Extreme climate events, such as heatwaves and intense rainfall are increasingly impacting watersheds and altering how carbon is transported from land to ocean. Understanding these changes is especially important in data-scarce regions like Asia.

We examined 20 years of satellite-based monthly data on total organic carbon (TOC) and the ratio of dissolved to particulate organic carbon (DOC:POC) across six major Asian river basins: temperate (Yangtze, Yellow), monsoonal (Ganges-Brahmaputra, Mekong), and tropical rainforest (Barito, Rikomanggar). These data were paired with temperature- and precipitation-based climate extreme indices. We applied Random Forest Regression to determine which climate extremes most strongly influence carbon variability.

In temperate basins, TOC increased with warmer minimum daytime temperatures and heavy rainfall. In monsoonal regions, warmer nights and moderate rainfall enhanced TOC, but extreme rainfall led to dilution and carbon loss. In tropical rainforest basins, TOC responded most strongly to river discharge and persistent wet conditions, indicating tighter hydrologic control. Notably, DOC:POC ratios were only predictable in tropical regions.

These findings reveal distinct climate-carbon relationships across climatic zones, providing new insights into which river basins are most vulnerable to specific extreme events.