Oceanic Upwelling Dynamics in East Asian Seas

Oceanic upwelling in the East Asian marginal seas arises primarily from wind-driven processes that bring cold, nutrient-rich deep waters to the surface along continental margins. Seasonal monsoon winds, especially the strong northeast winter monsoon and southwest summer monsoon, interact with coastline orientation, shelf bathymetry and current systems to establish persistent upwelling zones in the South China Sea, East China Sea and Taiwan Strait. These upwelling systems regulate primary productivity by replenishing nutrients such as nitrate, phosphate and silicate in the euphotic zone, thereby supporting prolific fisheries and influencing regional carbon cycling. The intensity and spatial distribution of upwelling exhibit both seasonal and interannual variability, modulated by large-scale climate modes including the Oceanic Niño Index and the East Asian monsoon index. Topographic features such as island chains and shelf breaks further shape the location and strength of upwelling cells, while tidal mixing and stratification govern short-term oscillations. An integrated understanding of these dynamics is essential for predicting ecosystem responses to climate change, managing fishery resources and assessing carbon sequestration in one of the world’s most productive coastal regions.

Research from Nature Portfolio

Recent studies have highlighted the pivotal role of the Taiwan Strait in mitigating phosphate limitation in the East China Sea. Observations spanning two decades reveal a significant increase in phosphate flux through the strait, surpassing inputs from major rivers and alleviating nutrient constraints on phytoplankton growth. This enhanced supply of phosphorus correlates with rising chlorophyll-a concentrations on the adjacent shelf, underscoring the strait’s function as a key conduit of essential nutrients.

Investigations of the quasi-cul-de-sac circulation in the Taiwan Strait during the northeast monsoon have demonstrated how the mixing of fresh, nutrient-rich coastal current water with saltier oceanic waters fosters optimal biological uptake. This mixing produces intermediate salinity and nutrient conditions that amplify chlorophyll-a concentrations and primary productivity in both the northern South China Sea and southern East China Sea, revealing a mechanistic link between monsoon-driven circulation and seasonal blooms.

Oceanic Upwelling Dynamics in East Asian Seas publication trend

The graph below shows the total number of articles in oceanic upwelling dynamics in east asian seas across all publications each year (not limited to Nature Index journals).

Technical terms

Upwelling: The upward movement of deep, cold, nutrient-rich water to the ocean surface.

Ekman transport: The wind-driven net water movement at right angles to the wind direction, caused by the Coriolis effect.

Stratification: The layering of water masses with different densities due to variations in temperature and salinity.

Thermocline: A subsurface layer characterised by a rapid change in temperature with depth.

Chlorophyll-a: The primary photosynthetic pigment in phytoplankton, used as an indicator of biomass.

References

1. East China Sea increasingly gains limiting nutrient P from South China Sea. Scientific Reports (2019).
2. Elevated primary productivity triggered by mixing in the quasi-cul-de-sac Taiwan Strait during the NE monsoon. Scientific Reports (2020).
3. Interannual Variations in the Summer Coastal Upwelling in the Northeastern South China Sea. Remote Sensing (2024).
4. Surface Upwelling off the Zhoushan Islands, East China Sea, from Himawari-8 AHI Data. Remote Sensing (2022).