Seasonal and interannual variability of the air–sea CO 2 flux in the Atlantic sector of the Barents Sea

Abstract

The seasonal and interannual variability of the air–sea CO 2 flux ( F) in the Atlantic sector of the Barents Sea have been investigated. Data for seawater fugacity of CO 2 ( fCO 2 sw) acquired during five cruises in the region were used to identify and validate an empirical procedure to compute fCO 2 sw from phosphate (PO 4), seawater temperature ( T), and salinity ( S). This procedure was then applied to time series data of T, S, and PO 4 collected in the Barents Sea Opening during the period 1990–1999, and the resulting fCO 2 sw estimates were combined with data for the atmospheric mole fraction of CO 2, sea level pressure, and wind speed to evaluate F. The results show that the Atlantic sector of the Barents Sea is an annual sink of atmospheric CO 2. The monthly mean uptake increases nearly monotonically from 0.101 mol C m − 2 in midwinter to 0.656 mol C m − 2 in midfall before it gradually decreases to the winter value. Interannual variability in the monthly mean flux was evaluated for the winter, summer, and fall seasons and was found to be ± 0.071 mol C m − 2 month − 1 . The variability is controlled mainly through combined variation of fCO 2 sw and wind speed. The annual mean uptake of atmospheric CO 2 in the region was estimated to 4.27 ± 0.68 mol C m − 2 .