IngentaConnect Post-depositional modification of stable water isotopes in winter...

Authors: Sinclair, K.E.; Marshall, S.J.

Source: Annals of Glaciology, Volume 49, Number 1, October 2008 , pp. 96-106(11)

Publisher: International Glaciological Society

Abstract:

To assess the seasonal stability of the δ¹⁸O stratigraphy in winter snowpacks in the Canadian Rocky Mountains, snow pits were sampled over three accumulation seasons at two field sites. These sites, Opabin and Haig Glaciers, are ∼160 km apart at similar elevations and represent windward and lee-slope environments respectively. At both sites, snow pits were sampled at one glacier and one forefield location throughout each accumulation season. Intra-seasonal changes in δ¹⁸O at each site were examined to determine the extent of post-depositional modification of isotope stratigraphies. At both glacier sites, there was minimal temporal change before the onset of spring melt in all years. In addition, the similar structure of δ¹⁸O profiles from both glacier sites suggests that regional controls govern the isotopic composition of solid-phase precipitation across the study area. At forefield locations, the absence of an insulating layer of ice at the base of the snowpack allowed for vapour transport and post-depositional modification of the seasonal δ¹⁸O signal. This did not result in consistent changes to the mean δ¹⁸O, deuterium excess and δD-δ¹⁸O regression line slopes in the lower layers of snow, and the observed smoothing of δ¹⁸O profiles was less than that simulated by applying a diffusion model to these snowpacks.

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Post-depositional modification of stable water isotopes in winter snowpacks in the Canadian Rocky Mountains