Permafrost and groundwater interaction
Authors: Diak Magdalena , Borecka Marta , Böttcher Michael E. , Hong Wei-Li , Knies Jochen , Kotwicki Lech , Kuliński Karol , Lepland Aivo , Koziorowska-Makuch Katarzyna , Sen Arunima , von Ahn Catia M.E. , Winogradow Aleksandra , Szymczycha Beata 
Published: March 2022

&lt;p&gt;Permafrost is defined as perennially frozen ground (soil or rock and included ice and organic material) with a temperature near or below 0&amp;#176;C that remains for at least two consecutive years. Permafrost occurs mainly in high latitudes of the Southern and Northern Hemispheres, but significant area can also be found in the middle- and low-latitude regions. In these areas, the groundwater cycle is mainly controlled by the permafrost layer that may act as an aquiclude and hence block or retard the groundwater flow. However, rapid climate changes which are observed during the last decades, markedly contribute to permafrost degradation. New connections between permafrost and groundwater are expected to form during the permafrost thawing process. This will contribute to enhance permafrost and groundwater interaction and reinforce groundwater discharge. In general, groundwater discharge is a groundwater movement from the saturated ground to the surface water bodies or submarine groundwater inflow into the sea. Increased groundwater discharge may transport a significant amount of nutrients, metals, and gases to land and ocean waters and hence may change their physicochemical parameters. Unfortunately, due to the limited number of studies, understanding the significance of groundwater discharge in the Arctic regions is limited.&lt;/p&gt;&lt;p&gt;The study aims to provide a comprehensive review of the present literature data that contribute to better understanding interaction between permafrost and groundwater in the Arctic regions, which are particularly vulnerable to climate changes. This review is focused on permafrost thawing, groundwater discharge, and recharge processes and their implication on the environment. We attempt to answer the following questions: How does permafrost affect groundwater discharge and recharge? Does permafrost act as a hindrance for groundwater? How does progressive global warming and thereby permafrost thawing impact the groundwater discharge? How significant is groundwater discharge? How important is the transport of different solutes to the environment by groundwater discharge?&lt;/p&gt;&lt;p&gt;Based on the literature, we can conclude that the degradation of permafrost greatly influences hydrological systems in cold zones. Permafrost has a strong impact on fluid dynamics caused by negligible hydraulic conductivity. This relationship, beyond all physical, chemical, and biogeochemical responses, contributes to the formation of complex permafrost&amp;#8211;groundwater interactions. Permafrost degradation strongly affects the ecosystem through direct and indirect impacts on the transport and cycles of different compounds, elements, and ions. Moreover, all processes are dependent on topography, geomorphology, tectonics, and surface hydrology. Research conducted in other than Arctic permafrost areas also indicated that permafrost thawing is the cause of enhanced groundwater recharge and discharge rates, which resulted in deeper water tables and groundwater flow paths. However, comprehensible and systematic studies are still needed for global assessment also in terms of searching for interdependencies between different regions.&lt;/p&gt;&lt;p&gt;This belongs to Project No. 2019/34/H/ST10/00645 &quot;Submarine Groundwater Discharge in a Changing Arctic Region: Scale and Biogeochemical impact&quot;, which is supported by the Norwegian Financial Mechanism and Polish national Basic Research Program.&lt;/p&gt;