Variations Of Heat Flux And Heat Budget In The East China Sea

The East China Sea (ECS) is a marginal sea adjacent to a vast continental shelf towards the western Pacific. The Kuroshio which is the strong western boundary current of the Pacific Ocean flows along the continental slope and brings huge amount of heat from South to North. It is known has important influence on the thermal structure and circulation. Cold, fresh shelf water is distributed on the continental shelf, while warm saline Kuroshio water occupies the area around the shelf break and further offshore.The shelf break is a key region influencing the water properties on the shelf as there, important onshore cross-frontal transports of heat and freshwater from the Kuroshio take place.In order to study the heat flux at air-sea interface on seasonal and inter-annual time scales, we use a net surface heat flux (Qnet) product obtained from the Objectively Analyzed air-sea Fluxes (OAFlux) project and the International Satellite Cloud Climatology Project (ISCCP), to study the seasonal variations of air-sea heat fluxes in the Northwestern Pacific Marginal Seas (NPMS) and their role in sea surface temperature (SST) seasonality. The seasonal variations of Qnet which is generally determined by the seasonal cycle of LH are in response to the advection-induced changes of SST over Kuroshio and its Extension. The oceanic thermal advection which have a significant effect on the SST and hence the sea-air humidity plays a primary role and explains the maximum heat losing along the Kuroshio. The heat transported by the Kuroshio makes it have a longer period of heat losing over Kuroshio and its Extension. The positive anomaly of heat content corresponds with the maximum heat loss along the Kuroshio. The oceanic advection is inferred to control the variations of heat content and hence the surface heat flux. This study will help us to understand the mechanism controlling variations of the coupled ocean-atmosphere system in the NPMS.The latent heat flux(LH) from OAFlux dataset through 1958 to 2006 were used to investigate the long-term variations of LH in the East China Sea (ECS). The relationships between LH and the related physical variables in both ECS and the Pacific are examined. The study showed that there is a steady increase in the ESC averaged LH in the last 50 years, with the maximum increasing rate along the axis of the Kuroshio. By examining the wind stress curl variations in the Aleutian low area, it's indicated that the wind stress curl there is highly correlated with the sea-air humidity difference which dominants LH in the ECS. It might be the wind stress curl in the North Pacific not the local wind in the ECS dominants the variations of LH. The lead and lag correlation, related the sea-air humidity difference in the ECS and the wind stress curl in the Aleutian low area (30°N-60°N,160°E-140°W) indicates a 4-yr lag of LH in the ECS to the wind stress curl. This delay might because the adjustment of the gyre circulation to a change in the wind field.In order to understand the role of the Kuroshio in the East China Sea, we use a global ocean model with regionally focused high resolution (1/10°) in the East China Sea (ECS), to study the oceanic heat budget in the ECS. The time-averaged temperature flux across the Taiwan Strait (TWS), Tsushima Strait (TSS) and the 200m isobath between Taiwan and Japan are 0.20PW,0.21PW and 0.05PW, respectively. The residual heat flux of 0.04PW into the ECS is balanced by the surface heat loss. The eddy temperature flux across the 200m isobath is 0.005PW, which accounts for 11.2% of the total temperature flux. The Kuroshio onshore temperature flux has two major sources, the Kuroshio intrusion northeast of Taiwan and southwest of Kyushu. The Ekman temperature flux induced by the wind stress in the ECS shows the same seasonal cycle and amplitude with the onshore temperature flux with a maximum in autumn and a minimum in summer. We conclude that the Ekman temperature flux dominants the seasonal cycle of Kuroshio onshore flux. The inter-annual variability is dominated by the variations of sea surface height caused by the advection rather than the local atmospheric forcing.