Spatial variability of modern carbon burial in the Canadian Beaufort Sea 

Arctic continental shelves play a key role in the biogeochemical cycle by transporting and storing organic matter (OM) originating from permafrost, yet the spatial variability of sedimentation and OM accumulation remains poorly constrained. On the Canadian Beaufort Shelf, existing estimates of organic carbon (OC) storage are based on Holocene sedimentation rates derived from seismic data, while direct observations are rare and geographically limited (n=5). Here, we present new sedimentological and radiometric data from 17 sites spanning the Beaufort Shelf and continental slope. Measurements of total organic carbon, grain and dry density, as well as radionuclide profiles (210Pb, 226Ra, 137Cs), are used to estimate sediment accumulation, mass accumulation, and OC burial over the last ~150 years. Sedimentation rates derived from the Constant Flux-Constant Sedimentation (CF:CS) model are compared with those from a Bayesian 210Pb age modeling framework (rplum). CF:CS yields higher sedimentation rates (mean = 0.23 ± 0.15 cm yr-1) than rplum (mean = 0.17 ± 0.07 cm yr-1). Estimated OC burial rates range from 3.6 to 51.4 g m-2 yr-1, with the highest values found near the Mackenzie Delta and in the Kugmallit Trough. For shelf areas between 20-100 m water depth, our new data suggest average OC burial rates (24.4 g m-2 yr-1) that are three times higher than previously reported. Combined with shallow-shelf estimates, total carbon burial is revised to 1.44 Tg C yr-1, 75% higher than earlier estimates.