Identification of different types of Kuroshio intrusion into the South China Sea |
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Authors: | Feng Nan Huijie Xue Fei Chai Lei Shi Maochong Shi Peifang Guo |
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Institution: | (1) School of Marine Sciences, University of Maine, Orono, ME, USA;(2) College of Physical and Environmental Oceanography, Ocean University of China, Qingdao, China |
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Abstract: | Kuroshio intrusion into the South China Sea (SCS) has different forms. In this study, a Kuroshio SCS Index (KSI) is defined
using the integral of geostrophic vorticity from 118° to 121° E and from 19° to 23° N. Three typical paths (the looping path,
the leaking path, and the leaping path) were identified based on the KSI derived from the weekly satellite Absolute Dynamic
Topography from 1993 to 2008. The KSI has a near normal distribution. Using ±1 standard deviation (σ) as the thresholds, the leaking path is the most frequent form with the probability of occurrence at 68.2%, while the probabilities
of occurrence for the looping path and the leaping path are 16.4% and 15.4%, respectively. Similar analysis is also conducted
on the daily Hybrid Coordinate Ocean Model (HYCOM) Global Analysis from 2004 to 2008. The results are generally consistent
with the KSI analysis of the satellite data. The HYCOM data are further analyzed to illustrate patterns of inflows/outflows
and the maximum/minimum salinity as representatives of the subsurface/intermediate waters. The Kuroshio bending and the net
inflow through the Luzon Strait reduce from the looping path to the leaking path to the leaping path. However, the Kuroshio
subsurface water intrudes farthest into the SCS for the leaking path. Vorticity budget associated with the different intrusion
types is then analyzed. The tilting of the relative vorticity, the stretching of the absolute vorticity, and the advection
of planetary vorticity are important for the change of vorticity, whereas the baroclinic and frictional contributions are
three orders smaller. |
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