Quantifying rates of soil deflation with Structure-from-Motion photogrammetry in west Greenland

Aeolian processes are important drivers of geomorphic change in cold regions. Because these processes often occur at slow timescales over large areas, it can be difficult to quantify rates using traditional field methods. In the Kangerlussuaq region of Greenland, strong katabatic winds have shaped distinct erosional landforms, or deflation patches, that appear to expand across the landscape. The modern erosion rate along the active margins, or scarps, of these deflation patches is unknown. We use Structure-from-Motion (SfM) photogrammetry to quantify the geomorphic change of ten deflation patches between 2014 and 2016. During the two-year study period, significant positive and negative change occurred at all sites, suggesting that deflation patches are active landforms and that geomorphic change is highly heterogeneous and localized. We observed significant change primarily along the scarps, while little to no change occurred in the center of the patches. Along the scarps, the mean negative change ranged from −0.7 to −2.5 cm, and erosion dominated in eight out of the ten deflation patches. The modern erosion rate appears to be lower than the century-scale rate of 2.5 cm yr −1 estimated from prior work using lichenometry, potentially because of the episodic nature of scarp retreat. Longer-term monitoring using these methods will help quantify the geomorphic response of this landscape to a rapidly changing regional climate.