Permafrost Base Degradation: Characteristics and Unknown Thread With Specific Example From Hornsund, Svalbard

Abstract

Permafrost degradation is one of the most pressing issues in the modern cryosphere related to climate change. Most attention is paid to the degradation of the top of the active permafrost associated with contemporary climate. This is the most popular issue because in the subsurface part of it there is usually the greatest accumulation of ground ice in direct relation to the changes taking place. The melting of ground ice is the cause of the greatest changes related to subsidence and other mass-wasting processes. The degradation of the subsurface permafrost layer is also responsible for the increased emission of CO2 and methane. However, this is not a fully comprehensive look at the issue of permafrost degradation, because depending on its thickness, changes in its thermal properties may occur more or less intensively throughout its entire profile, also reaching the base of permafrost. These changes can degrade permafrost throughout its profile. The article presents the basic principles of permafrost degradation in its overall approach. Both the melting of the ground ice and the thermal degradation of permafrost, as manifested in an increase in its temperature in part or all of the permafrost profile, are discussed. However, special attention is paid to the degradation characteristics from the permafrost base. In the case of moderately thick and warm permafrost in the zone of its sporadic and discontinuous occurrence, this type of degradation may particularly contribute to its disappearance, and surficial consequences of such degradation may be more serious than we expect on the basis of available research and data now. A special case of such degradation is the permafrost located in the coastal zone in the vicinity of the Hornsund Spitsbergen, where a multidirectional thermal impact is noted, also causing similar degradation of permafrost: from the top, side and bottom. Especially the degradation of permafrost from the permafrost base upwards is an entirely new issue in considering the evolution of permafrost due to climate change. Due to the difficulties in its detection, this process may contribute to the threats that are difficult to estimate in the areas of discontinuous and sporadic permafrost.

The summer heatwave in 2022 and its role in changing permafrost and periglacial conditions at a historic mountain pass in the Eastern Alps (Hochtor, Hohe Tauern Range, Austria)

“…The interpreted downward degradation of permafrost at the Hochtor site develops commonly when the maximum depth of seasonal thawing exceeds the maximum depth of seasonal freezing, resulting in the formation of the supra‐permafrost talik. This talik disconnects the permafrost from the seasonal frost layer, further enhancing permafrost degradation 65 . Based on our observed development of the GT and the resistivity values, it can be assumed that at least the near‐surface permafrost at the Hochtor will soon be history.…”

Paraglacial transformation and ice‐dammed lake dynamics in a high Arctic glacier foreland, Gåsbreen, Svalbard

“…The rest of the land is controlled by the presence of permafrost, which is present in ice free terrain in a continuous form in deglaciated mountain ranges and valleys (Gilbert et al, 2018; Humlum et al, 2003). The coastal permafrost is strongly controlled by sea water intrusion and exposure to wave impacts disturbing its shape and spatial distribution along the shores (Dobiński & Kasprzak, 2022; Kasprzak, 2020; Kasprzak et al, 2017).…”

“…The last few decades of sustained warming of the Arctic region are predominantly reflected in a strong surface air temperature rise and extensive decline of the sea‐ice cover (e.g., Barry, 2017; Sumata et al, 2022; Thoman et al, 2020). Warming of the Arctic climate entailed also changes in terrestrial environments such as an increase of ground temperatures and degradation of permafrost (e.g., Dobiński & Kasprzak, 2022; Karjalainen et al, 2020; Smith et al, 2022), and/or rapid retreat of glaciers (e.g., Cook et al, 2019; Hugonnet et al, 2021; Małecki, 2022; Sasgen et al, 2022). Among subregions of the Arctic, exceptional climate warming was characteristic of the Barents Sea region with Svalbard Archipelago at its heart (Isaksen et al, 2022).…”

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

“…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). However, this process is not even over a larger area and is largely dependent on local factors such as morphology, sun exposure, duration of snow cover, and lithology and its related water content (Araźny & Grze s, 2000;Dobi nski & Kasprzak, 2022;Etzelmüller et al, 2011;Migała, 1991;Rachlewicz & Szczuci nski, 2008). This last factor is discussed because an increase in AL humidity increases the latent heat of fusion for a thaw, which inhibits the deepening of the AL (Zhang et al, 2005), while an increase in water content is associated with increased thermal conductivity and AL deepening (Kwon et al, 2016).…”