Wave-ice interaction strengthens eddy activity in Fram Strait

Abstract. A mesoscale eddy was detected by satellite in the MIZ of Fram Strait and verified by reference to the barotropic instability of the East Greenland Current (EGC). According to the reanalysis data, the eddy originated from a mother eddy that grew and diminished in a branch of EGC during the summer. After September 12, this branch of the EGC strengthened and became equally strong as the main body of the EGC by the end of September. As a result, the eddy grew into a strong mesoscale eddy, which was captured on October 4 by satellite. The strengthening of the branch may be attributed to the influence of wave-ice interactions. In September, sea ice expanded toward the open ocean as a result of the seasonal cycle and covered the branch of the EGC. Wave-ice interactions and eddy genesis were revealed by numerical simulations. When waves propagated into the ice zone, they dissipated quickly at the ice edge and produce an ice-edge jet, thus strengthening the background flow. The resulting enhanced barotropic instability helped small turbulence grow into large eddies. During the same period, an ocean front grew due to ice formation and dense water sinking, thus indicating that baroclinic instability may not play an important role in eddy genesis.