Landscape evolution in proglacial areas based on examples from central Spitsbergen, Svalbard

Since the end of the Little Ice Age (LIA), widespread ice marginal recession in Svalbard has exposed extensive areas of glacier forelands that contain a diverse range of glacial landforms. Many of these landforms continue to evolve even after the ice margin retreated due to the presence of significant ice cores. The resulting associations of landforms and sediments are representative of the subpolar glacial landsystem and often display characteristics of glacial surges. Their currently dynamic state offers an ideal opportunity to study how changes in climatic conditions and geomorphological processes affect glacial process-form regimes.

The main objective of this study was to characterise and quantify the transition from glacial to postglacial conditions while evaluating the spatial and temporal evolution of glacial landsystems. Our focus was on the glaciers located near Petuniabukta in the central part of Spitsbergen Island. We mapped and quantified geomorphological and landscape changes across glacial forelands using a time series of remote sensing data combined with field verification. The dynamics of the proglacial areas of the studied glaciers—Hørbyebreen, Ebbabreen, Ragnarbreen, and Nordenskiöldbreen—illustrate the decay of a high-Arctic, polythermal (and potentially surging) glacial landsystem. By examining different types of surficial units as indicators of the dominant geomorphological processes, five main process-form regimes were identified: glacial-related, glaciofluvial, glaciolacustrine, downwasting, mass wasting processes, and stabilisation. Currently, direct glacial processes have a relatively low impact on landscape dynamics in the studied proglacial areas. Instead, most of the landscape transformations are related to:

• Mass wasting of lateral and frontal moraines, which results in large debris flows that repeatedly transform landforms and sediments (observed at Hørbyebreen, Ebbabreen, Ragnarbreen, and S Nordenskiöldbreen).
• Downwasting of dead ice buried under supraglacial debris, leading to the emergence of landforms associated with former englacial drainage and crevasse patterns (notably seen at Hørbyebreen).
• Glaciofluvial erosion and deposition, which effectively remove evidence of other processes and contribute to the formation of relatively flat inner outwash plains (at Hørbyebreen and Ebbabreen).
• The development of either localised (at Hørbyebreen, Ebbabreen, and S and N Nordenskiöldbreen) or large-scale (at Ragnarbreen) ponds and lakes, characterised by the rapid accumulation of fine-grained sediments. These ponds serve as local sediment traps.

From a spatio-temporal perspective, zones of actively transformed landscapes migrated through the glacial foreland as the ice margin retreated, resulting in an unstable topography that was partially ice-cored. Mass wasting processes initially altered these unstable landforms. Subsequently, depending on the degree of coupling between the glaciofluvial and moraine components, they could temporarily store sediments for varying periods, ranging from days to several decades, until they were fully depleted. The glacial-related regime has largely transitioned into one dominated by mass-wasting processes, characterised by the formation of large ice-cored latero-frontal moraines and transformed by glaciofluvial activities.