Upper-ocean temperature trends in the Eastern China Seas during 1976–1996

Temperature in the Eastern China Seas(ECS), including the Bohai, Yellow, and East China seas, is crucially important with regard to weather forecasting and fishery activities of adjacent countries. Although sea surface temperature(SST) in the ECS has demonstrated a dramatically accelerated trend of warming after a regime shift(1976–1996), trends beneath the surface remain poorly understood because of the sparsity of observations. This study used in situ hydrographic data from 1976 to 1996 to examine upperocean temperature trends in the ECS. It was found that the multilevel trends show consistency with that of the surface water; i.e., warming is faster in winter than summer. However, the magnitudes of the trends weaken with increasing depth. Furthermore, the seasonal dif ference in the upper ocean is mainly associated with the warm currents in the ECS, which implies an essential contribution from horizontal advection. These phenomena could also be detected from data acquired from the routinely observed PN and 34°N sections. The spatiotemporal patterns of temperature trends in the upper ECS extend our understanding beyond the SST, especially highlighting the role of ocean dynamics in forming temperature patterns beneath the surface in comparison with atmospheric ef fects.