Spatial modeling of permafrost distribution using rock glacier inventories, topographic attributes and temperature data in the semiarid Andes, Chile
Abstract
Statistical-empirical models have been widely used to estimate the spatial distribution of permafrost in the European Alps and North America using topographic, climatic data and geomorphic indicators of permafrost (i.e. rock glaciers). At present, little knowledge about mountain permafrost distribution is available for the Andes. As a first approximation of permafrost distribution, a logistic regression model was fitted to predict rock glacier activity status. The model is based on explanatory variables elevation and potential incoming solar radiation (PISR) derived from an ASTER G-DEM v. 2 digital elevations model and air temperature data in the Chilean Andes between 29 and 34°S. Rock glacier activity status (intact versus fossil) was obtained from several recent rock glacier inventories and is based on the interpretation of aerial photographs or satellite imagery with a resolution higher than 5 m. Constant lapse rates of temperature are obtained for several weather stations in the study region. These are used to estimate the change in temperature with elevation based on the digital elevation model. The model's predictive performance was evaluated using the area under the ROC curve. As a preliminary result using a probability threshold of 0.5, mountain permafrost may be present in up to 21% (1510 km2) of the Huasco watershed (29°S) located in the northern part of the study area. Considering a threshold > 0.75, about 12% (709 km2) of this watershed may be underlain by mountain permafrost. As next steps toward a permafrost distribution model, sources of bias related to the thermal offset and displacement of rock glaciers will be eliminated, and downscaling as well as spatial interpolation approaches will be evaluated in order to replace elevation as a proxy variable with estimates of mean annual air temperature.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.C13D0647A
- Keywords:
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- 0702 CRYOSPHERE / Permafrost;
- 0722 CRYOSPHERE / Rock glaciers;
- 0772 CRYOSPHERE / Distribution;
- 0798 CRYOSPHERE / Modeling