Mapping and Modeling the Retreat of the Helags Cirque Glacier in Härjedalen, Sweden

Abstract

Mountain glaciers are mel􀆟ng as a consequence of global warming. A warmer climate has a direct effect on the retreat of glaciers, leading to major consequences for water supply, sea levels, tourism and local climate. By studying glaciers and their recession, we can gain an understanding of their current and past behaviour, and make predic􀆟ons and es􀆟ma􀆟ons about their future state. The Helags glacier is located in Härjedalen, Sweden, and is a retrea􀆟ng cirque glacier with numerous glacial landforms in its vicinity. No recent or detailed maps have been made and neither has an atempt to reconstruct the retreat of the glacier through modeling. This project will fill this gap by making in situ observa􀆟ons, measurements of the glacier and the surrounding landforms as well as by modeling the ice volume change over 􀆟me, with the aim to reconstruct the glacial history of the Helags glacier. Field- and drone observa􀆟ons in addi􀆟on to LiDAR data and previous mapping by the Geological Survey of Sweden (SGU) allowed for a detail geomorphological map to be made. The map presents a variety of landforms and sediments including (but not limited to) end moraines and lateral moraines, glaciofluvial sediments, stria􀆟ons, flutes and ribbed moraines. Lichenometric and Schmidt hammer measurements were taken on seven moraines below the glacier in order to inves􀆟gate and ul􀆟mately define their rela􀆟ve exposure ages. The results show a general increase in lichen size and decrease in rebound value on moraines with increased rela􀆟ve distance from the glacier, indica􀆟ng that those surfaces have likely been exposed for a longer period of 􀆟me. The modeling of the ice volume change over 􀆟me show an almost linear decrease since the beginning of the 1900s, with the glacier retaining only 24% of its 1908 volume in 2023. Forecas􀆟ng with five different temperature scenarios show a con􀆟nued retreat with the glacier consis􀆟ng of less than 3% of its 1908 volume and less than 7% of its 1908 surface area in the year 2100 for all scenarios. It is evident that the glacier has had mul􀆟ple stages of retreat, stands􀆟lls, and advances which affected the landscape by forming moraines of different intervals. It is also evident that the glacier is rapidly retrea􀆟ng and will inevitably be gone in a century’s 􀆟me. The results obtained in this study can be used to beter understand the glacial history and the rate at which the Helags glacier is, and has been, receding, while also help us to gain greater insight into similar glaciers and environments.