Monitoring surface water content and biogeochemical responses in the area surrounding river mouths using multi-source satellite remote sensing

Rivers contribute to carrying biogeochemical constituents from terrestrial to marine biospheres. Land-margin ecosystems in rivers are critical ecosystems that provide an interaction between land and ocean. The ecosystems have experienced increasing climate and environmental changes in recent years. The variations of the surface water at the river mouth areas are closely linked with the changes in biogeochemical cycles, including greenhouse gas emission. Multi-source environmental remote sensing data records were utilized to analyze the relationship between surface open water fraction (Fw) and various environmental and biogeochemical parameters, such as precipitation, surface soil moisture, root-zone soil moisture, heterotrophic respiration, and CH4. The study focused on 253 river mouth locations, which were determined using the MERIT-Hydro map. The long-term (2002-2021) Fw data shows a strong, negative trend in the mean annual summer (Jun - Aug) Fw in northern low latitudes (<45 degrees N), there is a positive trend in northern high latitude (> 45 degrees N). The results show that 46% of the river mouths has a decreasing Fw trend, implying drier surface moisture conditions. The correlation results show the stronger correspondence between Fw and carbon variables at the river mouth.