Surface Kuroshio Intrusion Evidenced by Satellite Geostrophic
Streamlines: Algorithm and Seasonal variations
Abstract
Using long-term satellite altimeter data, a new streamline-based
algorithm is developed to identify the Kuroshio intrusion types and
describe the seasonal variations of related dynamical properties.
Results from this new classification show that a mixing of leaping,
looping and leaking streamlines is the dominant form of Kuroshio
intrusion into the South China Sea (SCS). The leaping path is very
stable and crosses the Luzon Strait mainly through the Balintang Channel
regardless of seasons, while the streamlines leaking into the SCS is
more likely to intrude via the channel between the Babuyan Island and
the Camiguin Island. Large seasonal variations are found with the
percentage of each kind of streamline and the Luzon Strait Transport
(LST), but not with the intensity, width and current axis position of
the Kuroshio. The along-streamline analysis reveals that the seasonal
intrusion of the Kuroshio is essentially the seasonal variation of the
cyclonic shear part of the flow. A possible physical mechanism is
proposed to accommodate these seasonal characteristics based on globally
the vorticity (torque work) balance between the basin-wide wind stress
and the lateral friction, as well as locally the loss of balance between
the torques of interior stresses and normal stresses both provided by
the wall boundary, together with a plausible conjecture that the
seasonally-reversing monsoon can significantly modify the torque of the
interior stresses within the cyclonic shear part of the flow and thus
responsible for the seasonal variation of the Kuroshio intrusion.