CO2 flux over young and snow-covered Arctic pack ice in winter and spring

• Published in: Biogeosciences
• Main Authors: Nomura, D., Granskog, M. A., Fransson, A., Chierici, M., Silyakova, A., Ohshima, K. I., Cohen, L., Delille, Bruno, Hudson, S. R., Dieckmann, G. S.
• Other Authors: FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus GmbH 2018
• Subjects: Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Arctic; Norway; Ocean acidification; Sea ice
• Online Access: https://orbi.uliege.be/handle/2268/232276; https://doi.org/10.5194/bg-15-3331-2018

peer reviewed Rare CO2 flux measurements from Arctic pack ice show that two types of ice contribute to the release of CO2 from the ice to the atmosphere during winter and spring: young, thin ice with a thin layer of snow and older (several weeks), thicker ice with thick snow cover. Young, thin sea ice is characterized by high salinity and high porosity, and snow-covered thick ice remains relatively warm (>-7.5 °C) due to the insulating snow cover despite air temperatures as low as -40 °C. Therefore, brine volume fractions of these two ice types are high enough to provide favorable conditions for gas exchange between sea ice and the atmosphere even in mid-winter. Although the potential CO2 flux from sea ice decreased due to the presence of the snow, the snow surface is still a CO2 source to the atmosphere for low snow density and thin snow conditions. We found that young sea ice that is formed in leads without snow cover produces CO2 fluxes an order of magnitude higher than those in snow-covered older ice (+1.0±0.6 mmolCm-2 day-1 for young ice and +0.2±0.2 mmolCm-2 day-1 for older ice). © Author(s) 2018. Japan Society for the Promotion of Science (15K16135, 24-4175); Research Council of Norway (KLIMAFORSK programme, grant 240639); N-ICE project; Grant for Joint Research Program of the Institute of Low Temperature Science, Hokkaido University; Flagship research program “Ocean acidification and ecosystem effects in Northern waters”