Interconnected hydroclimatic shifts in Northern Eurasia: decadal variability and the impact of Arctic change

Abstract The Arctic's rapid transformation due to climate change significantly impacts Northern Eurasia. Eastern Siberia experienced increased summer precipitation and permafrost thaw in the mid-2000s, leading to wetter surfaces and higher river runoff. Furthermore, Arctic warming is linked to winter cooling in Eurasia, indicating a major disruption in the interconnected Arctic Ocean–atmosphere–vegetation–permafrost–river system. Research on these changes in Northern Eurasia focuses on the water cycle, particularly summer rainfall and winter snowfall, which are crucial for water resources and climate feedback. Japanese research institutions have played a vital role since the 1990s, collaborating with Russian and Mongolian counterparts through projects, integrating field observations, remote sensing, and modeling. Understanding changes in Eurasian precipitation and atmospheric water vapor transport is crucial for assessing the impacts of Arctic climate change, particularly considering westerly, poleward, and southward transport. Summer precipitation is influenced by the recirculation of water vapor resulting from repeated cycles of precipitation and evapotranspiration over land areas, and potentially "Siberian Atmospheric Rivers." Decadal atmospheric circulation shifts, possibly amplified by warming, have contributed to events like the East Siberian wet period. In winter, Arctic warming paradoxically links to both less snow cover and extreme cold snaps with heavy snowfall in Eurasia due to increased evaporation from reduced Arctic sea ice along the Eurasian side. The "Warm Arctic, Cold Eurasia" (WACE) pattern is debated, with models suggesting that it may be part of a larger atmospheric variability. Eastern Siberian boreal forests, adapted to permafrost, utilize both rainwater and meltwater within the soil active layer. The wet period of 2004–2010 significantly altered surface water dynamics, initially increasing evapotranspiration but eventually causing waterlogging and shifts in vegetation and permafrost near the surface. Major Siberian rivers significantly contribute to the Arctic Ocean's freshwater inflow. Satellite data revealed an increase in terrestrial water storage in the Lena River basin during the wet period. These changes, along with permafrost dynamics, directly influence river runoff, with the wet conditions leading to summer flood peaks. Future research should consider multi-scale interactions, long-term climate change, and feedback processes to understand these complex and interconnected environmental changes in Northern Eurasia.