Tracing terrestrial organic matter in two contrasting Arctic systems: A case study in the Mackenzie Trough in the Canadian Beaufort Sea and in Wijdefjorden in the Svalbard Archipelago

Abstract

The Arctic is warming twice as fast as other parts of the Earth by thawing permafrost and thus mobilizing the organic carbon (OC) stored in permafrost. With ongoing climate changes, inputs of terrestrial OC into the Arctic Ocean have been expected to increase through several pathways including river discharges, coastal erosions, and glacial discharges. In order to understand the Arctic carbon cycle, knowledge of OC dynamics with various regional characteristics is essential. The Mackenzie River, which flows into the Beaufort Sea, is the fourth-largest Arctic river in terms of freshwater discharge, but the first in terms of sediment discharge. Wijdefjorden is the longest fjord in Svalbard archipelago, located in the northern portion of the island of Spitsbergen, which supplies glacigenic terrestrial material through glacial discharges. In this study, two contrasting Arctic environments were investigated using surface sediments collected along Mackenzie Trough and Wijdefjorden during the expeditions of the R/V ARAON (ARA04C, ARA05C, and ARA08C in 2013, 2014, and 2017) and R/V Helmer Hanssen (HH17 in 2017), respectively. We analyzed the samples for bulk (e.g. Corg/Norg ratio, δ13Corg, and δ15Norg) and molecular (concentrations and δ13C of n-alkanes) parameters to assess sources of organic matter. In addition, we analyzed the radiocarbon content (Δ14C) to evaluate the contribution of fossil and non-fossil to the overall OC pool of OC. Our results will provide information on the contribution of organic carbon to the thawing of terrestrial permafrost in the two contrasting Arctic environmental systems.