Quasigeostrophic Dynamics of the Arctic Coastal Jet in Summer

The purpose of this paper is to contribute to the growing understanding of the characteristics of cyclones that form over, or move across the Arctic Ocean during the summer months (JJA). Arctic cyclones have become identified as regularly occurring phenomena, thereby motivating numerous studies of cyclone climatology along with some individual case studies. In particular, Arctic cyclone activity has been linked to the land-sea temperature contrast that forms along the Arctic coast during summer and its associated high latitude jet over northern Siberia and Alaska. We investigate individual cyclone behaviors via diagnostic analysis of quasigeostrophic (QG) vertical motions acting both across and along frontal zones (transverse and shearwise, respectively). The analysis reveals that while Arctic cyclones share familiar synoptic processes with mid-latitude cyclones, they manifest as more complex interactions among multiple systems at varying stages of development. Specifically, synoptic factors that can control the precise location and intensity of the baroclinic zone and its associated jet include the proximity of developing cyclones to the Arctic cold pool, forcing of QG vertical motion in multiple locations near the perimeter of cold core systems, and the constructive frontogenetic forcing by opposing temperature advection from two cyclones. While the high-latitude jet appears prominently in the summer climatology, we reveal that its tenuous but frequent presence is dependent on complex interactions among multiple, rapidly evolving cyclones.