Response of evapotranspiration and water availability to the changing climate in Northern Eurasia

Northern Eurasian ecosystems play an important role in the global climate system. Northern Eurasia (NE) has experienced dramatic climate changes during the last half of the 20th century and to present. To date, how evapotranspiration (ET) and water availability (P-ET, P: precipitation) had changed in response to the climatic change in this region has not been well evaluated. This study uses an improved version of the Terrestrial Ecosystem Model (TEM) that explicitly considers ET from uplands, wetlands, water bodies and snow cover to examine temporal and spatial variations in ET, water availability and river discharge in NE for the period 1948-2009. The average ET over NE increased during the study period at a rate of 0.13 mm year(-1) year(-1). Over this time, water availability augmented in the western part of the region, but decreased in the eastern part. The consideration of snow sublimation substantially improved the ET estimates and highlighted the importance of snow in the hydrometeorology of NE. We also find that the modified TEM estimates of water availability in NE watersheds are in good agreement with corresponding measurements of historical river discharge before 1970. However, a systematic underestimation of river discharge occurs after 1970 indicates that other water sources or dynamics not considered by the model (e.g., melting glaciers, permafrost thawing and fires) may also be important for the hydrology of the region.