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Published December 1960 | Published
Journal Article Open

Oxygen-isotope ratios in the Blue Glacier, Olympic Mountains, Washington, U.S.A.


The mean per mil deviation from a standard (average ocean water) in the O^(18)/O^(16) ratio of 291 specimens of ice, firn, snow, and rain from the Blue Glacier is −12.4; extremes are −8.6 and −19.2. This is consistent with the moist temperate climatological environment. The O^(18)/O^(16) ratio of snow decreases with declining temperature of precipitation, and it also decreases with increasing altitude at 0.5/100 meters. Analyses of the three principal types of ice, coarse-bubbly, coarse-clear, and fine, composing lower Blue Glacier, show that ratios for coarse-clear ice are generally lower and for fine ice they are mostly higher than the ratios for coarse-bubbly ice. This indicates that the fine ice represents masses of firn and snow recently incorporated into the glacier by filling of crevasses or by infolding in areas of severe deformation. Coarse-clear ice masses may represent fragments of coarse-bubbly ice within a breccia formed in the icefall. Because of unfavorable orientation, these fragments could have undergone exceptional recrystallization with reduction in air bubbles and, possibly, a relative decrease in O^(18). A longitudinal septum in the lower Blue Glacier is characterized by higher than normal O^(18)/O^(16) ratios. These values are consistent with an origin for this feature involving incorporation of much surficial snow and firn near the base of the icefall. Samples from longitudinal profiles on the ice tongue suggest that ice close to the snout comes from high parts of the accumulation area. Analyses from the light and dark bands of ogives are compatible with the concept that the dark bands represent greatly modified insets of firn-ice breccia filling icefall crevasses. The range in ratios of materials is much greater in the accumulation area than in the ice tongue. This is attributed to homogenization, much of which takes place during the conversion of snow to glacier ice. This is supported by comparative analyses of snow layers when first deposited and months later, after alteration. Refreezing of rain and meltwater percolating into underlying cold snow is an important mechanism as shown by analyses of ice layers and lenses in the firn formed in this manner.

Additional Information

Copyright 1960 by the American Geophysical Union. (Manuscript received July 9, 1960.) The work of 1957 and 1958 on Blue Glacier was an International Geophysical Year activity under the auspices of the U.S. National Committee. The investigation was continued in 1959 with support from the National Science Foundation. The mass spectrometer used for oxygen-isotope analyses is the property of the Atomic Energy Commission. The National Park Service graciously granted permission to make the study and aided in many ways. Supplies and equipment were carried to the glacier by the U. S. Air Force and the U.S. Coast Guard. Equipment was loaned by the Snow, Ice and Permafrost Research Establishment of the U.S. Army Engineers and by the Office of Naval Research (contract N-1896-00). Personnel of the Snowdome project on upper Blue Glacier collected samples of snow during the winter of 1957-1958. Field colleagues C. R. Allen and J. C. Savage aided in the collection of other samples. William R. Fairchild of the Angeles Flying Service provided superb logistical support. John Nye, Henri Bader, and Edward Anders have kindly offered critical and much appreciated comments on the manuscript, but they do not necessarily endorse any statements made in this paper. Contribution No. 967, Division of Geological Sciences.

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