A Survey of the Atmospheric Physical and Dynamical Processes Key to the Onset of Arctic Sea Ice Melt in Spring

Yiyi Huang1, Xiquan Dong1*, Baike Xi1 and Yi Deng2

1Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA

2School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, GA, USA

September sea ice concentration (SIC) is found to be most sensitive to the early melt onset over the East Siberian Sea and Laptev Sea (73°-84°N, 90°-155°) in the Arctic, a region defined here as the area of focus (AOF). Then four early melting years and four late melting years were selected and compared over this area. In the early melting years, the positive Arctic Oscillation (AO) phase is dominant during springtime, which is coupled with a poleward shift of storm tracks, intensified storm activity in the AOF and consequently enhanced northward transport of moist and warm air.  As a result, positive anomalies of precipitable water vapor (PWV) and/or cloud fraction and cloud water path were found over the AOF, increasing downward longwave radiative flux at the surface. The associated warming effect further contributes to the initial melt of sea ice. In contrast, the late melt onset is linked to the negative AO phase in spring accompanied with negative anomalies of PWV and downward longwave flux at the surface. The increased downward shortwave radiation during middle to late June plays a more important role in triggering the melting, aided further by the stronger cloud warming effects than normal.