Arctic river discharge trends since 7ka BP

a r t i c l e i n f o The Arctic hydrological cycle throughout the Holocene is analyzed based on the results of transient simulations with the coupled atmosphere-ocean circulation model ECHO-G. The results suggest a ~ 2% increase of mid-Holocene to preindustrial Arctic river discharges for the Eurasian continent. However, rivers of the North America Arctic realm show a moderate runoff decline of approximately 4 to 5% for the same period. The total river discharge into the Arctic Ocean has remained at an approximately constant preindustrial level since the mid-Holocene. The positive discharge trend within Eurasia is caused by a more rapid decrease in local net evaporation compared to a smaller decline in advected moisture and hence precipitation. This effect is neither recognized within the North American Arctic domain nor in the far eastern part of the Eurasian Arctic realm. A detailed comparison of these model findings with a variety of proxy studies is conducted. The collected proxy records show trends of continental surface temperatures and precipitation rates that are consistent with the simulations. A continuation of the transient Holocene runs for the 19th and 20th century with increased greenhouse gasses indicates an increase of the total river influx into the Arctic Ocean of up to 7.6%. The Eurasian river discharges increase by 7.5%, the North American discharges by up to 8.4%. The most rapid increases have been detected since the beginning of the 20th century. These results are corroborated by the observed rising of Arctic river discharges during the last century which is attributed to anthro-pogenic warming. The acceleration of the Arctic hydrological cycle in the 20th century is without precedence in the Holocene. High northern latitudes are known to play a prominent role in global climate changes. Minor variations of the overall climate system are presumed to cause accelerated nonlinear responses within the Arctic and Antarctic subsystems (Screen and Simmonds, 2010). In particular, atmospheric moisture transport from lower latitudes to the Arctic realm is predicted to increase substantially due to global warming (e. The Arctic Ocean contains only 1% of the global volume of sea water while receiving 11% of the world's annual river discharge (Shiklomanov et al., 2000). River discharges, as primary source in the Arctic freshwater budget (~3300 km 3 Even though the hydrological cycle of the Arctic is accelerating, river discharges do not show uniform trends. indicate a significant upward trend of …