2020 Dickinson Sydkap Hackweek: Ice loss in Southwestern Ellesmere and Northwestern Devon Islands since 1959, Nunavut, Canada

Abstract:

The Canadian Arctic Archipelago (CAA) is second only to Greenland in terms of ice volume, but local patterns of glacier area changes there are still poorly understood. To quantify rates of ice loss, we examined archived aerial photography (1959), and Landsat (1-8; 1970s to present day) and Sentinel-2 (2013 to present day) satellite scenes on the southwestern part Ellesmere Island, including Sydkap Ice Cap, North Kent Island, and the northwestern peninsula of Devon Island (Colin Archer Peninsula). We used QGIS to composite appropriate bands to make true-color scenes, and Landsat 7 and 8 scenes were pan-sharpened using the 15 m panchromatic band before manually digitizing ice boundaries. For larger glaciers with complex boundaries, NDSI values were used to generate initial boundaries that were later manually verified and/or corrected.

There were 182 separate ice bodies in 1974, and 190 in 2019; the increase in number is due to the segmentation of 38 of the original ice bodies into multiple smaller ones over the intervening 45 years. Sixty-two of the smaller ice bodies found in 1974 had been completely lost by 2019, some originally as large as 6.4 km². Preliminary results show that from 1974 to 2019 total ice area decreased by 18% (from 4942 to 4066 km² +/- 176.7 km²) with more than half of that occurring since 2000. Sydkap Ice Cap, which contains about 55 percent of the total ice area , lost about 5.8% of its area. There was a strong inverse relationship between percent area loss and initial ice area, with the average area of glaciers that lost 100% of their area since 1974 being 0.73 km². Our findings concur with previous studies which show that smallest ice bodies are most likely to disappear, and if melting rates continue at the average rate for 1974-2019, another 156 ice bodies with 2019 areas of less than 5 km² may be gone by the 2050s. While nearly all glaciers have retreated since 1974, a total of 12 advanced or remained at the same terminus position, which do not appear to be surge type. Of these, 11 are outlet glaciers to the Sydkap Ice Cap, and for the 6 with clear advances the termini in 2019 are from 150 to 400 m in front of the 1974 termini. This work provides an improved inventory of CAA glacier coverage and estimates of areal loss, from which we can gain a better understanding of how ice in the CAA is responding to climate change.