06 Feb 2023
 | 06 Feb 2023

The marine methane cycle in the Canadian Arctic Archipelago during summer

Alessandra D'Angelo, Cynthia Garcia-Eidell, Zak Kerrigan, Jacob Strock, Frances Crable, Nikolas VanKeersbilck, Humair Raziuddin, Theressa Ewa, Samira Umar, Andrew L. King, Miquel Gonzelez-Meler, and Brice Loose

Abstract. In the Arctic Ocean region, methane concentrations are higher than the global average; high concentrations of dissolved CH4 are detectable especially across many subarctic and Arctic continental shelf margins. Yet the Arctic Ocean appears to emit only minimal methane fluxes to the atmosphere across the air-sea interface, suggesting water column oxidation of methane may be an important process. Here we paired thermohaline, chemical, and biological data collected during the Northwest Passage Project transit through the Canadian Arctic Archipelago (CAA) waters in the Summer of 2019, with in-situ and in-vitro methane data. Our results showed high meltwater (meteoric water + sea ice melt) throughout the Western CAA and Croker Bay in the East, and these surface meltwaters showed methane excess. The meteoric waters showed a strong correlation with chlorophyll-α fluorescence (r=0.63), as well as a correlation between dissolved [CH4] and chlorophyll-α fluorescence (r=0.74). Methane oxidation rate constants were highest in Wellington Channel and Croker Bay surface waters (av. 0.01±0 d-1), characterized by meltwaters and Pacific-origin waters. The average oxidation rates in meteoric and Pacific waters were respectively 24.4 % and 12.6 % higher than the entire survey average. Moreover, Pacific and meteoric waters hosted microbial taxa of Pacific-origin that are associated with methane oxidation, Oleispira (γ-proteobacteria), and Aurantivirga (Flavobacteria). The deeper layers were characterized by low methane concentrations and low methane oxidation rate constants (av. 0.004±0.002 d-1). Sea ice covered much of the Western CAA, in the same region with high sea ice meltwater concentrations. These waters also hosted higher average methane oxidation rates (av. 0.007±0.002 d-1). To the east, open coastal water coincided with methane enrichment, but low chlorophyll fluorescence and weak methane oxidation. These results suggest that methane production in ice-associated Arctic blooms may be quickly oxidized by microbes that are also found in these waters, associated with seasonal biology.

Alessandra D'Angelo et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-74', Anonymous Referee #1, 28 Feb 2023
    • AC1: 'Reply on RC1', Alessandra D'Angelo, 18 Mar 2023
  • RC2: 'Comment on egusphere-2023-74', Anonymous Referee #2, 07 Mar 2023
    • AC2: 'Reply on RC2', Alessandra D'Angelo, 18 Mar 2023
  • RC3: 'Comment on egusphere-2023-74', Anonymous Referee #3, 08 Mar 2023
    • AC3: 'Reply on RC3', Alessandra D'Angelo, 18 Mar 2023
  • RC4: 'Comment on egusphere-2023-74', Anonymous Referee #4, 17 Mar 2023
    • AC4: 'Reply on RC4', Alessandra D'Angelo, 18 Mar 2023

Alessandra D'Angelo et al.

Alessandra D'Angelo et al.


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Short summary
In this paper, we seek to further elucidate the methane budget in the Northwest Passage, and detect its main association with the environmental features and the biogenic control within the water column and the sea ice. Collectively, we can divide the entire study area into: (a) sea ice, with methane excess; (b) meltwaters, characterized by methane oxidations in oversaturated waters; (c) Pacific waters, with high methane oxidation rates; (d) Atlantic regime, mostly abiotic for methane.