Ground ice investigation in the Far Northwest of Canada.

• Main Author: Lacelle, Denis.
• Format: Thesis
• Language: unknown
• Published: Université d'Ottawa / University of Ottawa 2002
• Subjects: Physical Geography.; Canada; Richardson Mountains; Yukon; Ice; Ice Sheet; permafrost
• Online Access: https://dx.doi.org/10.20381/ruor-11284; http://www.ruor.uottawa.ca/handle/10393/6455

Ground ice formation in the Far Northwest of Canada was investigated using stable isotopes (delta18O and deltaD) and 14C dating. These have proven to be valuable tools when inferring the origin of ground ice bodies. The major findings are: (1) During the Late Pleistocene, massive tabular ground ice bodies formed extensively in the Willow River area, Richardson Mountains. These ice bodies are currently exposed in the headwalls of retrogressive thaw slumps as a result of climate warming. Two units were recognized on the basis of ice structure: a debris-rich ice overlain by a diamicton. The debris-rich ice, characterized by low delta 18O values (-30‰ to -27‰), is believed to have formed by in situ freezing of subglacial meltwater derived from the Laurentide ice sheet. The meltwater flowed through water-saturated till between relict and aggrading permafrost. A decrease in subglacial meltwater flow from the ice sheet and a decrease in enthalpy transfer from the meltwater caused the freezing of the meltwater within the proglacial water-saturated till. The ice in the diamicton is characterized by relatively high delta 18O values (-26‰ to -20‰) and formed from the freezing of isotopically enriched Holocene waters. (2) In the northern Yukon, a delta18O analysis of surface and subsurface ice was undertaken. The results indicate that the delta18O composition of the various ice types is dependent upon a number of factors, such as surface air temperature, relative humidity and freezing rates. Holocene age waters are characterized by delta18O values >-27‰, while Pleistocene age waters have delta18O values <-27‰, indicating colder air temperature at the time of precipitation. The effect of evaporation on the isotopic composition of water was best observed on open surfaces where enrichment in the order of 5--11‰ in 18 O was measured.