Future projections of cyclone activity in the Arctic for the 21st century from regional climate models (Arctic-CORDEX)

Changes in the characteristics of cycloneactivity (frequency, depth and size) in the Arcticare analyzed based on simulations with state-of-the-art regional climate models(RCMs) from the Arctic-CORDEX initiative and global climate models(GCMs) from CMIP5 under the Representative Concentration Pathway(RCP) 8.5 scenario. Most of RCMs show an increase of cyclonefrequency in winter (DJF) and a decrease in summer (JJA) to the end of the 21st century. However, in one half of the RCMs, cyclonesbecome weaker and substantially smaller in winter and deeper and larger in summer. RCMs as well as GCMs show an increase of cyclonefrequency overthe Baffin Bay, Barents Sea, north of Greenland, Canadian Archipelago, and a decrease overthe Nordic Seas, Kara and Beaufort Seas and overthe sub- arcticcontinental regions in winter. In summer, the models simulate an increase of cyclonefrequency overthe Central Arcticand Greenland Sea and a decrease overthe Norwegian and Kara Seas by the end of the 21st century. The decrease is also found overthe high-latitude continental areas, in particular, overeast Siberia and Alaska. The sensitivity of the RCMs' projections to the boundary conditions and model physics is estimated. In general, different lateral boundary conditions from the GCMs have larger effects on the simulated RCM projections than the differences in RCMs' setup and/or physics.