Abstract
Alpine permafrost occurrence in maritime climates has received little attention, despite suggestions that permafrost may occur at lower elevations than in continental climates. To assess the spatial and altitudinal limits of permafrost in the maritime Southern Alps, we developed and tested a catchment-scale distributed permafrost estimate. We used logistic regression to identify the relationship between permafrost presence at 280 active and relict rock glacier sites and the independent variables a) mean annual air temperature and b) potential incoming solar radiation in snow free months. The statistical relationships were subsequently employed to calculate the spatially-distributed probability of permafrost occurrence, using a probability of ≥ 0.6 to delineate the potential permafrost extent. Our results suggest that topoclimatic conditions are favorable for permafrost occurrence in debris-mantled slopes above ~ 2000 m in the central Southern Alps and above ~ 2150 m in the more northern Kaikoura ranges. Considering the well-recognized latitudinal influence on global permafrost occurrences, these altitudinal limits are lower than the limits observed in other mountain regions. We argue that the Southern Alps’ lower distribution limits may exemplify an oceanic influence on global permafrost distribution. Reduced ice-loss due to moderate maritime summer temperature extremes may facilitate the existence of permafrost at lower altitudes than in continental regions at similar latitude. Empirical permafrost distribution models derived in continental climates may consequently be of limited applicability in maritime settings.
Highlights
Alpine permafrost distribution studies have focused predominantly on continental regions, building on pioneering work in the European Alps (e.g., Haeberli, 1975; Barsch, 1978) and the North American Cordilleras (e.g., Wahrhaftig and Cox, 1959; Ives and Fahey, 1971; Harris and Brown, 1978)
382 talus-derived rock glaciers were mapped in the central Southern Alps and the Inland Kaikoura Range (Figure 4; see Supplementary Material for inventory in tabular form)
The observed variations in the location of active and relict rock glacier sites according to altitude and aspect support the use of the underlying environmental controls mean annual air temperature (MAAT) and solar radiation for predictive permafrost modeling at catchment scale
Summary
Alpine permafrost distribution studies have focused predominantly on continental regions, building on pioneering work in the European Alps (e.g., Haeberli, 1975; Barsch, 1978) and the North American Cordilleras (e.g., Wahrhaftig and Cox, 1959; Ives and Fahey, 1971; Harris and Brown, 1978). An oceanic control on permafrost distribution limits has been occasionally suggested in the past. Cheng (1983) found altitudinal permafrost limits in Western China were lower in areas of lower continentality due to the effect of cloud cover (more frequent in maritime climates) at latitudes below 40◦N. Gorbunov (1978) reported a general trend of lower mountain permafrost limits in littoral regions without elaborating on Permafrost in Maritime New Zealand possible controls. Matsuoka (2003) documented lower permafrost limits in Asian high mountain areas of humid continental and pacific climate than in arid continental climates. Gruber and Haeberli (2009) suggested an increase in elevation of permafrost limits on gentle slopes toward maritime areas, where thick insulating snowpacks result in warmer temperatures in the underlying substrate. More information on permafrost distribution in maritime settings is needed to further explore the existing, partly contradictory, understanding of permafrost occurrence in maritime areas
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