Satellite Observation on the Exceptional Intrusion of Cold Water in the Taiwan Strait

Abstract

We used satellite-derived sea surface temperature (SST) data for the winters of 1996 - 2008 to examine the exceptional intrusion of China Coastal Current into the Taiwan Strait. The long term observation reveals that, in 1999 and 2000, the strong wind (> 6 m s-1) lasted for 12 and 16 days with a drop of 5.35 and 5.5 degree in SST, respectively. The satellite data also showed that the China Coastal Current intruded from the north of the Chang-Yuen Ridge into the waters surrounding the Peng-Hu Islands, with wind speeds of more than 6.7 m s-1 lasted for 30 days during the same period. The exceptional intrusion resulted in the minimum SST of 12.6 degree on 16 February 2008, 7.8 degree lower than the 12-year average of February (20.4 degree). The higher SST (> 18 degree) appeared after 21 February 2008 indicating the north ward withdrawal of the cold water. During the period of 15 - 21 February 2008, the China Coastal Current intruded to as far south as the water around Peng-Hu Islands.

To compare the El Nino/La Nina events with regard to SST and wind speed, we found that SST was warmer in the El Nino winters (1998, 2003 - 2005) than in the La Nina winters (1999 - 2001, 2008), and wind speed was more intensive in the La Nina winters (1996, 1999 - 2001, 2006, 2008) than in the El Nino winters (1998, 2003 - 2005, 2007). In the winter of 2008, the wind speed sharply increased on 26 January and lasted for more than 30 days, with wind speed peaked at 7.36 m s-1. The monthly SST in February 2008 was about 7degree lower than that of the 12-year average. This decadal oscillation shows that the wind variation corresponds well with the El Nino/La Nina events, especially, the continuous strong wind in the La Nina winter of 2008. We thus suggest the influence of climate change on wind speed to be responsible for the change in the current. The exceptional cold SSTs around Chang-Yuen Ridge and Peng-Hu Is lands in February of 2008 probably were, there fore, caused by the more south ward intrusion of China Coastal Current driven by the continuous strong wind.

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