Stable-Isotope (18O/16O) Tracing of Fresh, Brackish, and Sea Ice in Multi-Year Land-Fast Sea Ice, Ellesmere Island, Canada
Authors: Jeffries, Martin O.; Krouse, H. Roy; Sackinger, William M.; Serson, Harold V.
Source: Journal of Glaciology, Number 119, 1989 , pp. 9-16(8)
Publisher: International Glaciological Society
Abstract:Ice salinity and 18O/16O ratios were measured on 12 ice cores drilled from thick, multi-year land-fast sea ice (MLSI) off the north coast of Ellesmere Island, Canada. Fresh, brackish, and sea ice were identified in the ice cores using the 18O/16O ratios. Two cases are considered: case I, which assumes that no isotopic fractionation occurs on freezing; and, case 2, which assumes that a maximum isotopic fractionation factor (a) of 1.003 applies. The amount of each ice type is variable among the cores, but overall the 12 cores comprise 29.6% brackish ice, 70.0% sea ice, and 0.4% fresh ice in case I, and 42.3% brackish ice, 57.3% sea ice, and 0.4% fresh ice in case 2. The data suggest that time-dependent brackish sea-water stratification below the ice is Quite common and is often associated with the inverted bottom topography. However, the stratification is not always confined to small, areally limited under-ice melt pools in inverted depressions, and neither is it a summer-only phenomenon. Brackish ice growth apparently occurs in a brackish water layer that in some instances underlies the ice sheet year-round. For both case I and case 2 the salinity distribution in brackish ice is positively skewed, with 50% of salinity values occurring in the range 0−0.49%. Sea-ice salinity values are more evenly distributed. In case I, brackish ice has mean salinity and mean δ18O values of 0.66 and −19.9%, respectively, compared to mean values of 1.88 and −6.5%0 for the sea ice. In case 2, brackish ice has mean salinity and mean δ18O values of 0.75 and −18.1% compared to mean values of 2.03 and −5.2% for the sea ice. The salinity of brackish ice and sea ice, ice-growth mechanisms, and the inclusion of brine in the sub-structure are discussed briefly.
Document Type: Research article
Publication date: 1989-01-01
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