3.4 Permafrost data

Lead Authors: Stephan Gruber (Carleton University), Brendan O’Neill (NRCan/GSC), Ashley Rudy (NTGS)

Contributors: Feresteh Ghiami-Shomami (Carleton University), Silvie Harder (CCCS/ECCC), Ryan Hennessey (CCCS/ECCC), Brian Horton (Yukon Research Centre), Galina Jonat (Carleton University), Hannah Macdonell (Carleton University)

3.4.1 Introduction
Permafrost is part of the climate system and is defined as ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least two consecutive years.
3.4.2 Ground Temperature
While permafrost is defined via ground temperature, interest in permafrost is based on the phenomena of thaw, i.e., ice loss in the ground. When thaw occurs, ground temperature often stagnates just below 0°C due to latent heat transfer.
3.4.3 Subsurface Ice Content
Ground ice is a key component of permafrost landscapes. The formation and melt of subsurface ice can alter topography, damage infrastructure, and modify hydrological processes.
3.4.4 Permafrost extent
Permafrost extent (Obu, 2021) expresses the areal proportion of ground underlain by permafrost. It usually assumes that no temporal change occurs (equilibrium).
3.4.5 Landform Inventories
Permafrost landform inventories provide information on subsurface processes through their surface expression as landforms and are a reflection of the glacial, periglacial, and climatic history of a region.
3.4.6 Ground Subsidence and Active-Layer Thickness
Datasets exist on the thickness of the active layer, the layer above permafrost that freezes and thaws annually, and subsidence of the ground surface due to ice-rich permafrost thaw.