Abstract/Summary

Recent reductions in sea ice extent have made the Arctic Ocean more accessible for industries including shipping, oil exploration and tourism. The Arctic has been increasingly used for shipping since 2012, and this trend will likely continue over the 21st century as sea ice extent reduces further. Thus, increasing the exposure to synoptic-scale Arctic storms, which cause hazardous weather. But Arctic storms are not fully understood. This thesis aims to further understand present-day Arctic storm statistics and development, and better evaluate changes in risk due to climate change. The representation of present-day Arctic storm statistics is found to be consistent across the ERA5, ERA-Interim, JRA-55, MERRA-2 and NCEP-CFSR reanalyses. Arctic storm statistics are found to be more sensitive to the storm tracking variable used. Approximately twice as many storms per season were identified in ERA-Interim in winter using 850 hPa relative vorticity, rather than mean sea level pressure. In most seasons the structure and development of Arctic storms is found to be similar to mid-latitude storms (and conceptual models e.g. Norwegian Cyclone Model). But the structure and development of Arctic summer storms is found to be different. The composite structure of Arctic summer storms shows that they typically undergo a structural transition around the time of maximum intensity, from having a baroclinic structure to an axi-symmetric cold-core structure throughout the troposphere. Arctic summer storms are also long-lived, potentially causing prolonged hazardous conditions. Future climate RCP8.5 HadGEM3-GA3.0 simulations (2086-2110) performed at horizontal resolutions of 150 km, 60 km, and 25 km from the UPSCALE project (Mizielinski et al., 2014) show that the Arctic environment will change due to climate change. Consequently, Arctic storm track density will likely decrease over Arctic Ocean in winter and increase around Greenland in summer. This response is consistent between all projections at each resolution, adding confidence in this response.