Air–sea flux of CO₂ in arctic coastal waters influenced by glacial melt water and sea ice

Annual air–sea exchange of CO₂ inYoung Sound,NEGreenlandwas estimated using pCO₂ surface-water measurements during summer (2006–2009) and during an ice-covered winter 2008. All surface pCO₂ values were below atmospheric levels indicating an uptake of atmospheric CO₂. During sea ice formation, dissolved inorganic carbon (DIC) content is reduced causing sea ice to be under saturated in CO₂. Approximately 1% of the DIC forced out of growing sea ice was released into the atmosphere while the remaining 99% was exported to the underlying water column. Sea ice covered the fjord 9 months a year and thereby efficiently blocked air–sea CO₂ exchange. During sea ice melt, dissolution of CaCO₃ combined with primary production and strong stratification of the water column acted to lower surface-water pCO₂ levels in the fjord. Also, a large input of glacial melt water containing geochemically reactive carbonate minerals may contribute to the low surface-water pCO₂ levels. The average annual uptake of atmospheric CO₂ was estimated at 2.7 mol CO₂ m⁻² yr⁻¹ or 32 g C m⁻² yr⁻¹ for the study area, which is lower than estimates from the Greenland Sea. Variability in duration of sea ice cover caused significant year-to-year variation in annual gas exchange.