Modelling geomorphic response to climatic change Nicole J. Couture & Wayne H. Pollard Received: 17 November 2003 / Accepted: 10 May 2007 / Published online: 10 October 2007 # Springer Science + Business Media B.V. 2007 Abstract This paper develops a three-step thaw model to assess the impact of predicted warming on an ice-rich polar desert landscape in the Canadian high Arctic. Air temperatures are established for two climate scenarios, showing mean annual increases of 4.9 and 6.5°C. This leads to a lengthening of the summer thaw season by up to 26 days and increased thaw depths of 12–70 cm, depending on the thermal properties of the soil. Subsidence of the ground surface is the primary landscape response to warming and is shown to be a function of the amount and type of ground ice in various cryostratigraphic units. In areas of pore ice and thin ice lenses with a low density of ice wedges, subsidence may be as much as 32 cm. In areas with a high density of ice wedges, subsidence will be slightly higher at 34 cm. Where massive ice is present, subsidence will be greater than 1 m. Landscape response to new climate conditions can take up to 15 years, and may be as long as 50 years in certain cases. 1 Introduction Permafrost is ground that remains at or below 0°C for at least two consecutive years (International Permafrost Association 1998). It underlies almost one quarter of the Earth’ s landmass (French 1996). Much of the world’ s permafrost terrain is at or near its limit of thermal stability and even small changes in climate are likely to trigger a response in the landscape. According to various climate models, warming is projected to be two to three times greater in the polar regions than elsewhere, with temperature increases in the Canadian Arctic predicted to be from 2 to 15°C before the end of this century [Hengeveld 2000; Arctic Climate Impact Assessment (ACIA) 2005]. Anisimov and Nelson (1997) predicted that in the northern hemisphere, the area underlain by permafrost could be reduced by up to 22% by the year 2050, and Lawrence and Slater (2005) suggest that it Climatic Change (2007) 85:407–431 DOI 10.1007/s10584-007-9309-5 N. J. Couture (*) : W. H. Pollard Department of Geography and Global Environmental and Climate Change Centre, McGill University, 805 Sherbrooke St. W., Montreal, Quebec, Canada H3A 2K6 e-mail: nicole.couture@mail.mcgill.ca