Timing of Little Ice Age maxima and subsequent glacier retreat in northern Troms and western Finnmark, northern Norway

Abstract

Glaciers are important indicators of climate change, and recent observations worldwide document increasing rates of mountain glacier recession. Here we present approximately 200 years of change in mountain glacier extent in northern Troms and western Finnmark, northern Norway. This was achieved through (1) mapping and lichenometric dating of major moraine systems within a subset of the main study area (the Rotsund Valley) and (2) mapping recent (post-1980s) changes in ice extent from remotely sensed data. Lichenometric dating reveals that the Little Ice Age (LIA) maximum occurred approximately 1814 (±41 years), which is before the early twentieth-century LIA maximum proposed on the nearby Lyngen Peninsula but younger than LIA maximum limits in southern and central Norway (mid-eighteenth century). Between LIA maximum and 1989, a small sample of measured glaciers (n = 15) shrank a total of 3.9 km2 (39 percent), and those that shrank by more than 50 percent are fronted by proglacial lakes. Between 1989 and 2018, the total area of glaciers within the study area (n = 219 in 1989) shrank by approximately 35 km2. Very small glaciers (<0.5 km2) show the highest relative rates of shrinkage, and 90 percent of mapped glaciers within the study area were less than 0.5 km2 in 2018.