Linkages Between Tropopause Polar Vortices and the Great Arctic Cyclone of August 2012

Coherent vortices in the vicinity of the tropopause, referred to as tropopause polar vortices (TPVs), are common features in the Arctic. TPVs may interact with and strengthen jet streams, as well as act as precursor disturbances for the development of Arctic cyclones. Arctic cyclones may be associated with strong surface winds and poleward advection of warm, moist air, contributing to reductions in Arctic sea-ice extent. Also, heavy precipitation, strong surface winds, and large waves accompanying Arctic cyclones may pose hazards to ships moving through an increasingly ice free Arctic Ocean. The Great Arctic Cyclone of August 2012 (hereafter AC12) is an example of an intense Arctic cyclone. AC12 formed on 2 August 2012 over central Siberia and attained a minimum sea level pressure (SLP) of 964 hPa on 6 August 2012 over the Arctic in the ERA-Interim reanalysis dataset. Strong surface winds associated with AC12 led to reductions in Arctic sea-ice extent during a time in which sea ice was thin. TPVs are hypothesized to play a role in the life cycle of AC12. The purpose of this study is to investigate the linkages between TPVs and AC12.

The ERA5, a high-resolution reanalysis dataset with a horizontal resolution of 31 km, will be utilized to investigate the linkages between TPVs and AC12. Two TPVs, TPV 1 and TPV 2, likely play a role in the development of AC12. TPV 1 approaches AC12 in a region of strong baroclinicity, likely supporting the development of AC12 via baroclinic processes. TPV–jet interactions involving both TPV 1 and TPV 2 likely contribute to the formation of a dual-jet configuration and jet coupling over AC12. The presence of warm, moist air and relatively strong lower-tropospheric ascent in the region of jet coupling likely contributes to the formation of a potential vorticity (PV) tower associated with AC12. Interaction between TPV 1 and the PV tower likely supports the intensification of AC12. After attaining its minimum SLP, AC12 moves slowly over the Arctic, where its expansive surface wind field contributes to reductions in Arctic sea-ice extent. This study illustrates that TPVs may play important roles in the life cycles of Arctic cyclones, which may lead to reductions in Arctic sea-ice extent.