Recent Recession and Thinning of Okpilak Glacier, Northeastern Alaska

Compares Aug. 1958 photographs and observations of this valley glacier in the Romanzof Mts. with those of Leffingwell in 1907, cf. No. 9835. The indicated recession and thinning of the glacier in 51 years are confirmed by aerial photographs and topographic maps. The 1000 ± 100 ft, mean rate 20 ft/yr, probably increased in the 1950s. Thinning, estimated at 150 ft in the lower 1.2 miles of the glacier, occurred at about 3 ft/yr. The advance from which the ice is retreating is correlated with the Fan Mountain glaciation. Similar evidences of retreat and thinning are found in neighboring glaciers.