The impact of climate variations on fluxes of oxygen in the Barents Sea

The effect of climate variability on the fluxes of oxygen to the top 150 m of the water column in the Atlantic Sector of the central Barents Sea have been investigated. A time series of hydrographic, phosphate, and oxygen data acquired at the Kola meridian transect were grouped into cold and warm years. A simple box model was applied to the daily change in mixed layer depth, phosphate and oxygen deficit in the top 150 m, and oxygen anomaly at the surface during typical cold and warm years. From this the following annual fluxes of oxygen were estimated: the flux due to biology, Fb; vertical mixing, Fv; and air–sea gas exchange, Fair.Fb was found to be 3.2 mol O2 m−2 yr−1 during cold and 2.3 mol O2 m−2 yr−1 during warm years, both of these estimates are certain within the –25% to +40% interval. Fv was estimated to be –0.7 mol O2 m−2 yr−1, in both cold and warm years. Finally, Fair was calculated to be 8.1 mol O2 m−2 yr−1 in cold years and 6.5 mol O2 m−2 yr−1 in warm years, using synoptic wind fields. Even if the absolute magnitude of Fair is uncertain due to the large errors associated with the calculation of the transfer velocities, the difference between cold and warm years is considered to be robust. This difference is a result of an increased meltwater pool capping the Atlantic Water during summer during cold years, thereby limiting the outgassing of oxygen in this season. The meltwater pool is also important for the development of the spring bloom, which is discussed. The realism of the flux estimates is strengthened by comparing the sum of Fb, Fv, and Fair, which is a measure of the net annual oxygen uptake in the region, with an estimate calculated using a mass balance approach.