows and understanding bifurcation dynamics are essential to improving predictions of regional circulation, and to characterizing property transports that ultimately affect Pacific climate. Fluctuations in the Kuroshio and MC can significantly impact variability downstream. For example, the Kuroshio penetrates through Luzon Strait into the South China Sea and onto the East China Sea shelf. The Kuroshio front dramatically alters stratification and may impact internal wave climate. This study incorporates observation, theory, and modeling to make fundamental advances in our knowledge of the origins of theKuroshio and Mindanao current.
Figure 1. Region of study. The major currents of the region are identified: the North Equatorial Current (NEC), the Kuroshio, and the Mindanao Current (MC).
Drifter observations of currents at 15 m depth form a comprehensive dataset of direct observations. According to these observations (Figure 2), the roots of the Mindanao Current is located at approximately 11 degree north, 1.5 degree south of the latitude at which the mean NEC takes a southward and a northward bend (Centurioni et al., 2004) while approaching the Philippine Archipelago. The Kuroshio however, appears to become a stable, detectable boundary current (with speeds in excess of 0.8 m/s) between 16 degree north and 18 degree north. Although the drifter data are too sparse to allow a definitive picture of the annual cycle in the region, the available data suggest that the two-dimensional circulation pattern north of 11 degree north changes seasonally. A region of complex and highly variable near surface flow exists off the western (Philippines) boundary and north of the roots of the Mindanao Current, i.e. between 12 degree north and 16-18 degree north. Regions characterized by intermittently high speeds (Figure 2) extend eastward and away from the region’s western boundary from 18 degree north to 24 degree north and between 9 degree north and 12 degree north. Those are also the regions of relatively large, seasonally variable, Eddy Kinetic Energy (EKE), while lower EKE is generally found between those two latitude bands.
Figure 2. Tracks of drifters color-coded by instantaneous (6 hourly) speed.
