Variation in the Kuroshio intrusion: Modeling and interpretation of observations collected around the Luzon Strait from July 2009 to March 2011

Furthermore, the relative differences (Δmax (z)) in deeper layers exceed those of the surface layer. Circulation patterns in surface geostrophic currents and the Argo float trajectory confirmed the results of mooring station N2. The Kuroshio intrusion velocity variation modeled using the 1/12° global HYCOM model resembled the observation on both seasonal to interannual scales.

Modeled variation in the zonal mean velocity anomaly was also consistent with Niño3, Niño4, and North Equatorial Current (NEC) bifurcation latitude indices, indicating concurrent impacts of the ENSO influence. Monsoon winds strongly affect the seasonal variation while the weak upstream Kuroshio transport induced by El Niño, strongly affects the interannual variation, such as 2009–2010 winter. In 2010-2011 winter, the impact of winter monsoon forcing still exists in the LS.

However, the stronger upstream Kuroshio transport during this period did not allow the Kuroshio to penetrate into the LS deeply. This explains why the 2009-2010 winter Kuroshio intrusion (El Niño event) was stronger than that of the 2010-2011 winter (La Niña event).