Investigating Recent Summer Arctic Cyclone Structure and Evolution

Abstract

Arctic cyclones (ACs) have large impacts on sea-ice redistribution and are hazardous to communities in the region, yet the structure and evolution of summer ACs is not fully understood. We aim to link mechanisms that strengthen ACs to their structure at the time of maximum Eady Growth Rate (maxEGR) and minimum sea level pressure (minSLP) for both cold-core and warm-core cyclones. Structure and evolution of summer ACs from 2013–2022 are investigated using an atmospheric GCM with winds and temperature constrained in varying vertical windows. We investigate the extent to which ACs can be controlled by nudging above the boundary layer, above 500 hPa, and above the tropopause (i.e., above 300 hPa). This strategy allows us to separate competing sources of baroclinicity from the surface and atmospheric boundary layer versus the free troposphere. Although deeper storms at minSLP are more likely to be cold core and cold-core storms are nearly always associated with tropopause polar vorticies (TPVs), we find that nudging above the mid troposphere is not enough to constrain the cyclone —- the entire free troposphere must be nudged to capture the full structure of a TPV and its association with an AC. In addition, warm versus cold core is a valid classification at both maxEGR and minSLP.