Release of dissolved organic carbon by coastal erosion in the southern Canadian Beaufort Sea - First results of a Master project

• Main Authors: Tanski, George, Lantuit, Hugues, Fritz, Michael, Strauss, Jens, Eulenburg, Antje, Rost, Tilman
• Format: Conference Object
• Language: unknown
• Published: 2012
• Subjects: Arctic; Yukon; Beaufort Sea; Ice; permafrost; wedge*
• Online Access: https://epic.awi.de/id/eprint/31880/; https://epic.awi.de/id/eprint/31880/1/Poster_Arctic_Net.pdf; https://hdl.handle.net/10013/epic.40633; https://hdl.handle.net/10013/epic.40633.d001

Arctic permafrost coasts make up around 34% of the world’s coastlines. These coasts are highly susceptible to erosion since they are mostly composed of ice-rich unconsolidated sediments. Current estimations of carbon released by coastal erosion largely focus on particulate organic carbon (POC). Dissolved organic carbon (DOC) contents in ground ice bodies are implicitly considered to be negligible. The few published numbers on DOC contents, recently measured on ice wedge samples, show nonetheless that concentrations are far from being negligible and that DOC in ground ice could play a substantial role in the Arctic carbon cycle. POC and DOC export from arctic rivers has been estimated in the past, reaching around 6 Tg/yr for POC and 33 Tg/yr for DOC, released mostly during the spring peak discharge. POC release from coastal erosion has also been quantified at around 8 Tg/yr, but DOC release from coastal erosion was never included. This is problematic, as ground ice is present nearly everywhere along the arctic coast. It can make up to 90% of the coastal bluffs in volume and can erode at rates up to 10 m/yr. In this study, we show the results of a case study focusing on the role of DOC in the nearshore carbon budget along the Yukon Coastal Plain. Several sites, in most cases natural exposures in retrogressive thaw slumps (RTS), were selected to be representative for sampling. In total, 42 samples of massive ground ice and ice wedges were obtained with a chainsaw and stored in a cold storage at -20°C before further processing. The samples were cut in a cold lab at -15°C in order to remove the melted and contaminated margins. The melted subsamples were then used for determining DOC contents and further hydrochemical (stable water isotopes, major anion and cations) and sedimentological parameters (particulate carbon content of sediment inclusions). In this presentation, we show the DOC contents from these samples, focusing on the relation with the genesis of the enclosing ground ice bodies. We then show that these results can be linked with known rates of coastal erosion and DOC discharge from RTS into the coastal zone and substantiate a comprehensive sediment and nutrient budget for the western part of the Canadian Beaufort Sea.