What Controls the Extreme Flow Through the Kerama Gap: A Global Hybrid Coordinate Ocean Model Reanalysis Point of View
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NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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The temporal variability of volume transport from the North Pacific Ocean to the East China Sea ECS through the Kerama Gap between Okinawa Island and Miyakojima Island-a part of Ryukyu Island Arc is investigated using a 20-year global HYbrid Coordinate Ocean Model reanalysis with the Navy Coupled Ocean Data Assimilation from 1993 to 2012. We study the causes of extreme flow events defined as the volume transport through the Kerama Gap exceeding one standard deviation 4.50 Sv above inflow, from the North Pacific into the ECS or below outflow, from the ECS to the North Pacific the mean volume transport 1.95 Sv. In our results, the impinging mesoscale eddies from the Pacific Ocean are the most important factor in controlling the extreme flow occurrence, explaining 70 68 of the mean extreme inflow outflow-mean volume transport anomaly. Extreme inflow outflow through the Kerama Gap is associated with the impinging anticyclonic cyclonic eddies along the eastern side of Okinawa andor cyclonic anticyclonic eddies to the southwest of the gap. The Kuroshio frontal meanders cause the mean Kuroshio axis to shift away from toward the Kerama Gap during the extreme inflow outflow-mean events and play a secondary role in determining the extreme flow occurrence, representing 15 14 of the mean extreme inflow outflow-mean volume transport anomaly. The interannual variability of the flow through the gap also plays a subsidiary role, explaining another 13 14 of the mean extreme inflow outflow-mean volume transport anomaly.
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