Paraglacial gullying of sediment‐mantled slopes: a case study of Colletthøgda, Kongsfjorden area, West Spitsbergen (Svalbard)

Abstract

International audienceThis paper evaluates the paraglacial evolution of a sediment-mantled slope in a polar maritime environment. The intensity of paraglacial processes is estimated through quantifi cation of erosion and dating of fi eld sectors with the help of photographic archives. Gully erosion has been estimated using morphometric parameters and by surveys of vegetation cover. The rapid melting of dead-ice cores controls gully formation. This leads to slope form modifi cation: gully profi le gradients are reduced from a mean of 35° to a mean ranging between 10° and 15°. Profi le evolution results from the collapse of glacier lateral moraine. All data (mean slope angle of individual gullies, frequency distribution of slope angles, fractional distance to the apex, gullying index, volume of debris mobilized, vertical erosion rate) tend to increase with increasing deglaciation age and the duration of paraglacial activity. Vegetation colonization is a response to stabilization of the ground surface and the drying up of the ground surface due to dead-ice melting. The full sequence of paraglacial slope adjustment (gully incision-stabilization) may occur rapidly at the study site, i.e. within two decades. Finally, a lateral morphogenic sequence is proposed showing the importance of paraglacial processes at the onset of the deglaciation

Conditions for feedbacks between geomorphic and vegetation dynamics on lateral moraine slopes: a biogeomorphic feedback window

“…The permanent decrease of geomorphic activity once Dryas octopetala cover reaches a value of 35% (Figure A) can be interpreted as density or biomass engineering threshold (Figure ; Balke et al , ). A similar vegetation cover threshold, delimiting active from inactive sediment‐mantled slopes, was also found on Svalbard (Mercier et al , ). Once this threshold is crossed, increasing D. octopetala cover amplifies the decrease of geomorphic activity by permanently inhibiting higher magnitude/frequency processes through its above‐ and below‐ground morphological and biomechanical traits (see earlier; Figure , plot 3).…”

Evolution of high-Arctic glacial landforms during deglaciation

“…In polar regions characterised by the presence of permafrost, rates of landsystem transformation are often expedited by the disintegration of buried ice (Fitzsimons, 1996;Bennett et al, 2000;Etienne et al, 2008;Oliva and Ruiz-Fernández, 2015). For example, Mercier et al (2009) reported that following deglaciation sediment mantled slopes undergo significant transformation, with the formation of gullies controlled by the ablation of buried ice. Conceptual pathways of landsystem evolution predict that upon complete deglaciation, icecored terrain will result in a 'hummocky' assemblage of landform (Boulton, 1972), although preservation of buried ice is permitted under an extensive sediment mantle.…”

Coupling patterns between para‐glacial and permafrost degradation responses in Antarctica

“…Some papers have examined para-glacial activity in polar and subpolar regions, mainly in the Arctic (e.g. Ballantyne and Benn, 1994;Mercier and Laffly, 2005;Mercier et al, 2009;Rachlewicz, 2010). However, there is a lack of studies focusing particularly on para-glacial processes in Antarctica.…”