An Energy Balance Model of Potential Glacierization of Northern Canada

Abstract

The probable sites of Laurentide Ice Sheet inception and the amount of climatic change required are examined by means of a computer model of the energy balance of a snow cover. With various amounts of climatic change, the climatic snowline over northern Canada is computed, and its intersection with the land surface predicts the broad distribution of perennial snow cover. It is found that (1) as expected, Baffin Island is the most probable site of ice sheet initiation, but contrary to previous opinion, Keewatin is just as susceptible to glacierization as Labrador-Ungava; (2) much more climatic change is required for very extensive glacierization of either Keewatin or Labrador-Ungava than has been suggested, equivalent to a 10 to 12°C summer temperature decrease; (3) increased winter snow accumulation (the maximum observed at each station) does not greatly increase the area of perennial snow cover, nor does the possible effect of unrecovered glacioisostatic rebound; and (4) an estimate of the local climatic effects of a Northern Hemisphere summer insolation minimum (due to Earth-orbital variations) gives perennial snow cover on Baffin Island and the central Canadian Arctic west of Baffin Island.

The probability of ice sheet growth on Keewatin is supported by other evidence. A map of 30 June snow-cover probability based on satellite observations is produced; it shows that extensive summer snow cover is more likely on Keewatin than on Labrador-Ungava. Comparison of old glacial striae mapped in Keewatin with computed potential boundaries of perennial snow cover suggests that ice spread south from the central Canadian Arctic, including northern Keewatin, initiated with summer temperatures perhaps 8°C lower than at present.