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Permafrost-affected soils cover about 40–45 % of Canada. Theenvironment in such areas, especially those located within the discontinuouspermafrost zone, has been impacted more than any other by recorded climaticchanges. A number of changes, such as surface subsidence and the degradationof frost mounds due to permafrost thawing, have already been observed at manylocations.  We surveyed three frost mounds (lithalsas) in the subarctic, close toUmiujaq in northern Quebec, using high-precision differential globalpositioning system (d-GPS) technology during field visits in 2009, 2010 and2011, thus obtaining detailed information on their responses to the freezingand thawing that occur during the course of the annual temperature cycle.Seasonal pulsations were detected in the frost mounds, and these responseswere shown to vary with their state of degradation and the land cover. Themost degraded lithalsa showed a maximum amplitude of vertical movement(either up or down) between winter (freezing) and summer (thawing) of0.19 ± 0.09 m over the study period, while for the least degradedlithalsa this figure was far greater (1.24 ± 0.47 m). Records fromareas with little or no vegetation showed far less average vertical movementover the study period (0.17 ± 0.03 m) than those with prostrate shrubs(0.56 ± 0.02 m), suggesting an influence from the land cover.  A differential interferometric synthetic aperture radar (D-InSAR) analysiswas also completed over the lithalsas using selected TerraSAR-X imagesacquired from April to October 2009 and from March to October 2010, with arepeat cycle of 11 days. Interferograms with baselines shorter than 200 mwere computed revealing a generally very low interferometric coherence,restricting the quantification of vertical movements of the lithalsas.Vertical surface movements of the order of a few centimeters were recordedin the vicinity of Umiujaq

Vertical movements of frost mounds in subarctic permafrost regions analyzed using geodetic survey and satellite interferometry