Impacts of vertical mixing and ice-melt on N2O and CH4 concentrations in the Canadian Arctic Ocean

Abstract

The sources and sinks of methane (CH4) and nitrous oxide (N2O) in the Arctic Ocean are subject to significant uncertainty, due to a combination of high spatial and temporal variability, and limited observations over relevant scales. To address this, an underway ship-board system was developed to simultaneously and continuously measure surface water CH4 and N2O concentrations in the Canadian Arctic Ocean, providing high-resolution data over a range of hydrographic regimes. Across our survey region during late summer, 2021, CH4 and N2O saturation ranged from 94% to 231% and 96%–120%, respectively. Localized CH4 and N2O maxima were observed along the cruise track, including high concentrations over the continental shelf of eastern Baffin Island, and in some waters influenced by sea ice cover or recent glacier retreat. We use our high-resolution data to examine the relationship between N2O and CH4 concentrations and a variety of oceanographic variables, demonstrating both positive correlations with salinity, which reflects the likely influence of vertical mixing, and negative correlations with salinity, indicative of ice-melt and freshwater inputs. These results build upon previous discrete CH4 and N2O observations in the Canadian Arctic, providing new information on the fine-scale distribution of these gases, and the potential underlying biogeochemical factors driving their variability. Results from our work have implications for understanding the biogeochemical cycling of Arctic Ocean CH4 and N2O under a rapidly warming climate.