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Circulation in the Philippine Archipelago simulated by 1/12 and 1/25 global HYCOM and EAS NCOM
Harley E. Hurlburt, E. Joseph Metzger, Janet Sprintall, Shelley N. Riedlinger, Robert A. Arnone, Toshiaki Shinoda, and Xiaobiao Xu
Naval Research Laboratory
(Abstract received 12/29/2010 for session X)
ABSTRACT
In the Philippines Experiment (PhilEx) 1/12 and 1/25 global HYCOM and 1/12 EAS NCOM nested in global NCOM provided a global context for the Philippine Archipelago circulation. This archipelago provides two secondary routes for both the Indonesian throughflow and the western boundary current of the Pacific northern tropical gyre. The deeper route enters from the north via Mindoro Strait, after passing through Luzon Strait and the South China Sea. The second route enters directly from the Pacific via the shallow Surigao Strait. Both pathways exit via Sibutu Passage at the southern end of the Sulu Sea and both are deeper than the pathway into the Indonesian Archipelago via the Java Sea. The Sulu Sea outflow contributes to the flow through Makassar Strait, the primary conduit of the Indonesian throughflow, at all depths above the Sibutu Passage sill. In the model simulations 2004 and 2008, 2008 the central year for PhilEx observations, are extreme opposite anomalous years with strong southward Mindoro transport in 2004 and mean northward transport in 2008, but with little effect on the Surigao-Dipolog transport. The associated HYCOM sea surface height anomalies in the western tropical Pacific and the South China Sea during these extreme years were verified by satellite altimetry. A PhilEx mooring in Mindoro Strait and 1/12 global HYCOM were used to estimate mean transports of 0.24 Sv northward over the anomalous observational period and 0.95 Sv southward over 2004-2009. Only 1/25 global HYCOM simulated the observed four-layer flow in Dipolog Strait and the persistent cyclonic gyre in the western Bohol Sea, observed in all four PhilEx cruises and in ocean color imagery. A 1/12 global HYCOM simulation with tides generated the hydrostatic aspect of the internal tides within the Philippine Archipelago, including a strong internal tidal beam observed crossing the Sulu Sea, which was generated at Sibutu Passage.
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2011 LOM Workshop, Miami, Florida February 7 - 9, 2011