Glaciers of Yosemite National Park. Since 1931, C. A. Harwell. Yosemite Park naturalist, has made yearly observations and measurements of the glaciers of Mts. Lyell, Maclure, Dana, and Conness. The reports of this systematic study are of great value and set a high standard for others to follow.
A warm and prolonged melting period in 1933 greatly reduced all the glaciers of this district. Observations made in 1932 and 1933 at the various measuring stations show that during that year the termini retreated as follows: Lyell Glacier (east lobe), 18 ft., (west lobe), 7 ft. and 8 ft.; Maclure Glacier, 22 ft.; Dana Glacier, 67 ft. and 30 ft.; and Conness Glacier (east lobe), about 177 ft. The east lobe of Conness Glacier is reported to be very thin and so much reduced since 1932 that “a few light winters or heavy melting summers may cause this lobe to disappear entirely.”
On Lyell Glacier was found a dead mountain sheep which had been imprisoned in the ice. At this point the rate of flow of the ice was found to be about one-fourth inch per day, at which rate it would have required about 240 years for the carcass to be transported from the cliffs at the head of the glacier.
Correlating the observations of the glaciers over a period of three years with the data available on the meteorological conditions during that time has (quoting from Harwell’s report) demonstrated that summer melting and evaporating conditions are as important as the quantity of snow falling during the winter in determining advance or retreat of glacier fronts. It is as proper to speak of ‘heavy’ summers as it is to consider ‘heavy’ winters.”