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Ocean eddies, fronts, and air-sea exchanges: Observations and high resolution simulations
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Northwestern Pacific Variability and its Connectivity to the South China Sea (Invited)
Wednesday 9th @ 1330-1350, Conference Room 4
Bo Qiu* , Department of Oceanography
University of Hawaii at Manoa
Presenter Email: bo@soest.hawaii.edu |
Oceanic circulation variability in the open Northwestern Pacific ocean is subject to strong wind stress curl forcing connected to the Pacific decadal oscillations (PDOs). Specifically, for the westward-flowing North Equatorial Current (NEC), a positive (negative) phased PDO forcing generates Ekman flux divergence (convergence) in the western tropical Pacific Ocean of 8-18N and works to lower (increase) the regional sea level and shift the NEC's bifurcation northward (southward) along the Philippine coast northward. Upon impinging the Philippine coast, these sea level anomalies circulate clockwise and permeate into the South China Sea (SCS) as coastal trapped waves via the Celebes and Sulu Seas. The coastal wave guide acts as a low-pass filter, allowing interannual and longer-frequency open Pacific Ocean sea level anomalies to enter the eastern SCS.
A positive (negative) phased PDO forcing also generates Ekman flux convergence (divergence) in the western subtropical Pacific Ocean of 18-30N. This convergence sharpens the eastward shear of the Subtropical countercurrent (STCC) and leads to enhanced generation of mesoscale eddies along the STCC band. Upon reaching the coast of the Luzon Island, these mesoscale eddies modulate the transport of the northward-flowing Kuroshio. When cyclonic mesoscale eddies impinging on the Kuroshio, they tend to reduce the Kuroshio transport and
cause it to take a looping path to intrude into the Luzon Strait. Such mesoscale eddy mediated intrusions contribute to the intra-seasonal watermass and sea level exchanges between the western Pacific and the SCS. |
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