Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard

Abstract

Abstract. Cold glacier beds, i.e., where the ice is frozen to its base, are widespread in polar regions. Common theories state that stable permafrost should exist under glacier beds on shorter timescales, varying from years to decades. Presently, only a few direct measurements of both subglacial permafrost and the processes influencing its thermal regime exist. Here, we present subglacial permafrost and active layer measurements obtained from within the basal drainage systems of two cold-based glaciers on Svalbard during the summer melt season. Temperature observations were obtained from subglacial sediment that was accessed through the drainage systems of the two glaciers in the previous winters. The temperature records cover the periods from spring to autumn in 2016 and 2019 at the glaciers Larsbreen and Tellbreen in central Svalbard. The ground temperature below Larsbreen indicates colder ground conditions, whereas the temperatures of the Tellbreen drainage system show considerably warmer conditions, close to the freezing point. We suggest the latter is due to the presence of liquid water all year round inside the Tellbreen drainage system. Both drainage systems investigated show an increase in subglacial sediment temperatures after the disappearance of snow bridges and the subsequent connection to surface meltwater supply at the start of the summer melt season. Temperature records show influence of sudden summer water supply events, when heavy melt and rain left their signatures on the thermal regime and the erosion of the glacier bed. Observed vertical erosion can reach up to 0.9 m d−1 at the base of basal drainage channels during summer. We also show that the thermal regime under the subglacial drainage systems is not stable during summer but experiences several freeze–thaw cycles driven by weather events. Our results show the direct importance of heavy melt events and rain on the thermal regime of subglacial permafrost and the erosion of the glacier bed in the vicinity of subglacial drainage channels. Increased precipitation and surface melt, as expected for future climate, will therefore likely lead to increased degradation of subglacial permafrost, as well as higher subglacial erosion of available sediment around the preferential hydrological paths. This in turn might have significant impacts on proglacial and fjord ecosystems due to increased sediment and nutrient input.

The thermal impact of tourism on a Svalbard glacier cave (Short Communication)

“…In comparison to the temperature records from glacier cave systems not used for touristic purposes (Alexander et al 2020), clear and frequent temperature perturbations are present. These can be linked to the heat input from cave visitors in all cases where information about visits is available.…”

The role of dead ice in transforming glacier forelands under the rapid climate warming of recent decades, OscarIILand, Svalbard

“…Permafrost also affects areas of modern glaciers' forelands. There it is associated not only with its aggradation in areas freed from ice but also partly with persistent subglacial permafrost (Alexander et al, 2020;Etzelmüller & Hagen, 2005;Sollid & Sørbel, 1994). The trend of constantly increasing average annual temperatures in Spitsbergen in recent decades, including in the research area (Kejna & Sobota, 2019, 2021, is causing a systematic deepening of the active layer (AL) thickness (ALT) of permafrost (Sobota et al, 2018).…”

MOLISENS: a modular MObile LIdar SENsor System to exploit the potential of automotive lidar for geoscientific applications

“…Ice volume changes in caves are common throughout the year and the inter-seasonal comparison of ice dynamics can indicate a change in the hydro-climatic regime of the glacier (Perşoiu and Lauritzen, 2017). Previous work on cold glacier caves in the study area involved geomorphological mapping and seasonal temperature monitoring (Alexander et al, 2020;Guðmundsdóttir, 2011), but detailed 3D measurements of a glacier cave system are typically not available.…”