CGRG Bibliography of Canadian Geomorphology
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Author : Chouinard, C.; Fortier, R.; and Mareschal, J-C.
Date : 2007.
Title : Ground surface temperature history inferred from temperature depth profiles in Northern Quebec: Evidence for recent warming.
Publication : CMOS, CGU, AMS Congress 2007. "Air, Ocean, Earth and Ice on the Rock". May 28 - June 1, 2007. St. John's Congress Centre, Newfoundland and Labrador, Canada.
Issue :
Page(s) : C02-2B5 .7.
Abstract
Four temperature profiles were measured in deep boreholes in permafrost at the Raglan mine located in the Cape Smith foldbelt near the northern tip of the Ungava peninsula, Northern Quebec. The site is a barren rock desert on an elevated plateau. The boreholes were logged in September 2006 more than three years after drilling was completed, allowing return to thermal equilibrium. Thermal conductivity measurements were made on core samples. Radiogenic heat production is small and can be neglected. The temperature profiles show deviations from steady state due to recent variations in ground surface temperature (< 300 years). Three methods were used to infer the ground surface temperature history (GSTH): 1) forward modeling where the assumed GSTH is used to calculate the temperature anomalies of permafrost and compare with the measured ones, 2) a standard inversion with an algorithm based on singular value decomposition, and 3) a Monte Carlo inversion. The results show a strong warming between the mid-1700s and the early 1900s followed by a cooling episode which lasted approximately 50 years. The ground surface at Raglan has experienced a 1.7°C warming in the past century and a 2.7°C warming since the minimum of the Little Ice Age (late 1700s). Between the 1920s and the 1970s, a cooling of 0.3°C has occurred in the region with temperatures remaining relatively stable until the mid-1990s. The borehole measurements suggest 1.5°C ground surface temperature warming over the past 10 years.
Bibliography of Canadian Geomorphology