The Canadian Arctic Archipelago (CAA) comprises multiple small glaciers and ice caps mostly concentrated on Ellesmere and Baffin Islands in the northern (NCAA) and southern parts (SCAA) of the archipelago, respectively. Because these glaciers are small and show complex geometries, current regional climate models, using 5 to 20 km horizontal resolution, do not properly resolve surface mass balance (SMB) patterns. Here, we present a 58-year (1958-2015) reconstruction of daily SMB of the CAA, statistically downscaled to 1 km from the output of the regional climate model RACMO2.3 at 11 km. By correcting for biases in elevation and ice albedo, the downscaling method significantly improves runoff estimates over narrow outlet glaciers and isolated ice fields. Since the last two decades, NCAA and SCAA glaciers have experienced warmer conditions (+1.1°C) resulting in continued mass loss of 28.2 ± 11.5 Gt yr-1 and 22.0 ± 4.5 Gt yr-1 respectively, more than doubling (11.9 Gt yr-1) and doubling (11.9 Gt yr-1) the pre-1996 average. While the interior of NCAA ice caps can still buffer most of the additional melt, the lack of a perennial firn area over low-lying SCAA glaciers caused uninterrupted mass loss since the 1980s. In the absence of significant refreezing capacity, this indicates inevitable disappearance of these highly sensitive glaciers.

Surface mass balance (SMB) components (mm w.e. per year), i.e. SMB, total precipitation (snow + rain), runoff and total melt (ice + snow), statistically downscaled from the output of RACMO2.3 to 1 km resolution covering the northern (NCAA) and southern (SCAA) Canadian Arctic Archipelago, averaged for the periods 1958-1995 and 1996-2015.

Supplement to: Noël, Brice P Y; van de Berg, Willem Jan; Lhermitte, Stef; Wouters, Bert; Schaffer, Nicole; van den Broeke, Michiel R (2018): Six decades of glacial mass loss in the Canadian Arctic Archipelago. Journal of Geophysical Research-Earth Surface, 123(6), 1430-1449