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

• Published in: Biogeosciences Vol. 15; no. 11; pp. 3331 - 3343
• Main Authors: Nomura, Daiki, Granskog, Mats A, Fransson, Agneta, Chierici, Melissa, Silyakova, Anna, Ohshima, Kay I, Cohen, Lana, Delille, Bruno, Hudson, Stephen R, Dieckmann, Gerhard S
• Format: Journal Article Web Resource
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 05.06.2018; European Geosciences Union (EGU); Copernicus Publications
• Subjects: Air temperature; Atmosphere; Brines; Carbon dioxide; Carbon dioxide atmospheric concentrations; Carbon dioxide flux; Earth sciences & physical geography; Fluctuations; Fluxes; Gas exchange; Geofag: 450; Geosciences: 450; Ice; Ice cover; Ice formation; Matematikk og Naturvitenskap: 400; Mathematics and natural science: 400; Pack ice; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Polar environments; Porosity; Saline water; Sciences de la terre & géographie physique; Sea ice; Snow; Snow cover; Snow density; Spring; Temperature; VDP; Winter; Young ice; Arctic Ocean; Arctic region
• ISSN: 1726-4170; 1726-4189; 1726-4189
• DOI: 10.5194/bg-15-3331-2018

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 producesCO2 fluxes an order of magnitude higher than those in snow-covered older ice (+1.0 ± 0.6 mmolCm-2day-1 for young ice and +0.2 ± 0.2 mmolCm-2day-1 for older ice).