An inventory of Norway's glaciers and ice-marginal lakes from 2018–19 Sentinel-2 data

Abstract

We used Sentinel-2 satellite imagery at 10 m resolution to map the extent of Norway's glaciers and ice-marginal lakes over 2018–19. We applied a standardized semi-automated band ratio method to derive glacier outlines and ice-marginal lakes. To optimise the results, we manually edited the ice-lake interfaces, debris, snow and parts of the glaciers situated under shadow. We compared our Sentinel-2 derived outlines with very high-resolution aerial orthophotos and Pléiades satellite orthoimages. Glaciers larger than 0.3 km2 have area differences within 7%, whereas values are larger for smaller glaciers. The orthophotos and orthoimages provide more details and a higher mapping accuracy for individual glaciers, but require manual digitisation, have smaller spatial and temporal coverage and can have adverse snow conditions. We found a total glacier area of 2328 ± 70 km2 of which the ten largest glaciers accounted for 52%. The glacier area decreased 15% since the previous inventory (Landsat data from 1999 to 2006), the reduction being largest in northern Norway (22%) compared to southern Norway (10%). We detected more than 2000 previously undetected smaller glaciers and ice patches (covering 37 km2) and 360 new ice-marginal lakes.