Morphology and Development of Ice Patches in Northwest Territories, Canada

Permanent ice patches in the western Canadian Subarctic have been recently identified as sources of cryogenically preserved artifacts and biological specimens. The formation, composition, and constancy of these ice patches have yet to be studied. As part of the Northwest Territories (NWT) Ice Patch Study, ground-penetrating radar (GPR) and ice coring were used to examine the stratigraphy and internal structure of two ice patches. Results show the patches are composed of a core of distinct offset units, up to several metres thick, covered by a blanket of firn and snow. The interfaces between the units of ice are often demarcated by thin sections of frozen caribou dung and fine sediment. Radiocarbon dates of dung extracted from ice cores have revealed a long history for these perennial patches, up to 4400 years BP. Ice patch growth is discontinuous and occurs intermittently. Extensive time gaps exist between the units of ice, indicating that summers of catastrophic melt can interrupt extended periods of net accumulation. The results of this work not only display the character of ice patch development, but also indicate the significant role that ice patches can play in reconstructing the paleoenvironmental conditions of an area.