Quantification of historical landscape change on the foreland of a receding polythermal glacier, Hørbyebreen, Svalbard

The assessment of multidecadal scale change in a polythermal glacial landsystem in the high Arctic is facilitated by a quantitative approach that utilises time series of aerial photographs, satellite images, digital elevation models, and field geomorphological mapping. The resulting spatiotemporal analysis illustrates a transition from glacial to proglacial/paraglacial conditions indicating that (1) the areal coverage of ice between the maximum LIA extent and 2013 decreased from 29.35 to 16.07 km2, which is a reduction in the glacierized area in the catchment from 62% to 34%; (2) the ice volume loss in the proglacial area amounted to 214.9 (±3%) million m3, which was attributed mostly to ablation of the glacier snout but to a lesser extent the degradation of ice-cored landforms; (3) the transition from areas formerly covered by glacier ice to ice-cored moraines, glacifluvial deposits, and other landforms was the most intense in the period 1990–2013; (4) two end member scenarios (polythermal glacial landsystem domains) evolve during glacier recession, each one dictated by the volume of debris in englacial and supraglacial positions, and include (a) subglacial surfaces (limited englacial and supraglacial debris) related to temperate basal ice and (b) ice-cored lateral moraines and moraine-mound complexes (significant supraglacial debris accumulations) related to marginal cold-based ice. An additional assemblage of geometric ridge networks (discrete or linear englacial and supraglacial debris concentrations) relates to crevasse and hydrofracture infill branching out from an esker complex and is indicative of either surging or later rapid release of pressurised meltwater from temperate to cold-based parts of the former glacier snout.