Variability and Trends in the Hydro-Climatology of the Major Eurasian Arctic Drainages

The hydro-climatology of the Arctic drainages plays an important role in the climate system by controlling freshwater discharge to the Arctic Ocean. However, information is limited regarding how the seasonal cycles of precipitation over the terrestrial watersheds are shaped by the relative roles of large scale vapor-flux convergence versus local/regional recycling of water vapor - at present, the relationships between precipitation (P) and evaporation (E) as they influence effective moisture (P-E) are not well understood. There is also a need to examine the hydrologic cycle in the context of the evidence for environmental change in northern high latitude lands during the past several decades. This includes increases in air temperature and reductions in snow cover, negative glacier mass balances, northward advances of the tree line, increased fire frequency and warming of soils and permafrost. There is also evidence that carbon accumulation in tundra regions has changed to a pattern of net loss. In recognition of these issues, a project has been initiated to assess the characteristics of and potential changes in the hydro-climatology of the major Eurasian Arctic drainages, focusing on the Ob, Lena and Yenesei basins. This approach is to combine gridded time series of precipitation, temperature, snow cover and snow depth based on station and satellite data with time series of vapor flux convergence, precipitation, precipitation minus evaporation and evaporation based on atmospheric reanalyses. Variability and trends in hydrologic budget components over the past several decades and their linkages with atmospheric circulation are discussed, and case studies are presented outlining atmospheric conditions associated with extreme monthly precipitation events on the basin scale during different seasons.