permafrost

ikirouta Permanently frozen ground, or a specific layer thereof.
2003, Johannes C. Nonner, http://books.google.com/books?id=SQwrhRu4ZHwC Introduction to Hydrogeology, ISBN 9026518706, page 157,

Nevertheless, the water molecule is present, as ice, in a solid form in frozen soils or permafrosts, which cover large regions characterised by a polar climate.