Extent and elevation changes of Tröllaskagi glaciers, North Iceland

Abstract

There are 170 glaciers on the Tröllaskagi peninsula in North Iceland. These range in size, from ~6 km2 for the larger valley glaciers, to <0.1 km2 for some of the smallest cirqueglaciers. A number of glaciers have significant amounts of debris cover, in some cases almost the entire surface area, alongside a number of rock glaciers. There is also a large amount of buried ice, permafrost, and perennial snow and ice above 800-900 m a.s.l in most areas. This project aims to map the outlines of glaciers over the whole peninsula for 2022and provide these for Icelandic and global outline inventories. Then, the main focus is on the central study area, to map outlines for 2016 and compare in detail the 6 years for changes in area, alongside differences in elevation to further highlight any changes, whether retreat, advance, or possible surging.Glacier outlines for 144 glaciers were mapped for the year 2022, and comparisons of outlines between 2016 and 2022 were done for 53 glaciers. Elevation difference was calculated by comparing digital elevation models of glaciers in 2016 and 2022 to allow for more knowledge on changes of these glaciers. A majority of these glaciers are retreating, at varying rates, with only 4 glaciers experiencing advance, such as Hofsdalsjökull, having the greatest area increase of 0.04 km2. The larger valley glaciers within the study have larger differences, with Héðinsdalsjökull experiencing -0.23 km2 loss in area, or 4.8% of its area. Smaller glaciers, however, have a larger percentage of area loss, such as Vesturdalsjökull 2 with -43.5% area loss. Elevation loss was greatest for larger glaciers, such as Tungnahryggsjökull eystri and vestri which have elevation losses exceeding 10 m in their snouts. Some of the smaller cirque glaciers also experience pronounced elevation loss, which for their size is significant as many are already very small, such as Vesturdalsjökull 2 with -6 m. Glaciers with very little elevation changes from 2016-2022, or even positive changes were Grýtudalsjökull vestri and eystri, Tjarnhólajökull, and Vatnsdalsjökull eystri 2, and those further north in the central study area experience less negative changes or closer to 0 m of change.Two surge-type glaciers have been observed, Vatnsdalsjökull eystri 1 and Vífilsfjallsjökull. These have not previously been identified as surge-type, so are added to the list of surging glaciers on the Tröllaskagi peninsula which include Teigarjökull, Bægisárjökull, Búrfellsjökull and Vífilsjökull vestri/eystri 2. Glaciers on Tröllaskagi are considered some of the smallest surge-type glaciers in the world, with Vífilsfjallsjökull being the smallest among these, at only around 0.13 km2, it is likely the smallest surge-type glacier observed.