| Summary: | International audience Polar regions are very sensitive to climate variability. Glacial environments, such as Spitsbergen, respond drastically to climate warming by the disintegration of ice masses, release of huge amounts of free water and rapid evolution of terrestrial landforms. Paraglacial studies have shown that sediment yield decreases with time following a relaxation curve. The study examines the effects of scaling on rythms of deglaciation and sediment fluxes in a small catchment. The study site was located on the Kongsfjorden area, northwest Spistbergen, Svalbard, in the front of Baron and Conway glaciers (79°N, 12°20'E). The area consists of a patchwork of glacial and fluvioglacial deposits that are reworked or built by paraglacial processes, and was investigated for field geomorphological mapping. To reconstruct the kinematics of deglaciation since the end of the Little Ice Age, several photographics sources (from 1907 to 2004) have been collected and analysed. Sedimentological analyses were made of samples collected in the field. Grain-size deposits were analysed using wet- and dry- mechanical- sieving techniques to isolate the gravel and sand fractions. Fine fraction was measured using a Coulter LS230 laser granulometer. This study provides several insights into the relationship between temporal scales, climatic variability and geomorphological responses. Glacier response to climate variations is non-linear and not immediate and depends of the catchment size and induced differential geomorphological responses. In a source-to-sink-fluxes and sediment budget perspective, this example illustrates the different stages of the paraglacial sediment cascade. It appears that the paraglacial sequence, known as a morphogenic crisis, could be affected by internal small threshold events, which are able to mobilize large quantities of sediment. It means that, at small scale, the curve profile is more irregular than suggested by large-scale models. Les régions polaires sont très sensibles à la variabilité ...
|
|---|