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

Abstract

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.

Underway pCO2 Surveys Unravel CO2 Invasion of Lake Superior From Seasonal Variability

“…This research grappled with problems of bias in transect data due to overrepresentation of certain regions in space (the far western lake) and time (summer). Although these problems were partially addressed by regression analysis and separation of pelagic and riverine regimes, future work should consider other drivers of spatial and temporal heterogeneity, for example,: dissolved organic matter and chlorophyll measured by in‐situ instruments or remote sensing (e.g., Lohrenz et al., 2018; Sims et al., 2023). Expanded monitoring of p CO 2 and related chemical properties in the Laurentian Great Lakes provides a fruitful avenue for observation and modeling of CO 2 budgets in the world's largest surface freshwater resource.…”