Geophysical Research Letters

Long-term trend of Pacific South Equatorial Current bifurcation over 1950–2010

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Abstract

This study investigates the long-term change of the Pacific South Equatorial Current (SEC) bifurcation latitude (SBL) over 1950–2010 with Simple Ocean Data Assimilation version 2.2.4. Results indicate that the SBL averaged within upper 200 m has migrated southward at 0.020°S yr−1, comparable in magnitude with −0.024°N yr−1 for the North Equatorial Current bifurcation latitude (NBL). The SEC transport into the Coral Sea has increased. Due to the southward SBL migration, most of the increased SEC water was transported equatorward, contributing to the Equatorial Undercurrent intensification. Experiments with a nonlinear 1.5 layer reduced gravity model indicate that the southward migration of SBL is mainly caused by positive Ekman flux divergence trend in the eastern tropical South Pacific, while that of NBL is caused by negative Ekman flux divergence trend in the western tropical North Pacific.

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