Wintertime Large Temperature Inversions in the Yellow Sea Associated With the Cheju and Yellow Sea Warm Currents

Large temperature inversions in the Yellow Sea during winter were investigated by analyzing conductivity-temperature-depth data collected in January and February 1986, April 1996, and February 1997. Large inversions with temperature differences across inversion layers greater than 2 degrees C were observed at three places: southwest of Korea, southeast of the Shantung Peninsula, and on the northeastern flank of the Changjiang Banks. Pronounced thermohaline fronts were commonly established where warm offshore waters with high salinity were found below cold coastal waters with low salinity. In the southwestern area of Korea, where the front develops in an east-to-west direction, the Cheju Warm Current water flows eastward to the south of the front, while north of the front, cold Korean coastal water flows westward. In the southeastern area of Shantung Peninsula, where the front forms in northeast to southwest, the Yellow Sea Warm Current flows northeastward on the offshore side, while cold Chinese coastal water flows southwestward. Moderate temperature inversions were observed midwest of Korea and on Changjiang Banks when warm offshore waters extended into cold coastal areas. In the inversion areas, warm waters are heavier than cold waters, reflecting a stronger contribution of salinity to density than that of temperature. Consequently, isotherms and isohalines in the inversion areas commonly decline downward toward cold water areas. We concluded that the occurrence of large inversions is closely related to the advection of the Cheju Warm Current and Yellow Sea Warm Current waters to the thermohaline frontal zones where the warm offshore waters underlay lighter cold coastal waters. Plain Language Summary Temperature inversion phenomenon plays an important role in understanding the mixing process and circulation in the ocean. Temperature usually decreases with increasing depth. However, this normal temperature profile is not always maintained. In the ocean, temperature inversion is defined as a specific temperature structure in which the temperature at deeper depths is higher than that at shallower depths. Recent studies reported occurrences of large temperature inversions in winter southwest of Korea. However, precise locations and detailed structures of significantly large temperature inversions in the cold season remain unclear for the Yellow Sea. Our results show occurrences of large inversions during winter at three places southwest of Korea, southeast of the Shantung Peninsula, and on the Changjiang Banks where cold coastal waters and warm offshore waters meet.