Feedbacks between sea ice, surface cyclones, and tropopause-based vortices over the Arctic

Sea ice in the Arctic is declining with an accelerating pace, and six of the lowest sea ice extents during the satellite era have occurred since 2007. It is becoming increasingly evident that reductions in sea ice could impact the jet stream and global storm tracks, particularly during the autumn and early winter months, when large areas of newly open water increase the potential for upward heat and moisture transfer into the atmosphere. However, the physical mechanisms leading from these changes in the surface energy balance to changes in synoptic-scale events are unclear. One key factor that has not been previously considered is the role of tropopause polar vortices (TPVs). TPVs are important precursors to surface cyclogenesis, and their intensity is best maintained over high-latitude land or ice surfaces where radiative processes dominate over latent heating processes.

Here, we will examine the atmospheric response to sea ice loss from the perspective of TPVs under the hypothesis that TPV characteristics will change as a result of changes in the tropospheric heat and moisture budgets. This hypothesis will be explored using a series of carefully designed idealized and regional downscaling numerical modeling simulations. Results show that when in isolation, the unique mechanisms that enable TPVs to maintain intensity are eliminated over open water. Projections from a long-term high-resolution regional downscaling experiment show that instead of exhibiting net weakening, vortex amplitude is maintained while the preferred TPV locations shift in response to the additional heat and moisture over the ice-free Arctic Ocean. Changes in the composite structure of TPVs will be discussed, with an emphasis on the dynamical and physical feedbacks between TPVs, sea ice, and surface-based cyclones.