Winter upwelling off Luzon in the northeastern South China Sea

Abstract

A major upwelling region centered about 100 km offshore between 16° and 19°N off northwest Luzon in the South China Sea is revealed in the distributions of temperature, salinity, and dissolved oxygen concentration during a cruise in December 1990. Upward movement of water low in dissolved oxygen can be identified to a depth of 300 m. Climatological distributions of temperature and upper ocean heat content and tracer distribution obtained from a recent numerical experiment lend support to the existence of this upwelling region. Results from a general circulation model of the South China Sea further show that upwelling off Luzon occurs between October and January, in agreement with the climatological data. Current structures obtained from a simple two‐layer model and the general circulation model both suggest that this upwelling is not driven by local winds but contains a large, remotely forced component arising from the basin circulation. The upwelling is sustained by offshore Ekman drift from above and a converging northward undercurrent from below. The would‐be downwind coastal jet in the surface layer is largely offset by currents associated with the winter circulation gyre. Upwelled water with high nutrient content spreads southwestward in January and could be an important nutrient source for the surface water in the interior South China Sea in spring.

Seasonal Variability of Carbon Chemistry at the SEATS Site, Northern South China Sea Between 2002 and 2003

“…2. They are consistent with the general features reported previously for South China Sea waters (Gong et al 1992;Chen and Huang 1996;Shaw et al 1996;Lin et al 1999;Chen et al 2001;Wong et al 2002), and have been used frequently to distinguish them from other water masses (e.g., the Western Philippine Sea water) upon mixing. As shown in …”

Seasonal variability of surface phytoplankton in the Northern South China Sea: A one-dimensional coupled physical-biogeochemical modeling study

“…Obviously, the study area is away from the previously reported coastal upwelling regions in the SCS (Shaw et al, 1996;Jing et al, 2009;Gan et al, 2009) but partly includes the South East Asia Time-Series Station (SEATS station, Wong et al, 2007). The bottom topography is relatively uniform with domain averaged depth >3500 m.…”

“…Tang et al (1999) and Wang et al (2010) investigated the winter phytoplankton bloom phenomena occurred off the southwest of Luzon Strait in winter using both satellite derived data and shipboard measurements. They suggested that the phytoplankton bloom was mainly attributed to the winter upwelling occurring there (Shaw and Chao, 1994;Shaw et al, 1996). Using a three dimensional coupled physical-biogeochemical model, Liu et al (2002Liu et al ( , 2007 examined the spatial and temporal distributions of chlorophyll-a and primary production under the influence of monsoon winds in the SCS.…”

Winter phytoplankton bloom induced by subsurface upwelling and mixed layer entrainment southwest of Luzon Strait

“…As such, the upwelling is difficult to detect from satellite-derived sea surface temperature (SST) images (Udarbe-Walker and Villanoy, 2001). Shaw et al (1996) initially reported this winter upwelling, pointing out that the upwelling in this area was affected by a remotely forced component arising from the basin-wide gyre circulation. However, Shaw's results were based on only one cruise in December, 1990.…”