Dramatic weakening of the ear-shaped thermal front in the Yellow Sea during 1950s–1990s
The ear-shaped thermal front (ESTF), formed by the convergence of the Yellow Sea Warm Current (YSWC) and the Shandong Coastal Current (SCC), is a very important oceanic phenomenon in the Yellow Sea (YS) in winter. In situ measurements and reanalysis datasets all demonstrate that the ESTF has been weakening during 1950s–1990s, and a similar weakening trend is also found in winter monsoon over the YS. Numerical experiments show that the weakening of winter monsoon can induce an anomalous circulation in the YS on multi-decadal timescale with northward anomalous currents along China’s coast and southward anomalous currents in the central YS—generally opposite to seasonal mean circulation. The anomalous circulation causes slowdown of the YSWC and the SCC, and thus weakens the ESTF. Since the ESTF plays important roles in regional ocean dynamics and air-sea interactions, its weakening has important implications for regional climate in the YS in winter.
Key wordsthermal front Yellow Sea circulation monsoon multi-decadal variability
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NCEP reanalysis dataset is provided by the NOAA/OAR/ESRL PSD (http://www.esrl.noaa.gov/psd/); ERA-40 reanalysis dataset is prepared by the European Centre for Medium-range Weather Forecasts (http://apps.ecmwf.int/datasets/); in situ SST data are provided by the National Marine Data and Information Service, State Oceanic Administration, China; SODA reanalysis can be downloaded from http://soda.tamu.edu/data.htm; CORA reanalysis dataset is provided by the WMO-IOC Centre for Marine Meteorological and Oceanographic Climate Data (http://www.cmocchina.cn/web/guest/access-to-metadata). AVHRR Pathfinder Version 5.2 (PFV5.2) data are obtained from the US National Oceanographic Data Center and GHRSST (http://pathfinder. nodc.noaa.gov).
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