Recent current observations in the eastern Yellow Sea

Abstract

Observations of current velocity, pressure, and temperature in the eastern Yellow Sea from January 10 through April 12, 1986, together with geostrophic winds calculated from surface atmospheric pressure distributions, are analyzed for a study of the synoptic band response of the Yellow Sea to the wintertime winds. North wind pulses in the winter monsoon are found to give rise to northward flow bursts in the Yellow Sea trough, which appear to peak just as the wind relaxes and to be driven by a synoptic band north‐to‐south rise in bottom pressure, synchronous with the north‐wind pulses. The existence of a similar rise in coastal sea level indicates that the observed southward pressure rise is but an offshore extension of a setup along the west coast of South Korea forced by the north wind pulses. The advection, by northward flow bursts, of warm water from the south apparently causes the measured temperature to be substantially higher in the trough than in coastal waters at the same latitude and the observed rate of cooling in the trough to be less than half of that in coastal waters to the east. A winter‐to‐spring transition is also found in the bottom pressure records obtained in the trough, in which the mean north‐to‐south gradient in winter reverses suddenly in early March. A similar reversal also appears in sea level records along the west coast of South Korea. The reversal appears to be triggered by the weakening of the north winds at the arrival of spring.