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Underway pCO2 surveys unravel CO2 invasion of Lake Superior from seasonal variability
  • Daniel Edward Sandborn,
  • Elizabeth C. Minor
Daniel Edward Sandborn
University of Minnesota - Duluth

Corresponding Author:[email protected]

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Elizabeth C. Minor
University of Minnesota, Duluth
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This study observed seasonal trends and inferred drivers of CO2 biogeochemistry at the air-water interface of Lake Superior. Underway carbon dioxide partial pressure pCO2 was measured in surface water during 69 transects spanning ice free seasons of 2019-2022. These data comprise the first multiannual pCO2 time series in the Laurentian Great Lakes. Surface water pCO2 was closely tied to increasing atmospheric pCO2 by a 100 day CO2 equilibration timescale, while seasonal variability was controlled equally by thermal and biophysical drivers during the ice-free season. Comparison to previous modeling efforts indicates that Lake Superior surface pCO2 increased at a similar rate as the atmosphere over the preceding two decades. Spatial heterogeneity in CO2 dynamics was highlighted by a salinity-based delineation of “riverine” and “pelagic” regimes, each of which displayed a net CO2 influx over Julian days 100-300 on the order of 30 Gmol C. These findings refine previous estimates of Lake Superior C fluxes, support predictions of anthropogenic CO2 invasion, point to new observation strategies for large lakes, and highlight an urgent need for studies of changes to lacustrine C cycling.
30 Oct 2023Submitted to ESS Open Archive
03 Nov 2023Published in ESS Open Archive