Abstract
AbstractAtmospheric humidity, clouds, precipitation, and evapotranspiration are essential components of the Arctic climate system. During recent decades, specific humidity and precipitation have generally increased in the Arctic, but changes in evapotranspiration are poorly known. Trends in clouds vary depending on the region and season. Climate model experiments suggest that increases in precipitation are related to global warming. In turn, feedbacks associated with the increase in atmospheric moisture and decrease in sea ice and snow cover have contributed to the Arctic amplification of global warming. Climate models have captured the overall wetting trend but have limited success in reproducing regional details. For the rest of the 21st century, climate models project strong warming and increasing precipitation, but different models yield different results for changes in cloud cover. The model differences are largest in months of minimum sea ice cover. Evapotranspiration is projected to increase in winter but in summer to decrease over the oceans and increase over land. Increasing net precipitation increases river discharge to the Arctic Ocean. Over sea ice in summer, projected increase in rain and decrease in snowfall decrease the surface albedo and, hence, further amplify snow/ice surface melt. With reducing sea ice, wind forcing on the Arctic Ocean increases with impacts on ocean currents and freshwater transport out of the Arctic. Improvements in observations, process understanding, and modeling capabilities are needed to better quantify the atmospheric role in the Arctic water cycle and its changes.
Highlights
The atmosphere contains water in the forms of vapor, liquid, and ice
Feedbacks associated with the increase in atmospheric moisture and decrease in sea ice and snow cover have contributed to the Arctic amplification of global warming
As mild winters in high latitudes are associated with increased atmospheric moisture, a positive relationship has been generally identified between the total cloud cover, Arctic Oscillation index, and a poleward shift of synoptic-scale storm tracks [Eastman and Warren, 2010; Serreze et al, 1993; Zhang et al, 2004]
Summary
The atmosphere contains water in the forms of vapor, liquid, and ice. The total water content in the atmosphere is approximately 13,000 km3 [Gleick, 1996], of which 200 km over the Arctic [Serreze et al, 2006]. The study was more focused on the ocean than atmosphere, the results for the latter included important estimates for the mean values, annual cycles, and interannual variations for the total (i.e., vertically integrated) water vapor (TWV), evapotranspiration (i.e., the sum of evaporation from the Earth surface and transpiration from plants), precipitation, and net precipitation (i.e., precipitation minus evapotranspiration) over the Arctic sea and land areas (Figure 1). This paper is a contribution to the “Arctic Freshwater Synthesis (AFS)” We point out the different definitions, when the differences affect the conclusions made
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