Articles | Volume 11, issue 23
Biogeosciences, 11, 6525–6538, 2014
Biogeosciences, 11, 6525–6538, 2014

Research article 01 Dec 2014

Research article | 01 Dec 2014

CO2 and CH4 in sea ice from a subarctic fjord under influence of riverine input

O. Crabeck1, B. Delille2, D. Thomas3,4, N.-X. Geilfus6, S. Rysgaard1,5,6, and J.-L. Tison7 O. Crabeck et al.
  • 1Center for Earth Observation Science, Department of Geological Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
  • 2Unité d'Océanographie Chimique, Université de Liège, Liège, 4000, Belgium
  • 3School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, UK
  • 4Marine Research Centre, Finnish Environment Institute, Helsinki, Finland
  • 5Greenland Climate Research Centre, c/o Greenland Institute of Natural Resources, 3900 Nuuk, Greenland
  • 6Arctic Research Centre, Aarhus University, 8000 Aarhus, Denmark
  • 7Laboratoire de Glaciologie, D.S.T.E., Université Libre de Bruxelles, Brussels, 1050, Belgium

Abstract. We present the CH4 concentration [CH4], the partial pressure of CO2 (pCO2) and the total gas content in bulk sea ice from subarctic, land-fast sea ice in the Kapisillit fjord, Greenland. Fjord systems are characterized by freshwater runoff and riverine input and based on δ18O data, we show that > 30% of the surface water originated from periodic river input during ice growth. This resulted in fresher sea-ice layers with higher gas content than is typical from marine sea ice. The bulk ice [CH4] ranged from 1.8 to 12.1 nmol L−1, which corresponds to a partial pressure ranging from 3 to 28 ppmv. This is markedly higher than the average atmospheric methane content of 1.9 ppmv. Evidently most of the trapped methane within the ice was contained inside bubbles, and only a minor portion was dissolved in the brines. The bulk ice pCO2 ranged from 60 to 330 ppmv indicating that sea ice at temperatures above −4 °C is undersaturated compared to the atmosphere (390 ppmv). This study adds to the few existing studies of CH4 and CO2 in sea ice, and we conclude that subarctic seawater can be a sink for atmospheric CO2, while being a net source of CH4.

Final-revised paper