Little Ice Age Permanent Snowcover in the Eastern Canadian Arctic: Extent Mapped from Landsat-1 Satellite Imagery

Abstract

Extensive areas of the eastern Canadian Arctic are light grey/white on both conventional black and white air photography and on multi-spectral LANDSAT-1 satellite imagery. These areas stand out in marked contrast to the darker toned surrounding terrain. Field investigations indicate that the light grey areas possess few lichens or plants; in contrast, their margins abut terrain with a mature lichen cover. Areas within the lichen trimlines are interpretcd as the sites of former permanent snowbeds and snowfields. Radiometric and lichenometric dates indicate that the episode of permanent snowfields occurred about 500 to 300 years ago with retreat starting between 300 and 70 years ago. The LANDSAT-1 satellite imagery at a scale of 1: 1000000 has proven ideal for mapping the regional extent of this former snow-cover and this is illustraled by two frames from north-central Baffin Island. Interpretation problems can arise from a number of sources, such as: light early summer or fall snowcover, limestene bedrock, recent outwash plains, and low clouds. However, ambiguities can be eliminated by inspection of LANDSAT-1 frames from different passes, by the examination of 1: 60 000 air photographs, by the use of 1: 250 000 scale contour maps, and by comparison with maps of the bedrock geology.

A comparison of Little Ice Age glaciation levels with those based on the present distribution of permanent ice/snow bodies indicates that during the Little Ice Age the regional snowline fell between 100 and 400 m: thus extensive areas of the upland plateaus of Baffin Island above 600 m were mantled by a thin but extensive permanent snowcover. This study serves to provide a realistic modet for the inception of a North American ice sheet.