Why is there upwelling off the northeastern coast of Taiwan when the wind is downwelling-favorable? 

Dr. Leo Oey (Princeton University)

Abstract
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Vertical motions in the ocean are intricately linked to the horizontal
movements of water, and affect the ocean's ecosystem.  For example,
upwelling brings cool and nutrient-rich water from the ocean's depths to the
surface, and promotes phytoplankton-bloom of importance to fishery.
According to the conventional theory, upwelling adjacent to a coast arises
because surface water is forced offshore by the wind and a compensating
cooler water is transported onshore up the sloping bottom of the continental
shelf.  In the East China Sea, this upwelling-favorable wind is from the
south.  Curiously, off the northeastern coast of Taiwan, observations often
indicate upwelling when the wind is from the north, i.e. is
downwelling-favorable.   We will explain that this phenomenon is caused by
the nonlinear response of the shelf waters to wind acting on the strong
horizontal shears of the Kuroshio.