CO 2 and CH 4 in sea ice from a subarctic fjord under influence of riverine input

• Published in: Biogeosciences
• Main Authors: O. Crabeck, B. Delille, D. Thomas, N.-X. Geilfus, S. Rysgaard, J.-L. Tison
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2014
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Greenland; Kapisillit; Sea ice; Subarctic
• Online Access: https://doi.org/10.5194/bg-11-6525-2014; https://doaj.org/article/23c393a71be2431995f81ee8f95e2434

We present the CH 4 concentration [CH 4 ], the partial pressure of CO 2 ( p CO 2 ) 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 δ 18 O 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 [CH 4 ] 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 p CO 2 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 CH 4 and CO 2 in sea ice, and we conclude that subarctic seawater can be a sink for atmospheric CO 2 , while being a net source of CH 4 .