Recent Variations of Blue Glacier, Olympic Mountains, Washington, U.S.A.

Spicer, Richard

A compilation of terminus variation data from the early 19th century to 1987 is provided for Blue Glacier, the largest of 266 glaciers in the Olympic Mountains, Washington. Sources of the data include field studies of Neoglacial moraines and trimlines; written accounts and mountaineering photographs from 1890 to 1942; oblique and vertical aerial photography taken intermittently from 1955 to 1982, principally by Olympic National Park and the U.S. Geological Survey; two topographic maps (1935, 1956) of the Mount Olympus area and four glacier maps (1939, 1952, 1957, 1979); and nearly annual field measurement of the glacier terminus from 1938 to the present. By at least about 1890, Blue Glacier had retreated 535 m from early 19th-century Neoglacial-maximum moraines to the base of a spectacular 500-m icefall, where the forked ice front remained for the next three decades. Indian legend and scientific account alike attest to the crashing thunder caused by avalanching ice, until rapid retreat of more than 700 m from shortly before 1924 to 1953 witnessed withdrawal of the slender ice tongues from the valley and exposure of the underlying bedrock cliff. The principal terminus advanced slightly (2 m) in 1955, but retreated again by 1960 to its farthest up-valley position known. The first appreciable advance (164 m) since the early 19th century occurred from 1965 to 1980, most of which (122.9 m) was gained between 1971 and 1978. Nearly annual photographs from a station established in 1953 below the ice front provide sequential illustration of that change. Since 1980, the terminus has remained relatively stable. These variations occurred in broad synchrony with nearby glacier activity in the Washington Cascade Range and Olympic Mountains. Comparison of Blue Glacier variations with 5-yr moving averages of mean annual temperature, precipitation, and runoff for the Olympic Peninsula shows that rapid recession before 1953 coincided with a temperature maximum and precipitation minimum, and that temperature minima and precipitation maxima just preceded times of greatest glacier advance in 1955 and from 1971 to 1978.

Recent Variations of Blue Glacier, Olympic Mountains, Washington, U.S.A.

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