Sedimentary Coastal Cliff Erosion in Greenland

Abstract

Climate change will increase the duration of annual sea‐ice‐free periods and shift precipitation patterns across the Arctic. Those factors are likely to increase erosion rates along its coasts. Large parts of the Arctic coast consist of hard rock. However, glacial, deltaic, and coastal sedimentary deposits occur in deglaciated areas and isostatic uplift following glaciations has created beach ridge plains and pocket beaches with coarse soft‐sediment cliffs. Hitherto, very little was known about the spatial distribution, erosion rates, and morphodynamics of soft sediment cliffs along the coast of Greenland. Here, we investigate a 3‐km sedimentary cliff section on the south coast of Qeqertarsuaq (Disko Island). We measured 2D cliff top erosion over 50 years between 1964 and 2014 as well as 3D cliff profile change over 2 years between 2019 and 2021. Morphometric indices of the gravel beach and cliff were calculated based on a series of cross‐shore elevation profiles. Wave run‐up at the beach fronting the cliff was modeled with XBeach‐G for a series of storm events under present day sea‐ice conditions and for a reduced sea‐ice scenario. Cliff top erosion rates varied along the cliff with maximum rates of 0.3 m y−1. The investigated coastal cliff erodes by two coupled processes: (a) precipitation‐driven surface runoff downslope the cliff and (b) wave‐driven erosion at the cliff toe. In a continuously warming climate, this study shows that erosion of soft coastal cliffs in Greenland thus can accelerate due to increased storminess and prolonging open water periods.

Measuring Cliff Top and Cliff Face Retreat Rates of a Coastal Drumlin Using Structure-from-Motion in Galway Bay, Ireland.

“…For PC alignment and change detection analysis, we used CloudCompare v2.13.alpha [64] following the protocols described by [11,13,63,66]. Since each PC is aligned to the same reference PC, specific GCPs were not needed for registration.…”

“…Previous studies have applied different research techniques to analyse cliff changes and erosion rates at numerous sites around the world. Among the most commonly reported methods are Structure-from-Motion (SfM) e.g., [11][12][13], analysis of historical maps and aerial photographs e.g., [13][14][15] and terrestrial Light Detection and Ranging (LiDAR) [16][17][18]. SfM is a photogrammetric approach that is now applied widely in geoscience disciplines, including geomorphology [12,19,20] and glaciology [21,22], to detect landform changes.…”

“…Depending on the data available, investigations into cliff retreat rates generally rely on one of three key methods. The first method estimates cliff retreat directly from changes in cliff top position, either from historical maps or orthophotos e.g., [13,14,26,27], while the second method employs erosional pins deployed near the base of the cliff to monitor changes in cliff face position e.g., [3,29]. More recently, the development of UAV and LiDAR technologies has provided a third method by providing high-resolution 3D modelling of cliff retreat from remotely sensed data [11,13,19].…”

“…The first method estimates cliff retreat directly from changes in cliff top position, either from historical maps or orthophotos e.g., [13,14,26,27], while the second method employs erosional pins deployed near the base of the cliff to monitor changes in cliff face position e.g., [3,29]. More recently, the development of UAV and LiDAR technologies has provided a third method by providing high-resolution 3D modelling of cliff retreat from remotely sensed data [11,13,19]. Recognising that methodology is largely dictated by data availability, prior research confirms that the choice of cliff top or cliff face estimates has the potential to influence results.…”

Exposure of Arctic coastal settlements to coastal erosion and permafrost warming

“…In Greenland, no settlements were estimated at risk from coastal erosion. Note that the majority of the Greenland coastline consists of solid rock and erosion is limited to unconsolidated cliffs (Luetzenburg et al, 2023). Due to ice recent ice loss, deltas shows a prograding trend in Greenland (Bendixen et al, 2017).…”