Quantitative analyses of cirques on the Faroe Islands: evidence for time transgressive glacier occupation

Abstract

This study presents the first analysis of ice‐free cirques on the Faroe Islands using a Geographical Information System (GIS) and the Automated Cirque Metric Extraction (ACME) tool. The length, width, area, circularity, mean aspect, mean slope, and elevation range, minimum, and maximum were calculated using ACME. Cirque distance to coastline was measured using ArcGIS. A total of 116 cirques were identified. Mean cirque length is 950 m and mean cirque width is 890 m. Average cirque area is 0.8 km2 and mean elevation is 386 m a.s.l. The modal orientation of the aspect of cirques is north‐northeast, with a vector mean of 7° and mean resultant length of 0.09. Aspect data have large dispersion, which shows evidence of cloudy ablation seasons in the past. The dispersion in aspect may also be related to the time transgressive nature of glacier occupation in these cirques. Past equilibrium‐line altitudes (ELAs) of cirque glaciers reconstructed with the minimum point method resulted in a mean palaeo‐ELA of 213 m a.s.l. Positive, linear relationships are observed between palaeo‐ELA and cirque distance to coastline. There are at least two possible interpretations of this relationship: (i) that the cirque formation is dependent on pre‐existing topography with cirques forming at the head of valleys, which occurs at higher elevations further inland, and (ii) that this relationship demonstrates the importance of access to moisture for glacier survival. A combination of both interpretations is also possible. Positive linear relationships are also observed between longitude and palaeo‐ELA indicative of palaeo‐precipitation patterns along an east–west gradient. Cirques on the Faroe Islands are smaller in length and width and present at lower elevations compared to cirques located in other regions of the world. The timing of glacial occupation in these cirques is not known, and the landforms likely formed over multiple glaciations.

Inherited terrestrial cosmogenic nuclides in landscapes of selective glacial erosion: lessons from Lochnagar, Eastern Grampian Mountains, Scotland

“…Application of the Younger Dryas headwall retreat rate suggests that a total of ~400 ka of active glaciation was necessary for erosion of Lochnagar Corrie. Hence, in common with many cirques (Ruszkiczay-Rüdiger et al, 2021, Crest et al, 2017, Wallick and Principato, 2020, erosion of the Lochnagar Corrie was incremental through multiple Pleistocene glaciations.…”

ACME2: An extended toolbox for automated cirque metrics extraction

“…This requires three inputs: cirque outlines (polygons), threshold midpoints, and a DEM. This toolbox has been used to extract cirque metrics and infer palaeoclimate conditions in various settings worldwide, including: Britain and Ireland (Barr et al, , 2019, the Guadarrama and Somosierra mountains in Spain (Pedraza et al, 2019), the Faeroe Islands (Wallick and Principato, 2020), High Mountain Asia ( Zhang et al, 2020( Zhang et al, , 2021Li et al, 2023), and Antarctica (Barr et al, 2022(Barr et al, , 2023. Use of DEMs allowed ACME to calculate new descriptors such as hypsometric integral, mean slope and 3D area.…”

Controls on the altitude of Scandinavian cirques: What do they tell us about palaeoclimate?

“…Therefore, palaeo-ELAs are important as palaeoclimatic indicators because they are the result of changed precipitation and temperature, which control glacial surface mass balance over time and cirques are one way of obtaining palaeo-ELAs (e.g. Torsnes et al, 1993;Kern and László, 2010;Barr and Spagnolo, 2015a;Barr and Spagnolo, 2015b;Barr et al, 2017;Pearce et al, 2017;Ipsen et al, 2017;Wallick and Principato, 2020).…”

“…One of the simplest ways is to map and measure cirque floor altitudes (CFAs) (e.g. Torsnes et al, 1993;Kern and László, 2010;Barr and Spagnolo, 2015a; Barr and Spagnolo, 2015b;Barr et al, 2017;Pearce et al, 2017;Ipsen et al, 2017;Wallick and Principato, 2020). The premise behind this approach is that cirques (bowl-shaped depressions, characterised by steep headwalls and flat or overdeepened floors sometimes occupied by small lakes; Evans and Cox, 1974;Vilborg, 1977;Fredin et al, 2013) are formed where glaciers develop and erode their underlying bedrock.…”