Every year during late spring and summer

a patch of surface cold water exists near the eastern side of the Subei shoal patch. The main cause of the cold water is the monthly southward migration and climbing up of the deep cold water from the western part of the southern Huanghai Sea. The existence of the deep ditches on the north side of the underwater delta off Subei controls the position of this cold water. Another patch of cold water is commonly observed southwest of Jizhou Island on the surface in the region 32oN and 124o–124.5oE during late spring and summer. Based on analysis

this water comes mainly from the deep layers of the northwest area; its upwelling is related to the northward “impulsive” extension of the Taiwan Warm Current in the previous period

and its position is probably related to the underwater reef chain there.