04 Aug 2022
 | 04 Aug 2022

High interannual surface pCO2 variability in the Southern Canadian Arctic Archipelago's Kitikmeot Sea

Richard Peter Sims, Mohamed Ahmed, Brian J. Butterworth, Patrick J. Duke, Stephen F. Gonski, Samantha F. Jones, Kristina A. Brown, Christopher J. Mundy, William J. Williams, and Brent G. T. Else

Abstract. Warming of the Arctic due to climate change means the Arctic Ocean is now ice-free for longer as sea ice melts earlier and refreezes later. It remains unclear how the extended ice-free period will impact carbon dioxide (CO2) fluxes due to scarcity of surface ocean CO2 measurements. Baseline measurements are urgently needed to understand how air−sea CO2 fluxes will spatially and temporally vary in a changing Arctic Ocean. It is uncertain whether the previous basin-wide surveys are representative of the many smaller bays and inlets that make up the Canadian Arctic Archipelago. By using a research vessel that is based in the remote Inuit community of Cambridge Bay (Ikaluqtuutiak, Nunavut), we have been able to reliably survey pCO2 shortly after ice melt and access previously unsampled bays and inlets in the nearby region. We present four years of consecutive summertime pCO2 measurements collected in the Kitikmeot Sea in the southern Canadian Arctic Archipelago. Overall, we found that this region is a sink for atmospheric CO2 in August (average of all calculated fluxes over the four cruises was -8.3 mmol m-2 d-1) but the magnitude of this sink varies substantially between years and locations (average calculated fluxes of 0.41, -7.70, -21.26 and -2.08 mmol m-2 d-1 during the 2016, 2017, 2018 and 2019 cruises respectively). Surface ocean pCO2 varied by up to 142 μatm between years; this highlights the importance of repeat observations in the Arctic as this high interannual variability would not have been captured by sparse and infrequent measurements. We find that the pCO2 value of the surface ocean at the time of ice melt is extremely important in constraining the magnitude of the air−sea flux throughout the ice-free season. Further constraining the flux in the Kitikmeot Sea will require a better understanding of how pCO2 changes outside of the summer season. Surface ocean pCO2 measurements made in the bays and inlets in the Kitikmeot Sea were ~20–40 μatm lower than in the main channels, and pCO2 measurements made close to ice breakup (i.e. within 2 weeks) were 50–100 μatm lower than measurements made >4 weeks after breakup. As basin-wide surveys of the CAA have focused on the deeper shipping channels and rarely measure close to the ice break-up date, we hypothesize that there may be an observational bias in previous studies, leading to an underestimate of the CO2 sink in the Canadian Arctic Archipelago. These high-resolution measurements constitute an important new baseline for gaining a better understanding of the role this region plays in the uptake of atmospheric CO2.

Richard Peter Sims 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-2022-710', Anonymous Referee #1, 11 Sep 2022
    • AC1: 'Reply on RC1', Richard Sims, 28 Oct 2022
  • RC2: 'Comment on egusphere-2022-710', Wiley Evans, 29 Sep 2022
    • AC2: 'Reply on RC2', Richard Sims, 28 Oct 2022

Richard Peter Sims et al.

Richard Peter Sims et al.


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Short summary
Using a small research vessel based out of Cambridge Bay in the Kitikmeot Sea (Canadian Arctic Archipelago), we were able to make measurements of surface ocean pCO2 shortly after sea ice breakup for four consecutive years. We compare our measurements to previous underway measurements and the two ongoing ocean carbon observatories in the region. We identify high inter annual variability and a potential bias in previous estimates due to lower pCO2 in bays and inlets.