GIS analysis of cirques on Vestfirðir, northwest Iceland: implications for palaeoclimate

Abstract

This study presents the first regional analysis of cirques on Vestfirðir, NW Iceland, using a Geographical Information System (GIS). The length, width, elevation of cirque-floor, latitude and the distance to the modern coastline (both ocean and fjord coastlines) of cirques were quantified using ArcGIS. The topographical analysis revealed a total of 100 cirques on western and northern Vestfirðir. Several additional cirques are present, but they had poorly defined toewalls, making the cirque-floor difficult to identify. Mean cirque length is 515 m and mean cirque width is 752 m. The modal orientation of the aspect of cirques is northeast, with a strong secondary mode to the northwest. Cirques at low elevations are more abundant close to the ocean, whereas cirques further from the ocean 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 up to 730 m. Mean past ELA values range from ∼395 to 423 m depending on the method used to reconstruct former ELAs. A strong positive relationship is observed between past ELA values and distance to the ocean demonstrating the importance of access to a moisture source for glacier survival. This relationship is stronger than the relationship between former ELAs and latitude. Based on the small size of cirque glaciers, it is likely that even minor fluctuations in the Irminger Current and the East Greenland Current influence cirque glaciation on Vestfirðir.

Understanding controls on cirque floor altitudes: Insights from Kamchatka

“…Despite this, a number of studies have analysed cirque floor altitudes across specific regions (e.g., Linton, 1959;Davies, 1967;Derbyshire, 1963;Peterson and Robinson, 1969;Hassinen, 1998;Evans, 1999;Anders et al, 2010;Principato and Lee, 2014) and at a near-global scale (e.g., Mitchell…”

“…However, though this trend is found in a number of mountain ranges globally (see Evans, 2006c), and applies to modern glaciers (see Evans and Cox, 2005;Evans, 2006bEvans, ,c, 2011, it is not ubiquitous (see Evans, 1999;Evans and Cox, 1995). Another characteristic common to many cirque populations globally, is that floor altitudes are found to increase inland (e.g., Peterson and Robinson, 1969;Hassinen, 1998;Principato and Lee, 2014). In many cases, this is attributed to the role of precipitation in regulating the altitude of former glaciers, though the potential influence of other, non climatic, factors is also recognised (see Peterson and Robinson, 1969;Hassinen, 1998;Principato and Lee, 2014).…”

“…Another characteristic common to many cirque populations globally, is that floor altitudes are found to increase inland (e.g., Peterson and Robinson, 1969;Hassinen, 1998;Principato and Lee, 2014). In many cases, this is attributed to the role of precipitation in regulating the altitude of former glaciers, though the potential influence of other, non climatic, factors is also recognised (see Peterson and Robinson, 1969;Hassinen, 1998;Principato and Lee, 2014). For example, in SW Tasmania, Peterson and Robinson (1969), found evidence of an inland increase in cirque floor altitudes, and attribute this to an inland palaeoprecipitation gradient.…”

ACME, a GIS tool for Automated Cirque Metric Extraction

“…Many recent papers, in particular, have started to take full advantage of high resolution Digital Terrain Models (DTM) and Geographical Information Systems (GIS), allowing for rapid and improved analyses of cirque size and shape from large datasets (e.g. Anders et al, 2010;Principato and Lee, 2014). However, each metric analysed often requires a separate tool, or a combination of tools, that are not necessarily easy to find, implement, and combine for non-GIS experts.…”

“…Spatial trends in any of the ACME output metrics in relation to lithology, structure and tectonics can also be used to understand geological controls on cirque development and post-glacial modifications (Principato and Lee, 2014). Finally, the study of hypsometric variables, when compared to former equilibrium line altitudes, has been used to test feedbacks between glacial erosion and uplift in mountainous regions worldwide (Foster et al, 2008, Egholm et al, 2009, Barr and Spagnolo, 2014).…”