Abstract

The distribution pattern of stable-isotope ratio δ18O in cold glaciers, ice streams, and ice sheets has the potential to reveal past changes in flow rate, for example those associated with surges. In this study, we use a time-dependent numerical model of ice flow to establish that each surge creates a stratigraphic horizon across which δ18O is discontinuous. Two plausible relations between glacier geometry and δ18O in snowfall allow us to bracket the expected magnitude of this isotopic signal. These stratigraphic markers could be located by δ18O analysis of a longitudinal series of ice cores or by detailed longitudinal sampling of exposed ice.Calculations for a model with characteristics resembling those of Steele Glacier, Yukon Territory, showed that at most three stratigraphic markers could be detected at any one time. The discontinuities in δ18O were as large as 0.8‰. This is an order of magnitude larger than mass spectrometer precision but comparable to observed background noise at Steele Glacier.

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