Landfast sea ice extent and variability in the Alaskan Arctic derived from SAR imagery

Landfast sea ice is a seasonal phenomena in the Alaskan Arctic and throughout its annual existence, between formation in late fall and break-up in late spring, it is shaped by a range of thermodynamic and dynamic forces. The results of a manual and an automated technique to derive positions of the seaward landfast ice edge (SLIE) as it changes over time from synthetic aperture radar (SAR) data covering the Alaskan Arctic coast and nearshore waters from east of Point Lay, Alaska to the Mackenzie delta. Observing the variability in the position of the SLIE for a large study area over the course of the year identifies the occurrences of significant change including the timing of freeze-up and break-up and episodic events in between. It is also possible to identify the maximum stable extent of the landfast ice for a given period, which should prove valuable for all nearshore activity in the Arctic. We can give a greater understanding of the factors controlling the SLIE position by calculating the standard deviation in landfast ice width along the coast. This analysis identifies stable nodes along the SLIE where variability is small and processes, as of yet unidentified, helps to stabilize the landfast ice edge