Fluctuations of mountain glaciers in
northern Norway throughout the Holocene

Abstract

Mountain glaciers are an intrinsic part of the cryosphere and their short response times make them crucial indicators of climate change. Comprehensive investigations into long- and short-term glacier fluctuations are essential in developing reliable reconstructions of past climate variability and play a fundamental role in underpinning numerical models for the predictions of glacier behaviour in a changing climate. This thesis presents changes of mountain glaciers in central Troms and Finnmark County northern (Arctic) Norway, since the recession of the Scandinavian Ice Sheet (SIS; 14,000-11,000 cal. yrs BP), throughout the Holocene, and during the 20th and early-21st century.

A new method for identifying and mapping very small glaciers from remotely sensed imagery is developed; implementing this new approach has enabled the identification of an additional 78 ice bodies not included within prior glacier inventories. Subsequent remote sensing over the period 1989-2018 reveals considerable glacier recession, when glaciers (n = 219) shrank by 35 km2 (-35%). A subset of 15 glaciers reveals them to have lost ~69% of their area between LIA maxima and 2018 (from 10 km2 to 3.1 km2 respectively). The corollary of this is that, given 90% of the studied glaciers were <0.5 km2 in 2018, it is likely that many will melt completely before the end of the 21st century.

By combining extensive glacial and periglacial geomorphological mapping with calibrated and relative age dating, the first moraine chronology within the Rotsund Valley (Kåfjord Alps) has been established. This Holocene chronology is one of the most extensive records of small mountain glaciers across mainland Troms and Finnmark county, filling a critical gap in our knowledge on the patterns of Holocene glacier fluctuations in an area particularly susceptible to rapid climatic changes. Mountain glaciers in this region likely reached their maximum extent between ~12,000 and ~10,500 cal. yrs BP, roughly corresponding with the end of the Younger Dryas (YD; 12,900-11,700 cal. yrs BP). Subsequently glacier recession was however, interrupted by a major moraine forming event ~8,200 cal. yrs BP. Maximum Neoglacial regrowth/readvance occurred ~4,600 cal. yrs BP with the most recent glacial maximum achieved during the Little Ice Age (LIA), in the early- to mid-19th century (1814-1877).