Seawater Intrusion on the Arctic Coast (Svalbard): The Concept of Onshore-Permafrost Wedge

Abstract

Numerous hydrogeological studies on the coastal zone describe the intrusion of sea water inland, salting underground aquifers. The phenomenon is commonly observed in the coasts outside polar areas. However, the impact of sea water has so far not been an object of detailed investigation in a periglacial environment devoid of subsea permafrost. Geophysical measurements at the west coast of the Wedel-Jarlsberg Land in Svalbard indicate that the border between the unfrozen seabed and the frozen ground onshore is not delimited by the shoreline. A zone of coastal unfrozen ground is located under a thin layer of permafrost reaching toward the sea. This state was observed with the use of electrical resistivity tomography under rocky headlands and capes, uplifted marine terraces located at the foot of mountain massifs and valley mouths as well as in the marginal zone of the Werenskiold Glacier. This short article presents the results of such a measurement, supplemented with electromagnetic detection. The measurements are unique in that they were conducted not only on the land surface, but also at the floor of the sea bay during the low water spring tide. The author proposes name structures detected in the coastal zone as a “permafrost wedge”, extending an identification of the permafrost base between the coast and the glaciers of Svalbard. However, in the absence of boreholes that would allow determining the thermal state of the ground in the study sites, the concept is based only on the interpretation of the geophysical imaging. Therefore, further discussion is required on whether the identified contrasts in electrical resistivity indeed result from thermal differences between the rocks or if they only indicate the cryotic state of the ground (saline cryopeg) within the range of seawater intrusion.

Saltwater Intrusion Intensifies Coastal Permafrost Thaw

“…Without solute exclusion, ice‐saturated permafrost formed under the saltwater boundary, and the saltwater wedge was flushed out. In contrast, with solute exclusion a permafrost wedge formed at the coast, creating initial ice‐saturated permafrost distributions similar to those derived from recent geophysical measurements of such a system (Kasprzak, 2020). Additionally, the saltwater wedge was present and hypersaline conditions (i.e., salinity greater than seawater) were established as observed in high‐latitude marine settings (Harris et al., 2017; Spirina et al., 2017).…”

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

“…This situation was visualized using electrical resistivity tomography (ERT) in 2012 on the west coast of Spitsbergen (Kasprzak et al, 2017) and similarly confirmed by geophysical methods also in other locations (Strzelecki et al, 2017;Kasprzak 2020;Kasprzak et al, 2020;Pedrazas et al, 2020). The presence of sea intrusion leads to the formation of a horizontal "permafrost wedge" subjected to changes under influence of air temperature from above and sea water temperature from below, as shown in Figure 5.…”

Onshore Thermokarst Primes Subsea Permafrost Degradation

“…Lateral seawater intrusion beneath a thin permafrost base was interpreted by electrical resistivity surveys several decameters inland in Svalbard (Kasprzak et al., 2017), leading to the concept of an onshore‐permafrost wedge (Kasprzak, 2020). Due to seawater intrusion, this concept explains that the thickness of onshore permafrost increases with distance from the coastline.…”