Numerical Study On The Circulation In The Yellow Sea In Winter

The wintertime circulation in the Yellow Sea is carefully investigated by a combination of remote sensing data, in situ observation data and numerical modeling. The results are as follows:(1)A winter onshore warm tongue extending from the Yellow Sea Warm Current to the south of Jiangsu coast and an offshore cold tongue extending form the north of Changjiang River(Yangtze River) estuary to the southwest of Jeju Island(South Korea) are newly identified, which seems to be inconsistent with the previously accepted view that in winter there existing a cross-shelf current from the Old Huanghe Delta to the southwest of Jeju Island. Further analysis shows that: the onshore warm tongue is driven by prevailing northerly wind in winter, the offshore cold tongue is induced by the tidal residual current from the north of Changjiang River estuary to the southwest of Jeju Island, and there is inexistence of the cross-shelf current from the Old Huanghe Detla to the southwest of Jeju Island in winter. The cold water and suspended sediments around the northern Jiangsu coast are carried to the north of Changjiang River estuary by the southward wind-driven coastal current and then transported to the southwest of Jeju Island by the tide-induced residual current, forming the offshore cold tongue and tubid plume. The research reveals not only the formation mechanisms of onshore warm tongue and offshore cold tongue, but also the pathway and dynamic mechanisms of the offshore transport of the suspended sediment.(2)The in situ observation data and model results indicate that there exists a bottom branch of the Yellow Sea Warm Current(YSWC) wandering northwestward at the bottom of Yellow Sea Trough in winter. Model results demonstrate that the bottom branch of the YSWC is driven by the northerly wind and the strength of the northerly wind determines the strength of the bottom branch of the YSWC. The bottom branch of the YSWC flows over several cavities on the seabed and the pathway is S-shaped and leaning to the west due to conservation of potential vorticity. Numerical experiments also reveal that the bottom friction has important influence on the twobranches of the YSWC. The bottom branch of the YSWC becomes rather weak when the bottom friction parameter is very little. With the increase of the bottom friction parameter, the west branch of YSWC becomes weaker while the bottom branch of YSWC becomes stronger.(3)The formation and evolution of the Qingdao Cold Water Mass are analyzed on the basis of the in situ observation data and ROMS model, the research reveals that the pathway of the Bohai Sea Coastal Current varies with the seasons which plays an import role in the formation and evolution of the Qingdao Cold Water Mass.