G04_P01

Exploiting radiocarbon to investigate the fate of permafrost organic matter supply to the Canadian Beaufort Sea

Bröder L^1,2, Lattaud J¹, Juhls B³, Eulenburg A³, Priest T⁴, Fritz M³, Matsuoka A⁵, Pellerin A⁶, Bossé-Demers T⁷, Rudbäck D⁸, O'Regan M⁸, Whalen D⁹, Haghipour N¹, Eglinton T¹, Overduin P³, Vonk J²

¹Swiss Federal Institute of Technology, Zürich, Switzerland, ²Vrije Universiteit, Amsterdam, The Netherlands, ³Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany, ⁴Max-Planck-Institute for Marine Microbiology, Bremen, Germany, ⁵University of New Hampshire, Durham, USA, ⁶Université du Québec à Rimouski, Rimouski, Canada, ⁷Université Laval, Québec City, Canada, ⁸Stockholm University, Stockholm, Sweden, ⁹Natural Resources Canada, Halifax, Canada

The Canadian Beaufort Sea receives large quantities of sediment, organic carbon and nutrients from rapid coastal erosion and permafrost thaw. In addition, the Mackenzie River, the largest North American Arctic river, discharges great amounts of freshwater, dissolved solids and suspended sediments to the Beaufort Sea. Current changes in these fluxes in response to the warming climate have uncertain consequences for the carbon budget on the shelf and in the deep ocean. To investigate the movement and transformation of organic matter along the land-ocean continuum, we collected water and surface sediment samples across the Beaufort Sea during fall 2021. Sampling locations span from shallow, coastal, sites with water depths ≤ 20 m, to shelf-break and deep-water settings on the continental slope (water depths of ≥1000 m). For this study, we use radiocarbon analyses of dissolved inorganic (DIC), dissolved organic (DOC) and particulate organic carbon (POC) for surface and bottom waters, as well as surface sediments, in order to compare, contrast and constrain the relative source contributions and ages of these different forms of carbon. Our results will help to better understand the fate of permafrost organic matter in the marine environment and to ultimately improve assessments of the Canadian Beaufort Sea shelf as a carbon source or sink and its potential trajectory with ongoing environmental changes.