The Circumpolar Active Layer Monitoring (CALM) program is the primary program for long-term active-layer measurements (https://www2.gwu.edu/~calm/). This program aims to observe the response of the active layer and near-surface permafrost to climate change over multi-decadal time scales. Increases in active-layer thickness cause ground surface subsidence where sediments are ice-rich. Because this subsidence represents a loss of ground ice and a net export of latent heat, observations of surface subsidence are an important – but currently rare – component of monitoring that observed active-layer thickness and/or ground temperature change in boreholes (O’Neill et al., 2019; Gruber, 2020).
Though studies of subsidence of more than a decade (and longer) have been published recently, there is currently no organized repository to access data from various sources. In Canada, the Geological Survey maintains a network of thaw tubes that measure active layer thickness, thaw penetration, and ground surface subsidence, with records available since 1991 (e.g., Duchesne et al., 2015). Recently, ground surface subsidence in permafrost areas has been inferred using seasonal and multi-year datasets from in-situ observations (O’Neill et al., 2019; Gruber, 2020) as well as differential interferometric synthetic aperture radar. Integration of subsidence information using different sources would improve knowledge of landscape changes associated with permafrost thaw in ice-rich terrain.
References – Ground Subsidence and Active-Layer Thickness
Duchesne, C., S.L. Smith, M. Ednie, and P.P. Bonnaventure, 2015: Active Layer Variability and Change in the Mackenzie Valley, Northwest Territories. Proceedings of the 68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference, Canadian Geotechnical Society, 1-7.
Gruber, S., 2020: Ground Subsidence and Heave Over Permafrost: Hourly Time Series Reveal Interannual, Seasonal and Shorter-Term Movement Caused by Freezing, Thawing and Water Movement. The Cryosphere, 14(4), 1437-1447, doi.org/10.5194/tc-14-1437-2020.
O'Neill, H.B., S.L. Smith, and C. Duchesne, 2019: Long-term Permafrost Degradation and Thermokarst Subsidence in the Mackenzie Delta Area Indicated by Thaw Tube Measurements. American Society of Civil Engineers, 643–651, doi.org/10.1061/9780784482599.074.