Crump, Sarah E.Īlpine ice varies from pure ice glaciers to partially debris-covered glaciers to rock glaciers, as defined by the degree of debris cover. ![]() Glaciation of alpine valleys: The glacier - debris-covered glacier - rock glacier continuumĪnderson, Robert S. This finding demonstrates the potential for obtaining useful paleoclimate information from rock glacier ice. The deuterium excess profile in the ice indicates that the total depth of meltwater infiltration is less than the thickness of one annual layer, suggesting that isotope values and other geochemical signatures are preserved at annual resolution. These observations are consistent with a glacial origin for the ice, substantiating the glacigenic model for rock glacier formation. Profiles of stable isotope concentrations and electrical conductivity measurements provide independent evidence for melting in association with debris layers. The debris layers are similar in appearance to those in typical alpine glaciers, reflecting concentration of debris by melting at the surface during the summer ablation season. The core contains clean, bubble-rich ice with silty debris layers spaced at roughly 20 cm intervals. Clark, D.H.Ī 9.5 m ice core was extracted from beneath the surficial debris cover of a rock glacier at Galena Creek, northwestern Wyoming. The maximum 3H concentration in ice from the Upper Fremont Glacier deposited in the Concentrations of 3H in the Upper Fremont Glacier ice core ranged from 0 TU in the ice older than 50 years to 6-12 TU in the ice deposited in the last 10 years. Tritium concentrations from the rock glacier ranged from 9.2?0.6 to 13.2?0.8 tritium units (TU) in the meltwater to -1.3?1.3 TU in the ice core. This is an order of magnitude greater than the largest measured concentration from both the Upper Fremont Glacier ice core that was not affected by weapons testing fallout and the ice core collected from the Galena Creek rock glacier. The highest concentration of 36Cl in the ice was 77 ? 2 X 106 atoms/l and was deposited during the peak of atmospheric nuclear weapons testing in the late 1950s. Purdue's PRIME Lab analyzed the ice from the Upper Fremont Glacier. Analysis of an ice core from the Upper Fremont Glacier yielded 36Cl concentrations of 1.2?0.2 X 106 and 5.2?0.2 X 106 atoms/l for pre- 1940 ice and between 2 X 106 and 3 X 106 atoms/l for post-1980 ice. The ice-core 36Cl concentrations from Galena Creek ranged from 3.4?0.3 X 105 to 1.0?0.1 X 106 atoms/l. Meltwater samples from three sites on the rock glacier yielded 36Cl concentrations that ranged from 2.1 ? 1.0 X 106 to 5.8?0.3 X 106 atoms/l. ![]() Measurements of chlorine-36 (36Cl), tritium (3H), sulphur-35 (35S), and delta oxygen-18 (?18O) were compared to similar measurements from an ice core taken from the Upper Fremont Glacier in the Wind River Range of Wyoming collected in 1991-95. A 9.4 m ice core and meltwater were collected in 19 at the glacigenic Galena Creek rock glacier in Wyoming's Absaroka Mountains. ![]() Determining the origin of the meltwater from glaciers through isotopic analysis can provide information about such things as the character and distribution of ablation on glaciers. Meltwater runoff from glaciers can result from various sources, including recent precipitation and melted glacial ice. Isotopic composition of ice cores and meltwater from upper fremont glacier and Galena Creek rock glacier, WyomingĭeWayne, Cecil L.
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