Sir, Glacier advances apparent and real
I would like to comment on Dr. R. Streiff-Becker’s conclusions regarding the advance of the Nisqually Glacier in your journal, Vol. 3, No. 22, 1957, p. 151.
First he draws attention to a small nunatak—it is perhaps one-third of a mile (0.5 km.) from Camp Muir in what is generally termed the Muir snowfield or glacier—indicating that there is an increased exposure of this mass, as shown by a comparison of photographs 1951 and 1955. This is quite apparent; however, it also may be shown, with equal justification, in comparing 1953 to 1955, that there has been an increase in snow cover for this latter period.
To belabor this is fruitless, however, unless the precise time and conditions of photography are known. Even a week may produce quite striking changes in the appearance of snow fields. There is a seasonal pack of as much as 27 feet (8 m.) of dense snow, of unusually high moisture content, at Paradise (elev. approx. 5500 ft., 1700 m.). This melts entirely during the summer so that the extent of firn can easily be miscalculated depending upon the date of observations. Snow pack is probably much greater on Mt. Rainier to at least 8000 and perhaps to to,000 ft. (2440–3050 m.) in elevation. The nunatak is approximately at 9000 ft. (2740 m.).
Furthermore, snow falls throughout the year at Mt. Rainier; I have seen the ground covered with new snow in August at the 5500 ft. elevation. Last year in August I was in the vicinity of the nunatak under discussion during a storm that left a foot (o.3 m.) of hard packed snow over that area. This snow persisted for a number of days on the rocks and longer over the old snow.
I believe therefore that there is a need for exercising caution in drawing conclusions from undated photographs. Although I agree with Dr. Harrison as to overall advance, his use of undated photographs is open to question: it may have caused Dr. Streiff-Becker and others, to reach erroneous conclusions.
Personal observations, made over the past four summers as a ranger-naturalist at Mt. Rainier National Park, lead me to differ with Dr. Streiff-Becker when he states that firn field levels are falling everywhere. Many trails, formerly snow-free early in the season, are now blocked by snow fields at least four years and probably older in age. I have found that the Paradise Glacier (to the east of the Nisqually) has made a very substantial growth in thickness since its low of some years ago. A pictorial record shows a high nunatak being overwhelmed by an ice cliff perhaps 75 ft. (23 m.) high.
I would criticize Dr. Harrison on a point which Dr. Streiff-Becker did not mention. He has indicated (p. 681, Vol. 2, No. 19 of the Journal) that there was an “estimated lag of fifty years in the germination of coniferous trees at a definite trimline at the position of a very poorly defined moraine”. This estimation does not agree with the findings of other investigators. Studies currently in progress, as on the Kautz (Mt. Rainier) where there is an adjacent source of seed, show lags of but a few years. In Alaska, D. B. Lawrence (Glacier fluctuations for six centuries in southeastern Alaska and its relation to solar activity, Geographical Review, Vol. 40, 1950, p. 202) found that “analysis of our ring counts from the stem bases of the sapling spruces revealed that the usual interval between the melting away of the ice and successful germination was three to five years on the ridge tops”. This follows the general conclusion reached earlier by William S. Cooper in his work with vegetation in the Prince William Sound Region, Alaska (Ecol. Monographs, Vol. 12, 1942, p. 1–22): Lawrence said that a tree seedling at timberline might take a half-century after recession of the ice (Transactions, American Geographical Union, Vol. 31, No. 2, Ap. 1950, ref. on page 244). As the Nisqually terminus is now at or near the 4500 foot (1370 m.) level and timberline some 2000 ft. (600 m.) higher this estimate of lapse time does not fit the circumstances discussed by Harrison.
Having regularly conducted groups during the past four summers to see the Nisqually Glacier, I have an intense interest in its response to the increased snowfall and cool, wet summers of the past years. I anticipate making a detailed study of fluctuations in snow pack adjacent to the Nisqually as indicated by tree growth, this summer.
Clark I. Cross,
Associate Professor Department of Geography
University of Florida, Gainesville 31 January 1958
