Sahar Palangi - PhD student of water engineering, Department of Science and water engineering, Faculty of agriculture, Bu Ali Sina University, Hamedan, Iran
Hamid Zare-Abyaneh - Assistant of professor, Department of Science and water engineering, Faculty of agriculture, Bu Ali Sina University, Hamedan, Iran

Permafrost is perennially frozen ground remaining at or below 0°C for at least two consecutive years. Any location with annual average air temperatures below freezing can potentially form permafrost. Most of the current permafrost formed during or since the last ice age and can extend down to depths of more than 700 meters. Arctic and alpine air temperatures are expected to increase at roughly twice the global rate and climate projections indicate substantial loss of permafrost by 2100. A global temperature increase of 3°C means a 6°C increase in the Arctic, resulting in anywhere between 30 to 85% loss of near-surface permafrost. Such widespread permafrost degradation will permanently change local hydrology, increasing the frequency of fire and erosion disturbances. This paper reviews Permafrost as a natural phenomenon which under the influence of global warming and climate change has become a threat.

Permafrost , perennially frozen ground, climate change, global warming