The Arctic Water Cycle in ECHO-G scenarios


Within a warming climate the hydrological cycle is expected to intensify yielding to more precipitation over the Arctic [IPCC report [(Houghton et al., 2001]]. Changes in P-E (precipitation minus evaporation) over the Arctic and changes in river runoff discharge into the Arctic seas change the total freshwater flux into the Arctic Ocean and the northern North Atlantic and therefore affect the thermohaline circulation (THC). In most coupled climate model integrations the THC weakens as carbon dioxide increases [IPCC report [Houghton et al., 2001]]. Although under global warming conditions the P-E budget over the Arctic (north of 65°N) increases on a higher rate than the Arctic river runoff, Arctic river runoff still contributes 70 to 80 % of the total freshwater flux (P-E and runoff) into the Arctic [Wu et al., 2005]. Therefore the Arctic river runoff dominates the freshwater input into the polar oceans. Due to the large uncertainties in determining the P-E budget over the polar seas the Arctic river runoff may be a variable suitable for validating the freshwater input into the Arctic seas in model simulations. Another important role of the Arctic water cycle is played by the cryosphere. Under climate change scenarios the positive feedback effects of snow cover - and even more important - sea ice cover changes are key processes for the polar amplification of a global warming.
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