Unprecedented coastal upwelling in the East/Japan Sea and linkage to long-term large-scale variations

摘要

Unprecedented cold water was observed off the east coast of Korea in the summer of 2007, with the lowest temperature since 1961. The 9-year QuikSCAT satellite scatterometer wind field showed that the spectacular coastal upwelling was induced by Ekman transport to the offshore area by strong southerly winds. These characteristic winds were produced by the large scale air pressure distribution of typhoon Pabuk to the west, which stayed longest for the past half century, along with the North Pacific High (NPH) in the east. The duration of both tropical depressions and the westward moving NPH have shown characteristic increasing trends over several decades, which facilitate favorable conditions for the surface cooling. The negative trend in coastal water temperatures, in contrast with a positive trend offshore by global warming, supports the conclusion that small scale sea surface temperature variations at the coastal area could be remotely affected by long-term large-scale variations.