Dear Colleagues,

Is it in any way surprising that the Water journal accepted the idea to devote a Special Issue to the permafrost and active layer? Has permafrost always been connected to the occurrence of water? An unreflective answer may suggest that this is indeed the case. Permafrost means a constantly frozen medium.

However, we know that it is not so. Much of the permafrost is related to the presence of a cryotic state, i.e., a negative ground temperature with no freezing due to the freezing point dropping below 0 °C. This is mainly because of mineralization, increased pressure, clay content, or other factors. Unfrozen water may be a part of permafrost. In addition, such a situation occurs quite commonly on seacoasts and in glaciated areas—under glaciers.

What is the state of research on cryotic permafrost? By what methods can it be investigated? What proportion does it constitute in comparison to traditional, frozen permafrost, on a regional and global scale, and what types of threats does it cause? Those issues are almost unknown and constitute one of the basic challenges of permafrost studies.

The second problem is related to frozen water: ice. Here, too, the question of an interesting distinction arises: Can ice-free permafrost exist? What does the term dry permafrost mean? (Is the definition of 148 in Everdingen’s permafrost glossary correct?) Can ice be called dry water? How does it compare to other frozen mediums?

I know that such questions are not often asked today because there are other pressing research problems related to more practical issues: global warming, the related degradation of permafrost, an increase in the active layer, or the emission of methane and CO₂. Indeed, it is in this direction that the dominant amount of force and resources goes. These issues receive much more attention. However, the aforementioned issues are crucial for a correct understanding of the whole topic of permafrost, and especially its relationship with water in various forms. This research area seems to be rather neglected, but its broader development in this Special Issue may also benefit mainstream research on permafrost.

Dr. Wojciech Dobinski
Prof. Mauro Guglielmin
Dr. Dongliang Luo
Guest Editors

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• permafrost
• water
• dry permafrost
• cryotic state
• offshore permafrost
• ice