Accumulation and ablation on the Seward-Malaspina glacier system, Canada-Alaska

Abstract

Upper Seward Glacier, an intermontane ice body, is the principal source of nourishment for Malaspina Glacier, a piedmont sheet on the southern Alaska coastal plain. The state of health and degree of activity of this system, covering 1650 square miles and involving about 420 cubic miles of ice, are best evaluated through records of accumulation and wastage. Annual surplus in the accumulation area was 69 inches of water in budget year 1948–1949, 26 inches in 1947–1948, 17 inches in 1946–1947, and 30 inches in 1945–1946. A preliminary estimate for 1949–1950 is 30 inches, which is thought to be about normal under present conditions. Daily gross ablation of firn in mid-summer on upper Seward Glacier ranged from a mean of 0.30 inch of water to a maximum of 0.87 inch. Ablation on the upper Seward in the summer of 1948 was 75 per cent greater than in 1949 over a corresponding period of 32 days. Daily gross ablation on clean Malaspina ice averaged 2.32 inches of water in 1949 or nearly nine times the rate on upper Seward Glacier. As to material balance, 1948–1949 yielded a surplus of 9.01 × 10^(13) cubic inches of water owing to heavy accumulation and reduced ablation. Budget year 1947–1948 produced a deficit of 2.144 × 10^(14) cubic inches, more than counterbalancing the surplus of 1948–1949. Under existing climatological conditions even a normal year produces a deficit of about 2 × 10^(14) cubic inches. This glacier system is obviously in a poor state of health.

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