Abstract
The article presents geomorphological analysis results for two outwash fans (sandurs), Elveflya and Nottingham, in the marginal zone of the Werenskiold Glacier in the south-west part of the Spitsbergen. The main goal of this study was to reconstruct the morphological evolution of these landforms and to identify the permafrost zone under their surface. For this purpose, age data of fossils were compiled and compared with newly exposed and dated fossil tundra in the layer glaciotectonically deformed by the forming glacier end moraine. Using this method, a time frame was identified for the glacier advance and for the simultaneous formation of the outwash plains. It was concluded that the Elveflya surface has been built-up with deposits since the Little Ice Age. Sediment deposition ended in the late 1960s, due to hydrographic changes and the redirection of all proglacial waters towards the Nottingham bay. A photointerpretation analysis based on two orthophotomaps and LANDSAT scenes allowed the identification of five microfans in Elveflya, of which two youngest fans have a twice shorter range than the other three. The sixth microfan is currently shaped by deposits washed from the slope of the end moraine. An additional focus was placed on a currently active sandur, which fills the Nottingham bay, in order to identify its growth rate. The average growth rate of this surface increased from 5700 m2·year−1 over the period of 1985–2000 to 24,900 m2·year−1 over the period of 2010–2017. Electromagnetic measurements carried out on the surfaces of the sandurs demonstrated that the electrical resistivity of the ground is high in the apex of the Elveflya fan (ρ ≥ 1 kΩ.m) and low in its toe (typically ρ < 200 Ω.m), as in the case of the Nottingham fan ground. In the interpretation advanced here, permafrost developed in the proximal part of the Elveflya sandur, which continues to be supplied by fresh groundwaters flowing from the glacier direction. Low electrical resistivity of the ground in the distal part of the outwash fan suggests the absence of ground ice in this zone, which is subjected to the intrusion of salty and comparatively warm seawater, reaching approximately 1 km inland under the surface of the low-elevated marine terrace. The identified zones additionally display different tendencies for vertical movements of the terrain surface, as identified with the Small Baseline Subset (SBAS) method. The proximal part of the Elveflya outwash fan is relatively stable, while its distal part lowers in the summer period by a maximum of 5 cm. The resulting morphological changes include linear cracks having lengths up to 580 m and an arc line consistent with the coastline.
Highlights
Despite the fact that the Svalbard permafrost has been researched for many years and is well-documented in borehole data [1,2], knowledge on the development of permafrost on morphologically active or recently formed surfaces remains limited
It can be assumed that the sediments filling the Svalbard bays and fjords in recent decades are subject to permanent freezing; this process is limited from the seaside by the thermal and chemical impact of sea water
The identified microfans evolved as a result of changes in the location of the main Kvisla channel, after the runoff of the Werenskiold Glacier proglacial waters was formed at the northern edge of its end moraine
Summary
Despite the fact that the Svalbard permafrost has been researched for many years and is well-documented in borehole data [1,2], knowledge on the development of permafrost on morphologically active or recently formed surfaces remains limited. It can be assumed that the sediments filling the Svalbard bays and fjords in recent decades are subject to permanent freezing; this process is limited from the seaside by the thermal and chemical impact of sea water. The main objective of this study was to attempt the identification of conditions stimulating the development of permafrost on the example of outwash fans in a coastal area, with a focus on their morphology and evolution stages. The ground temperature monitoring system in Svalbard provides, solid evidence of an increasing thickness of the permafrost active layer [22,23,24,25,26]
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