Abstract
The Arctic region is warming two to three times faster than the global mean, intensifying the hydrological cycle in the high north. Both enhanced regional evaporation and poleward moisture transport contribute to a 50–60% increase in Arctic precipitation over the 21st century. The additional precipitation is diagnosed to fall primarily as rain, but the physical and dynamical constraints governing the transition to a rain-dominated Arctic are unknown. Here we use actual precipitation, snowfall, rainfall output of 37 global climate models in standardised 21st-century simulations to demonstrate that, on average, the main contributor to additional Arctic (70–90°N) rainfall is local warming (~70%), whereas non-local (thermo)dynamical processes associated with precipitation changes contribute only 30%. Surprisingly, the effect of local warming peaks in the frigid high Arctic, where modest summer temperature changes exert a much larger effect on rainfall changes than strong wintertime warming. This counterintuitive seasonality exhibits steep geographical gradients, however, governed by non-linear changes in the temperature-dependent snowfall fraction, thereby obscuring regional-scale attribution of enhanced Arctic rainfall to climate warming. Detailed knowledge of the underlying causes behind Arctic snow/rainfall changes will contribute to more accurate assessments of the (possibly irreversible) impacts on hydrology/run-off, permafrost thawing, ecosystems, sea ice retreat, and glacier melt.
Highlights
The Arctic region is warming two to three times faster than the global mean, intensifying the hydrological cycle in the high north
Changes in total precipitation, which in turn can be attributed to atmospheric moisture transports converging over the Arctic[1,2,3], to sea-ice-retreat induced surface evaporation changes[4], and to microphysical processes that transform atmospheric moisture into clouds and precipitation[3]
Magnitude and duration of various impacts of Arctic precipitation trends depend crucially on whether the additional precipitation will fall as snow or rain[5], it is imperative to accurately determine the underlying causes behind the steep increase in projected Arctic rainfall, including its dependence on local warming
Summary
The Arctic region is warming two to three times faster than the global mean, intensifying the hydrological cycle in the high north. We use actual precipitation, snowfall, rainfall output of 37 global climate models in standardised 21st-century simulations to demonstrate that, on average, the main contributor to additional Arctic (70–90°N) rainfall is local warming (~70%), whereas non-local (thermo)dynamical processes associated with precipitation changes contribute only 30%. The effect of local warming peaks in the frigid high Arctic, where modest summer temperature changes exert a much larger effect on rainfall changes than strong wintertime warming This counterintuitive seasonality exhibits steep geographical gradients, governed by nonlinear changes in the temperature-dependent snowfall fraction, thereby obscuring regional-scale attribution of enhanced Arctic rainfall to climate warming. All precipitation starts as snow, especially in the polar regions, but thawing temperatures in atmospheric layers between the surface and the cloud base cause the snow to melt and transform into rain This melt process, which is essentially driven by local temperature trends, is the main contributor to the increase in Arctic rainfall (~70%). The combined models project that rainfall will become the dominant form of Arctic precipitation around the year 2080 (in the RCP8.5 scenario)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
