ABSTRACT: Ground surface temperature history inferred from a borehole temperature profile through the permafrost in northern Quebec: Evidence for recent warming.

CGRG Bibliography of Canadian Geomorphology
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Abstract

A 430 meters temperature depth profile in permafrost was measured at the Raglan mine located in the Cape Smith foldbelt at the tip of the Ungava peninsula, south of Deception Bay in Northern Quebec. The site is located on a high plateau (600 m) and is mostly a barren rock desert with minimal vegetation cover. The borehole had been fitted with a capped steel pipe filled with silicone oil and measurements were made more than 15 months after drilling was completed, insuring that thermal equilibrium had been reached. In order to infer the ground surface temperature history (GSTH), an inversion was performed using an algorithm based on singular value decomposition. The presence of instabilities due to the inversion technique made impossible the identification of an unusual cooling period in Northern Quebec between the 1940s and 1990s described by numerous authors. Using forward modeling techniques, we computed different warming/cooling scenarios numerically in order to reproduce both the experimental data and other researchers surface temperatures results. None of the models that fit the experimental data indicate a cooling of ground temperatures at any time during the past 150 years. We inferred that the total warming of the past 150-200 years ranges between 1.5 and 2.5 degrees.

Bibliography of Canadian Geomorphology