High Resolution Estimates of Sea Ice Melt-Freeze Transitions in the Northern Canadian Arctic Archipelago from Radarsat

The northern Canadian Arctic Archipelago (CAA) historically contains high concentration of multi-year ice (MYI). Previous research has shown that this region receives a continuous supply of MYI from the Arctic Ocean that is subsequently flushed southward into the Western Perry Channel during the summer melt season. This amount has never been quantified and the controls on southward advection have only been crudely investigated using coarse spatial resolution passive microwave observations that do not provide sufficient information regarding dynamics and thermodynamics for the sea ice in the northern CAA. This paper evaluates the utility of high spatial resolution synthetic aperture radar (SAR) to better understand the controls on sea ice dynamics within the northern CAA. SAR data was acquired from RADARSAT-1 between April and October, 2005, with an average temporal resolution of 3 days and spatial resolution of 100 m. A melt-freeze transition algorithm was developed to estimate the melt onset date. This is based on the temporal evolution of the backscatter coefficient (σo), which can be thresholded into melt onset for both seasonal first year ice (FYI) and MYI. The amount of sea ice flowing through the northern CAA was determined using the Canadian Ice Service Automated Ice Tracking System. Results indicate that melt onset dates for FYI are observed approximately two weeks earlier than MYI. The earlier melt onset date for FYI resulted in an increased open water area within the CAA, which provided more leeway for southward flow of MYI from the Arctic Ocean, via the northern CAA; leading to earlier than expected MYI flushed into the Western Parry Channel.