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

• Published in: Biogeosciences
• Main Authors: Crabeck, O., Delille, B., Thomas, D., Geilfus, N.-X., Rysgaard, S., Tison, J.-L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2014
• Subjects: article; Verlagsveröffentlichung; Greenland; Kapisillit; Sea ice; Subarctic
• Online Access: https://doi.org/10.5194/bg-11-6525-2014; https://noa.gwlb.de/receive/cop_mods_00018119; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00018074/bg-11-6525-2014.pdf; https://bg.copernicus.org/articles/11/6525/2014/bg-11-6525-2014.pdf

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.