Climate change is amplified in arctic and boreal regions, with one consequence of higher average temperatures and less precipitation in the summer months being longer wildfire seasons, severity, frequency and areal extent. This increases the release of carbon into the atmosphere as greenhouse gases and aerosols, amplifying climate change even further. Black carbon (BC), resulting from the incomplete combustion of biomass and fossil fuels, is produced on land, but a fraction of BC is exported by rivers to the oceans as both dissolved BC (DBC) and particulate BC, where it may be sequestered for millennia. Its fate along the river-to-ocean continuum determines the role of BC as a carbon sink. It is thus important to understand sources, transformations and fate of BC in the arctic given the increased prevalence of fires in this climatically vulnerable region. Here, we examine the sources, characteristics and fate of riverine DBC carried by the Mackenzie River to the adjacent Beaufort Sea. DBC concentrations in ocean water and corresponding d¹⁴C values were determined for samples collected on two cruises covering the outflow of the Mackenzie River and its mixing with the Beaufort Sea in 2021 and 2022 covering the outflow of the Mackenzie River. We use the concentration and ¹⁴C characteristics of specific DBC marker compounds to resolve the sources, transport pathways and fate of DBC in the Mackenzie River/Arctic Ocean system.

Primary Presenter: Linn Speidel, ETH Zürich (lspeidel@ethz.ch)

Authors:

Linn Speidel, ETH Zurich  (lspeidel@ethz.ch)

Lisa Bröder, ETH Zurich  (lisa.broeder@erdw.ethz.ch)

Julie Lattaud, ETH Zurich  (julie.lattaud@erdw.ethz.ch)

Negar Haghipour, ETH Zurich  (negar.haghipour@erdw.ethz.ch)

Timothy Eglinton, ETH Zurich  (timothy.eglinton@erdw.ethz.ch)

Alysha Coppola, ETH Zurich  (acoppola@ethz.ch)