COMPARISON OF CIRQUES IN THREE REGIONS OF ICELAND USING GIS

The purpose of this study is to complete a quantitative analysis of cirques in three regions of Iceland: Tröllaskagi, the East Fjords, and Vestfirðir. At least 483 cirques were identified in these three regions using Google Earth and the National Land Survey of Iceland Map Viewer. ArcGIS was used to measure length, width, aspect, latitude and distance to coastline of each cirque. A slope raster was constructed from the first derivative of the DEM of the study area. The headwall, cirque floor, and toewall of each cirque were determined using this raster. Paleo-equilibrium-line altitudes (ELAs) of paleo-cirque glaciers were calculated using the altitude-ratio method, the cirque floor method and a minimum point method. Average aspect was computed using an inverse tangent function based on lines constructed for the altitude-ratio method. The mean paleo-ELA values in Tröllaskagi, the East Fjords, and Vestfirðir are approximately 788 m, 643 m, and 408 m, respectively. Interpolation maps of ELA distributions in all three areas demonstrate a positive relationship between paleo-ELA and distance to coastline. There is a negative relationship between paleo-ELA and latitude in Tröllaskagi and Vestfirðir, but no relationship exists in the East Fjords. The modal orientation of the cirques in Tröllaskagi and Vestfirðir is northeast, but orientation of cirques in the East Fjords is north. Cirque length is similar in Tröllaskagi and the East Fjords, but cirques are approximately 200 m shorter in Vestfirðir. Cirque widths are similar in all three regions. Preliminary comparisons with a global dataset show that cirques in Iceland are generally smaller and more circular than cirques in other regions of the world.