GIS Analysis of Cirques on Vestfirðir, Northwest Iceland: Implications for Paleoclimate
This presentation was given at the 125th Anniversary Annual Geological Society of America Meeting in Denver, Colorado, October 27,30, 2013.
A regional analysis of cirques on Vestfirðir, northwest Iceland was conducted using a Geographic Information System (GIS). The length, width, elevation, latitude, aspect, and distance to coastline of cirques were quantified using ArcGIS. The topographic analysis revealed at least 100 cirques on western and northern Vestfirðir, Iceland. Median cirque length is 460 m and median cirque width is 700 m. The modal orientation of the aspect of cirques is northeast, with secondary modes to the north and northwest. Cirques at low elevations are more abundant close to the modern coastline, while cirques further from the coastline are present at high elevations. Three techniques were used to reconstruct past equilibrium-line altitudes (ELAs) of cirque glaciers: the cirque-floor method, the altitude-ratio method, and the accumulation-area ratio method. The largest range of past ELAs is generated from the cirque-floor method with values from 40 m up to 730 m. The median ELA value is approximately 420 m, indicating snowline depression of at least 240 m compared to the modern snowline of the Drangajökull ice cap on eastern Vestfirðir. A strong positive relationship is observed between past ELA values and distance to the modern coastline demonstrating the importance of access to a moisture source for glacier survival. Based on the small size of cirque glaciers on Vestfirðir, it is likely that even minor fluctuations in the Irminger Current and the East Greenland Current influence cirque glaciation.