Coastal permafrost erosion, organic carbon and nutrient release to the arctic nearshore zone (COPER)
Arctic permafrost coasts, which account for 34% of the coasts of the Earth, are extremely vulnerable to climate change, because the frozen bluffs, upon contact with seawater, lose the cohesion provided by the permafrost matrix and are instantly washed away by incoming waves.
With warming in the Arctic expected to be roughly twice as high as the global mean, sea ice extent is expected to decline dramatically and induce favourable conditions for coastal erosion. The subsequent impacts include threats to infrastructure and changes to the nearshore food-web through the release of sediment and organic matter to the ocean. A comprehensive understanding of the processes at work at the local level is nonetheless still lacking and impeding any kind of prognosis on the trajectory of erosion rates. Process studies are therefore necessary to understand the response of Arctic coasts to environmental forcing and to better quantify the quantities of sediment and organic matter released by coastal erosion.
COPER is tacking this issue by conducting a scientific programme assessing the pace and nature of sediment and organic matter transfer in the Arctic coastal zone in a geographically and temporally integrated framework, by focusing on contemporary erosion in the southern Canadian Beaufort Sea.
At the study area, selected for representing different geomorphological and biogeophysical settings, transects perpendicular and parallel to the coastlines were established to:
- quantify and characterize the spatial variability of particulate and dissolved organic carbon and nutrient contents in permafrost sediments and ground ice as well their sediment characteristics through cross-shore sampling transects along the coastline;
- quantify the pace of arctic coastal erosion, the role of coastal thermokarst and of extreme events (storms) in the delivery of sediments to the sea through alongshore 3D surveys above and under sea level using air- and space-borne photogrammetry and multi-beam bathymetry; and
- assess the fate of released sediments in the nearshore zone and the deposition or export of organic matter in the nearshore environment through sediment cores taken in the nearshore zone and geophysical surveys.
The combination of all datasets enables the group to create comprehensive sediment and organic carbon and nutrient budgets, including both coastal erosion and coastal thermokarst, at an unequalled spatial and temporal resolution. This sediment budget will then be used to refine and publish circum-Arctic estimates of input of organic carbon, nitrogen and phosphorus to the nearshore zone, contributing datasets to international programs on coastal geochemical budgets.