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Abstract:
Most glaciers in the world reached their Holocene maximum extent during the so-called Little Ice Age (LIA). Glacier volume change since the LIA requires information on former glacier extent and surface elevation. Whereas extents can be digitized from trimlines and moraines, former glacier surfaces need to be reconstructed. Recent studies have interpolated the surface from elevation values along the former outline. However, there has been no comparison or uncertainty analysis of various surface reconstruction and interpolation methods.This study evaluates various spatial interpolation methods and the impact of input datasets on glacier surface reconstruction. Modern glacier surfaces were replicated using a recent DEM, and the methods were tested on a sample of 90 glaciers in southern Novaya Zemlya and 266 glaciers in the Aletsch region of Switzerland. The Natural Neighbour and Topo to Raster interpolation methods available in ESRIs ArcGIS performed best, but all methods struggled with the convex curvature of glacier surfaces in the ablation region.We complemented existing methods with centre point elevations derived from lateral elevation changes, resulting in a more realistic representation of the former glacier surface. Additionally, we developed a surface reconstruction method that is suitable for ice caps without lateral moraines. Neglecting the smaller elevation changes in the accumulation region could significantly affect derived glacier volume changes. Recent research (DOI: 10.1038/s41586-021-03436-z) indicates that the average elevation change rate over the last two decades (-0.8 m a-1) for Novaya Zemlya was significantly higher than from 1850 to 2018 (-0.14 m a-1) .
