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Volume 9, issue 4
The Cryosphere, 9, 1701-1713, 2015
https://doi.org/10.5194/tc-9-1701-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Interactions between climate change and the Cryosphere: SVALI,...

The Cryosphere, 9, 1701-1713, 2015
https://doi.org/10.5194/tc-9-1701-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 25 Aug 2015

Research article | 25 Aug 2015

Winter observations of CO2 exchange between sea ice and the atmosphere in a coastal fjord environment

J. Sievers1,3, L. L. Sørensen1,3, T. Papakyriakou5, B. Else7, M. K. Sejr2,3, D. Haubjerg Søgaard4,8, D. Barber5, and S. Rysgaard3,4,5,6 J. Sievers et al.
  • 1Department of Environmental Science, Aarhus University, 4000 Roskilde, Denmark
  • 2Department of Bioscience, Aarhus University, 8600 Silkeborg, Denmark
  • 3Arctic Research Centre, Aarhus University, 8000 Aarhus, Denmark
  • 4Greenland Climate Research Centre, c/o Greenland Institute of Natural Resources box 570, Nuuk, Greenland
  • 5Centre for Earth Observation Science, CHR Faculty of Environment Earth and Resources, University of Manitoba, 499 Wallace Building, Winnipeg, MB R3T 2N2, Canada
  • 6Department of Geological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
  • 7Department of Geography, University of Calgary, Calgary, AB T2N 1N4, Canada
  • 8Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Abstract. Eddy covariance observations of CO2 fluxes were conducted during March–April 2012 in a temporally sequential order for 8, 4 and 30 days, respectively, at three locations on fast sea ice and on newly formed polynya ice in a coastal fjord environment in northeast Greenland. CO2 fluxes at the sites characterized by fast sea ice (ICEI and DNB) were found to increasingly reflect periods of strong outgassing in accordance with the progression of springtime warming and the occurrence of strong wind events: FCO2ICE1 = 1.73 ± 5 mmol m−2 day−1 and FCO2DNB = 8.64 ± 39.64 mmol m−2 day−1, while CO2 fluxes at the polynya site (POLYI) were found to generally reflect uptake FCO2POLY1 = −9.97 ± 19.8 mmol m−2 day−1. Values given are the mean and standard deviation, and negative/positive values indicate uptake/outgassing, respectively. A diurnal correlation analysis supports a significant connection between site energetics and CO2 fluxes linked to a number of possible thermally driven processes, which are thought to change the pCO2 gradient at the snow–ice interface. The relative influence of these processes on atmospheric exchanges likely depends on the thickness of the ice. Specifically, the study indicates a predominant influence of brine volume expansion/contraction, brine dissolution/concentration and calcium carbonate formation/dissolution at sites characterized by a thick sea-ice cover, such that surface warming leads to an uptake of CO2 and vice versa, while convective overturning within the sea-ice brines dominate at sites characterized by comparatively thin sea-ice cover, such that nighttime surface cooling leads to an uptake of CO2 to the extent permitted by simultaneous formation of superimposed ice in the lower snow column.

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