What caused South China Sea throughflow to slow?

Coral records point to a long-term decline

Proxy records extracted from corals show a sustained, century‑long slowdown of the South China Sea Throughflow, the ocean corridor that moves heat and freshwater between the South China Sea and adjacent ocean regions. Those coral archives preserve chemical and physical signals that scientists use to reconstruct past ocean currents; the latest analyses indicate a clear, long‑term weakening consistent with warming trends.

Scientists link the decline to changes in the climate system driven by rising global temperatures. As the surface ocean warms, wind patterns, sea‑level gradients and density contrasts that drive regional circulation can shift, reducing the pressure gradients that power the throughflow. A weaker throughflow means less transport of warm water and freshwater out of the South China Sea, which can alter regional sea surface temperatures, salinity, and the timing and strength of monsoon and rainfall patterns.

Potential consequences

• Regional climate impacts, including shifts to local weather and rainfall regimes that affect agriculture and water supplies.
• Changes to marine ecosystems where species distributions and nutrient supply depend on currents.
• Impacts on heat redistribution that can feed back into larger ocean‑atmosphere dynamics.

While corals provide a valuable century‑scale record, the mechanisms linking global warming to the flow’s change remain an active area of research. It’s still unclear exactly how the throughflow will behave under future warming scenarios, but the proxy evidence signals an important regional response to a warming world.