Natural Spatial and Temporal Variation in Hydrometeorology Over the Eurasian Arctic Drainage Basin in the 20th Century Based on Observational Records

Significant increases in the fresh water discharge to the Arctic Ocean from Eurasia with an average annual rate of 2.0+-0.7 km3/year have been found for the last 60 years by Peterson et. al.(2002). The reason for this increase, whether natural variability, global change or both, is unclear. But we do need to identify the primary sources of these changes. Using an update of the R-ArcticNET database (http://www.R-ArcticNET.sr.unh.edu) along with newly developed human impact data sets (irrigation lands, reservoirs, population and water use) we identify the long-term observational gauges with minimal upstream human influence. We use this gauge subset to identify seasonal and annual variations of the hydrometeorological elements (e.g. river runoff, precipitation, air temperature) for the natural watersheds. This regionalization of the Eurasian Arctic drainage allows us to map out the dominant causes of change and provide insight in the variability of the hydrological cycle. This preliminary analysis has shown three general tendencies in hydrometeorology change across the Eurasian Arctic Ocean drainage basin: 1) increases in annual runoff up to 25% due primarily to a rise in precipitation in European North and Western Siberia; 2) significant winter increases (5-50%) in runoff for all regions due to a shorter cold period (increasing air temperature) and rising ground water storage; 3) decrease in annual and especially spring runoff (10-30%) in the Southern regions of the Ob and Yenisey basins as a result of winter precipitation decline and earlier snow melt.