Runoff from Eurasian and North American rivers represents a significant source of freshwater to the Arctic Ocean. The variations of runoff influence the formation of the Arctic Ocean halocline through controlling the freshwater input to the Arctic Ocean. The changes of runoff also affect sea ice thermodynamics and thermohaline circulation. Moreover, the freshwater output from the Arctic Ocean, in the form of sea ice and reduced salinity seawater, has potential influence on the overturning cell of the global ocean through controlling the intensity of convection in the North Atlantic. Therefore, the freshwater balance in the Arctic Ocean plays important roles in global climate and water cycle. In this project, we will collect quality-controlled information of Arctic runoff observations and analyze seasonal-to-interannual variability of the Arctic runoff. Meanwhile, we will develop and improve a sea ice-ocean coupled model suitable for this project based on our long-term research on sea ice model. Combining the observational Arctic runoff analysis and sea ice-ocean coupled model, we will implement a series of model experiments, and explore the impacts of Arctic runoffs on the upper Arctic ocean structure, flux exchanges between sea ice and ocean, sea ice distributions, and the North Atlantic Deep Water formation, and associated possible mechanisms.