ABSTRACT: Can molar gas ratios positively identify the nature and origin of massive ground ice of Herschel Island, Yukon?

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How did it get to be underground in the first place? Did the source water trickle down from the melting snows or up well from subterranean springs?” Mackay, 1972 An exciting new tool has been developed in recent years that enables geocryologists to accurately identify the origin and nature of massive ground ice features. The molar ratios of O2, N2 and Ar gases entrapped in massive ground ice is a novel, periglacial fi eld technique that results in a positive disassociation between buried glacial and nonglacial intrasedimental ice (Lacelle et al., 2007 and Cardyn et al., 2007). Massive ground ice, large tabular ice bodies with a volumetric ice content exceeding 95%, is a unique permafrost feature that persists throughout permafrost landscapes (International Permafrost Association, 1998). Massive ground ice features, discovered in the headwalls of retrogressive thaw slumps on Herschel Island, Yukon, have been analyzed extensively in order to comprehend the structure, composition and spatial extents (Pollard, 1990). However, the origin of this buried ice, be it buried glacial or non-glacial intrasedimental ice, is a fundamental question that has yet been fully understood. To understand the origin of massive ground ice features is to understand the paleoclimates and environments that spawned their creation. Moreover, ground ice features have a major influence on the geomorphology of permafrost landscapes and directly control rates of coastal erosion, active layer depth migrations and thermokarst activity, all of which are projected to increase under many climate change scenarios. The established research sites of Herschel Island offer a unique opportunity to employ new scientific methods to understand this longstanding question. Our research team, along with scientists at the University of Ottawa, have begun to analyze the geochemical composition of this ice including the pH, liquid conductivity, anions/cations, tritium and deuterium and gravimetric ice contents. Preliminary pH and conductivity studies have found the sampled massive ice bodies to be particularly ice rich and originated from ground water sources. Tritium and deuterium findings suggest that the majority of ice is intrasedimental in origin and of Pleistocene age. Such findings are crucial if we are to understand the modern architecture of Herschel Island and to accurately project the island’s future geomorphology.

Bibliography of Canadian Geomorphology