Coastal upwelling in the East China Sea in winter

Abstract

[1] The dynamic mechanisms of the upwelling off the East China Sea (ECS) coast in wintertime are studied. First, the upwelling signals off the ECS coast are identified by the observed temperature, salinity, nutrients, and dissolved oxygen data obtained during the cruises in January 1999. The MASNUM wave-tide-circulation coupled model is then employed to simulate the hydrography of the ECS. Comparisons between the simulations and observations show that the model performance is satisfactory. On the basis of successful simulation, four numerical experiments are conducted to investigate the upwelling mechanisms. The results suggest that the density (or salinity) front, which separates the inshore Low Salinity Coastal Water and the offshore Taiwan Warm Current (TWC), is the primary inducement for the upwelling. Owing to strong density gradient, the baroclinic pressure gradient force (PGF) is quite large near the frontal zone, and this PGF elicits an upwelling branch along the topography slope. Wind, TWC, and tide affect the density front in extension and intensity, thus exerting subsidiary influences on the upwelling. According to Ekman's theory, the northerly monsoon is downwelling favorable. However, the net effects of wind on the upwelling off the ECS coast in winter are positive because it drives the Changjiang River Diluted Water (CDW) flowing southward and forms the density front. Similarly, the resultant effects of TWC on the upwelling are negative for obstructing the pathway of CDW. Tide contributes to the upwelling because tidal mixing facilitates the expansion of CDW.

Distribution and cross-front transport of suspended particulate matter over the inner shelf of the East China Sea

“…1) are controlled by the southward Zhe-Min Coastal Current (ZMCC) and the northward Taiwan Warm Current (TWC), which result in a front characterized by opposite currents and distinct temperature and salinity on the two sides. Moreover, the movement of the northward TWC is accompanied by its significant climbing tendency toward the shore (Su, 2005;Lü et al, 2006;Qiao et al, 2006;Xu et al, 2012). Ocean color and sea surface temperature (SST) data based on the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra satellite illustrate the obvious cross-shelf currents in the surface layer of the YS and the ECS in winter (Yuan et al, 2008;Yuan and Hsueh, 2010).…”

Upwelling induced by the frictional stress curl and vertical squeezing of the vortex tube over a submerged valley in the East China Sea

“…Furthermore, Qiao et al . [] and Lü et al . [] pointed out that a baroclinic PGF in a tidally generated density front induced the upslope current.…”

Numerical study on the origins and the forcing mechanism of the phosphate in upwelling areas off the coast of Zhejiang province, China in summer

“…The Taiwan Warm Current (TWC) is from (Guan and Fang, 2006). The shaded area indicates the study area where algal bloom and hypoxia as well as upwelling frequently occur (Hu, 1984;Li et al, 2002;Lv et al, 2007;Qiao et al, 2006;Wang and Wu, 2009;Zhu et al, 2011). The thin line represents the isobaths of 50 m, 100 m, 200 m, and 500 m, respectively.…”

“…1) has been increasingly noted for the frequently reported algal bloom events in its surface water (Chen et al, 2004;Wang and Wu, 2009) and the hypoxia in its bottom water (Chen et al, 2007;Li et al, 2002;Wei et al, 2007;Zhu et al, 2011). In addition, the upwelling in this area is very strong (Hu, 1984(Hu, , 1994Lv et al, 2006;Qiao et al, 2006;Wang and Wang, 2007a), and the famous Zhoushan fishing ground also lies in this area. The high fishery production in this area is likely induced by the high primary production in the water since the ecosystem is powered by primary production (Gong et al, 2003).…”