SPATIAL MODELLING OF PALSA MIRES 1373 Copyright © 2004 John Wiley & Sons, Ltd. Earth Surf. Process. Landforms 29, 1373–1387 (2004) Earth Surface Processes and Landforms Earth Surf. Process. Landforms 29, 1373–1387 (2004) Published online 10 September 2004 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/esp.1099 * Correspondence to: M. Luoto, Finnish Environment Institute, Research Department, Research Programme for Biodiversity, PO Box 140, FIN-00251 Helsinki, Finland. E-mail: Miska.Luoto@ymparisto.fi SPATIAL MODELLING OF PALSA MIRES IN RELATION TO CLIMATE IN NORTHERN EUROPE MISKA LUOTO, 1,2 * STEFAN FRONZEK 2 AND FRIEDA S. ZUIDHOFF 3 1 CSIRO, Sustainable Ecosystems, Wembley, Western Australia, Australia 2 Finnish Environment Institute, Helsinki, Finland 3 Department of Earth Sciences, Physical Geography, Geocentrum, Uppsala, Sweden Received 29 August 2003; Revised 8 March 2004; Accepted 30 March 2004 ABSTRACT Palsa mires are mire complexes that occur in the Northern Hemisphere, representing one of the most marginal permafrost features at the outer limit of the permafrost zone. A climate-based spatial model is presented for the distribution of palsa mires in northern Europe. The model is based on an extensive spatial data of palsa mires and climatological variables from 1913 grid cells in an area of c. 240 000 km 2 . Generalized linear modelling (GLM) with curvilinear and interaction terms is used to derive the palsa mire–climate relationships. The final model correctly classified 77·6 per cent of the palsa mire presence squares. The results indicate a positive association of the distribution of palsa mires with increasing frost number and continentality, whereas precipitation and temperature showed a negative correlation with the distribution of palsa mires. Additionally, interaction of thawing degree days and summer time precipitation showed a negative association. Climatologically, the optimum areas of palsa mires occur in areas of low precipitation (<450 mm) and a mean annual temperature between -3 °C and -5 °C. Potential reasons for the performance of the model and the sensitivity of palsa mires to climate change are discussed. The application of a GIS-based generalized linear modelling as used here provides a versatile method to study the distribution of different geomorphological phenomena across climatological gradients. Copyright © 2004 John Wiley & Sons, Ltd. KEY WORDS: climate; generalized linear modelling; GIS; palsa mire; permafrost INTRODUCTION The analysis and modelling of geomorphological processes and landforms in relation to climate is one of the central issues in modern physical geography. The increased availability of powerful statistical techniques and GIS tools has led to the rapid development of spatial models in geomorphology (Atkinson et al., 1998; Rowbotham and Dudycha, 1998; Gruber and Hoelzle, 2001; Nelson et al., 2001; Luoto and Seppälä, 2002). Climate, in combination with other geographical factors (e.g. hydrology, topography, geology and soil type), has been widely used to explain distribution patterns of different periglacial processes and landforms around the world (Washburn, 1979; Williams and Smith, 1989). In this paper, we provide a detailed quantitative description of the distribution of palsa mires in a large region of northern Europe. Palsa mires are mire complexes that occur in the Northern Hemisphere, representing one of the most marginal permafrost features at the outer limit of the permafrost zone (Seppälä, 1988). Palsas are characteristic geomorphological features of subarctic mire landscapes. Palsas typically rise to a height of 0·5– 10 m above the mire surface (Åhman, 1977; Seppälä, 1986). They are usually composed largely of peat and ice crystals but examples occur with mainly mineral soil, with or without a substantial surface organic layer (Williams and Smith, 1989). Palsas are good indicators of permafrost in mires and they can easily be identified from aerial photographs (Luoto and Seppälä, 2002). The morphology varies from dome-shaped to elongated ridge forms, and from large single plateaux to palsa complexes of extremely varied form (Åhman, 1977; Seppälä, 1988). The distribution of palsa mires distribution in Europe includes the Kola Peninsula in Russia, Norway, Finland, Sweden and