An ~1899 glacier inventory for Nordland, northern Norway, produced from historical maps

Abstract

Glaciers depicted on old maps reveal their historical extents, before the advent of aerial and satellite remote sensing. Digital glacier inventories produced from these maps can be employed in assessments of centennial-scale glacier change. This study reconstructs the ~1899 (covering the period 1882–1916) glacier extent in Nordland, northern Norway, from historical gradteigskart maps, with an emphasis on examining the accuracy of the mapped glaciers. Glacier outlines were digitised from georectified scans of the analogue maps in a raster graphics editor and were subsequently inventoried in a GIS. The accuracy of the historical glacier extent was established from written descriptions and landscape photographs created during the original field surveys, and further validated against independent glacier outlines of (1) the maximum Little Ice Age extent derived from geomorphological evidence, and (2) the 1945 extent derived from vertical aerial photographs. An overall uncertainty of ±17% is associated with our inventory. Nordland's glaciers covered an area of 1712 ± 291 km2 in 1899. By 2000, total ice cover had decreased by 47% (807 ± 137 km2) at a rate of 6% 10 a−1 (80 ± 14 km2 10 a−1). The approach presented here may serve as a blueprint for future studies intending to derive glacier inventories from historical maps.

Reconstructing the Little Ice Age extent of Langfjordjøkelen, Arctic mainland Norway, as a baseline for assessing centennial-scale icefield recession

“…that region receded in area by 47% between ca. 1899 and 2000 (Weber et al 2020). This value is similar to Langfjordjøkelen's 50% area reduction between 1925 and 2006 but represents a considerably longer measurement interval.…”

“…This value is similar to Langfjordjøkelen's 50% area reduction between 1925 and 2006 but represents a considerably longer measurement interval. When icefield-type glaciers were compared alone, the nine largest Nordland icefields decreased in area by only 27% in the period 1899-2000 (Weber et al 2020), which is only about half the percentage change that we observed at Langfjordjøkelen. Stokes et al (2018) assessed long-term glacier change in Lyngen since the local LIA maxima in ca.…”

“…(An assessment of historical map accuracy in Nordland [ Fig. 1a] by Weber et al [2020] generally showed a higher quality of the glacier mapping than here at Langfjordjøkelen; in Nordland, mapping errors and the inclusion of ice-marginal snow seemed to be more of a problem at smaller glaciers.) An additional possibility is that prolonged lake ice at Jiehkkejávri after a severe winter and a cool spring may have been misinterpreted as an outlet glacier by the surveyors.…”

“…Reconstructing the LIA extent of Norwegian glaciers and icefields is done by mapping the clear glacial geomorphological evidence at the margins of the modern ice masses, and in particular the stark boundaries between fresh, glacially eroded terrain and weathered, vegetated areas (e.g., Ballantyne 1990;Stokes et al 2018;Weber et al 2019;Weber et al 2020). Following a standard approach outlined by Chandler et al (2018), we mapped glacial landforms and terrain boundaries remotely in ArcGIS from high-resolution (0.25 m) digital colour vertical aerial photographs captured on 20-21 August 2015 (acquired from http://norgeibilder.no/; Table 1).…”

Aldegondabreen glacier change since 1910 from structure-from-motion photogrammetry of archived terrestrial and aerial photographs: utility of a historic archive to obtain century-scale Svalbard glacier mass losses

“…Topographic maps older than 1936 have been used to draw profiles or to calculate glacier extent (Liestøl, 1969; Nuttall and others, 1997; Pälli and others, 2003; Flink and others, 2015, 2018). However, the associated errors are large and sometimes difficult to quantify, although the workflow suggested by Weber and others (2020) may help in standardising these errors. Since no similar historic terrestrial reconstructions have been done on Svalbard before 1936, the results of this study lack a good comparison.…”