The imprint of physical mixing on surface water N2O and CH4 concentrations in the eastern Canadian Arctic Ocean

  • Rebecca L. Rust Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada; and Department of Earth and Environmental Science, University of Rochester, Rochester, NY, USA https://orcid.org/0000-0002-1978-3354
  • Paul G. Myers Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada https://orcid.org/0000-0003-4514-2654
  • Philippe D. Tortell Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada; and Department of Botany, University of British Columbia, Vancouver, BC, Canada https://orcid.org/0000-0003-0212-2151
DOI: https://doi.org/10.33265/polar.v45.13047
Keywords: Climate change, greenhouse gases, polynyas

Abstract

We present high-frequency surface water measurements and discrete depth profiles of nitrous oxide (N2O) and methane (CH4) across the eastern Canadian Arctic Ocean, during early autumn 2023. Over the entire study region, surface water N2O concentrations were close to atmospheric saturation (96–111%), while surface water CH4 was generally supersaturated (between 197 and 445%). The highest surface water saturation of both gases was observed in northern Foxe Basin, a region of intense mixing over a shallow continental shelf. To examine the influence of vertical mixing on N2O and CH4 distributions, we coupled our field observations with output from a numerical model of the Arctic Ocean. This analysis revealed that gas supersaturation was associated with regions of enhanced vertical mixing, as indicated by elevated vertical eddy diffusivity (Kz) and weakly stratified seawater density profiles. Our results also suggest a significant imprint of lateral advection on the surface water distribution of N2O and CH4. Air–sea fluxes of N2O and CH4 during our early autumn sampling period exceeded previous summertime estimates from the eastern Canadian Arctic by up to an order of magnitude. On the basis of this observation, and an analysis of seasonal variability in model-derived mixing intensity, we argue that summertime studies may not adequately resolve high air–sea fluxes during early autumn associated with reduced stratification, low sea-ice cover, elevated mixing and wind-driven gas exchange. Our work highlights potential variability in surface gas concentrations associated with enhanced water column stratification under warming conditions across the Arctic Ocean and prompts the need for further measurements over a greater part of the seasonal cycle.

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Published
2026-10-01
How to Cite
Rust , R. L., Myers , P., & Tortell , P. (2026). The imprint of physical mixing on surface water N2O and CH4 concentrations in the eastern Canadian Arctic Ocean. Polar Research, 45. https://doi.org/10.33265/polar.v45.13047
Issue
Vol. 45 (2026)
Section
Research Articles
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