Characteristics and change of the Milne Ice Shelf, Nunavut, Canada, over the last 50 yrs

Canada has lost over 90% of its ice shelf area over the last century, including a loss of 214 km2 in summer 2008 alone. This study reports on volume and area changes for the 205 km2 Milne Ice Shelf between 1950 and 2009. We use ground penetrating radar profiles collected in spring 2008 and 2009 to produce the first ice thickness DEM for the Milne Ice Shelf. Maximum ice thicknesses reach ~100 m, with an average of 50-60 m, which helps to determine the range of ice thicknesses expected for ice islands which have recently calved from northern Ellesmere Island. Direct-line comparison of current ice shelf thickness to thicknesses obtained from a 1981 airborne radio echo sounding survey reveals thinning of ~5 m since 1981. Ice shelf surface area, determined from air photo mosaics (1950, 1959, 1974, 1984) and satellite imagery (ERS-1, ASTER, RADARSAT-1, RADARSAT-2), has decreased by ~28% since 1950. This has largely occurred from the conversion of ice shelf to epishelf lake ice at the rear of the Milne Ice Shelf, although some losses have also occurred from calving at the ice shelf front. This study also reports on variations in ice type across the Milne Ice Shelf determined from a combination of patterns of internal and basal properties and reflection characteristics derived from GPR data, shallow ice cores, and RADARSAT-2 imagery. These indicate that patterns of surface melting, snow accumulation and wind distribution gives rise to different ice types across the ice shelf. The front is largely composed of a thick layer of iced firn, the depth of which decreases with distance from the coast. Glacier and lake ice dominate the central and rear portions of the ice shelf.