Elevation changes of ice caps in the Canadian Arctic Archipelago

Abstract

[1] Precise repeat airborne laser surveys were conducted over the major ice caps in the Canadian Arctic Archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region. Our measurements reveal thinning at lower elevations (below 1600 m) on most of the ice caps and glaciers but either very little change or thickening at higher elevations in the ice cap accumulation zones. Recent increases in precipitation in the area can account for the slight thickening where it was observed but not for the thinning at lower elevations. For the northern ice caps on the Queen Elizabeth Islands, thinning was generally <0.5 m yr À1 , which is consistent with what would be expected from the warm temperature anomalies in the region for the 5 year period between surveys, and appears to be a continuation of a trend that began in the mid-1980s. Farther south, however, on the Barnes and Penny ice caps on Baffin Island, this thinning was much more pronounced at over 1 m yr À1 in the lower elevations. Here temperature anomalies were very small, and the thinning at low elevations far exceeds any associated enhanced ablation. The observations on Barnes, and perhaps Penny, are consistent with the idea that the observed thinning is part of a much longer term deglaciation, as has been previously suggested for Barnes ice cap. On the basis of the regional relationships between elevation and elevation change in our data, the 1995-2000 mass balance for the archipelago is estimated to be À25 km 3 yr À1 of ice, which corresponds to a sea level increase of 0.064 mm yr À1 . This places it among the more significant sources of eustatic sea level rise, though not as substantial as the Greenland ice sheet, Alaskan glaciers, or the Patagonian ice fields.

Summer melt rates on Penny Ice Cap, Baffin Island: Past and recent trends and implications for regional climate

“…Over the period 1979-2010, the linear trend in precipitation was in fact negative (À0.62 mm a À1 ; Table 1). If precipitation did recently increase in the southern Baffin Island region as suggested by Abdalati et al [2004], and if this resulted in higher net ice accumulation on Penny Ice Cap, then the summer melt rates for the corresponding period may be underestimated by the measured MF percentages.…”

“…As equation (1) shows, however, MF % are not determined solely by temperature (melt), but also by the ice accumulation rate. Using selected records from Baffin Island weather stations, Abdalati et al [2004] inferred a slight increase (15%) in precipitation for the Baffin Island region during the 1990s, but regionally-averaged precipitation anomalies for the eastern Arctic ( Figure 2d) show little evidence of this. Over the period 1979-2010, the linear trend in precipitation was in fact negative (À0.62 mm a À1 ; Table 1).…”

“…Surface ablation near the glacier margin (<600 m) was $2.5 m of ice equivalent in 2007-08, but exceeded 3 m of ice equivalent in 2010-11. From airborne laser altimetry surveys, Abdalati et al [2004] estimated mean thinning rates (=net surface lowering) of 0.2-0.5 m a À1 on the western margin of Penny Ice Cap between 1995 and 2000. Elsewhere on the ice cap margin, thinning rates exceeded 0.4 m a À1 over the same period.…”

“…Thus Weber and Andrieux [1970] give a revised altitude of 1838 m for site A1, initially reported at 2050 m [Orvig, 1954]. Airborne laser altimetry surveys conducted over Penny Ice Cap since 1995 [Abdalati et al, 2004] [Jacobs et al, 1972;Weaver, 1975;Mokievsky-Zubok et al, 1985]. [Ward, 1954], 1979 [Holdsworth, 1984], 1995(R. Koerner, unpublished data, 1995 and 2010-11 (this work).…”

Accelerating thinning of Kenai Peninsula glaciers, Alaska

“…More recently studies have begun to explore the potential to observe glacial changes through active remote sensing methods. This has involved airborne profiles using laser altimetry to measure elevation changes [Arendt et al, 2002;Abdalati et al, 2004], and observing glacier surface elevations using the NASA/JPL spaceborne platform, Shuttle Radar Topography Mission (SRTM) [Muskett et al, 2003;Rignot et al, 2003]. By using remote sensing, it is possible to observe large and inaccessible glaciated regions thereby gaining a better understanding of mountain glacier changes and contribution to sea level rise.…”