A talik is a layer of year-round unfrozen ground that lies in permafrost areas. In regions of continuous permafrost, taliks often occur underneath shallow thermokarst lakes and rivers, where the deep water does not freeze in winter, and thus the soil underneath will not freeze either. Sometimes closed, open and through talik are distinguished. These terms refer to whether the talik is completely surrounded by permafrost, is open to the top (e.g. a thermokarst lake), or open to both top and unfrozen layers beneath the permafrost, respectively.
Due to climate fluctuation or change, some permafrost regions may develop an unfrozen layer between the seasonally thawing/freezing active layer and the permafrost. The layer is called supra-permafrost (above the permafrost) talik; it is different from traditional taliks, which are usually associated with water bodies, in that supra-permafrost talik occurs because the ground that thawed in the summer does not completely refreeze in the winter. Calculations show that climate warming would induce supra-permafrost taliks in intermediately cold regions (in very cold regions, warming simply induces a deeper summer thaw without forming the talik layer; while in warm, shallow permafrost regions, permafrost quickly disappears). This type of taliks has recently been observed in Russia. With time and continued increase in air temperature or snow depth, this talik layer will become thicker and thicker and the deep permafrost layer would eventually disappear. Findings from a scientific study suggest occurrence of open taliks within areas of fault zones and those influenced by large rivers.
- D Nicolsky and N Shakhova (25 March 2010), Modeling sub-sea permafrost in the East Siberian Arctic Shelf: the Dmitry Laptev Strait, IOP Science