Predicted changes in synoptic forcing of net precipitation in large Arctic river basins during the 21st century

Daily output from 15 global climate system models and 2 global reanalyses were analyzed to create a synoptic climatology of Arctic sea level pressure and to assess predicted changes in net precipitation over the Arctic. The method of self-organizing maps was used to create the synoptic climatology from 3 decades of model output: 1991 2000, 2046 - 2055, and 2091 - 2100. The model-derived synoptic climatology was compared to that from two reanalyses, for the period 1991 - 2000, and this comparison was used to select a subset of models that best reproduced the currently observed synoptic climate of the Arctic. Of the 15 models evaluated in this way, only 4 models were able to reproduce the key features of the Arctic synoptic climate as depicted by the two global reanalyses. The synoptic climatology created using the self-organizing map technique lends itself to the study of extreme events and the projections from this subset of 4 models indicate an increase in cyclonically dominated weather patterns over the 21st century. The models also projected an increase in net precipitation over the Arctic cap and the large Arctic river watersheds during the 21st century. Using the synoptic climatology, a method to assess thermodynamic- and circulation-related changes in net precipitation was derived. The results of this assessment indicate that thermodynamic changes are responsible for more than 75% of the predicted change in Arctic net precipitation during the 21st century.