Identifying Atmospheric Moisture Sources Contributing to Early or Late Melt Onset of Arctic Sea Ice

The timing of melt onset in the Arctic plays a key role in the evolution of sea ice throughout Spring, Summer and Autumn. Development of melt ponds increases the surface albedo allowing more energy to be absorbed from solar radiation. Early melt onset also allows for earlier development of open water between the ice floes, increasing solar absorption that warms the ocean mixed layer and enhances later and basal melt. Combined these processes enhance the ice-albedo feedback, resulting in more summer ice melt and delayed autumn freeze-up. A major catalyst of early melt onset is increased downwelling longwave radiation, which is amplified by increased levels of moisture in the atmosphere. Determining where this moisture originates from, and understanding the climate conditions that enable transport to the Arctic is therefore of keen interest. These questions are addressed through a back trajectory analysis using the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). Trajectories are created at locations with early, normal, and late melt onset to determine shifts in moisture source locations as the melt season progresses. These trajectories are then compared to climate patterns to find synoptic associations with moisture transport and melt onset. Results from this research advance our knowledge of Arctic climate in relation to melt onset and the timing and duration of ice-free conditions.