Observed trends of <i>p</i>CO<sub>2</sub> and air-sea CO2 fluxes in the North Atlantic Ocean

Abstract

Observed partial pressure of carbon dioxide ( p CO 2 ) and temperature data in surface and mixed layer seawater of the Northeast (49 o N, 16.5 o W) and Northwest (56.5 o N, 52.6 o W) Atlantic Ocean time series sites have been analyzed for seasonal variability and air-sea CO 2 fluxes. The NE PAP data showed an annual mean p CO 2 of 335.9 ± 89.6 m atm (2003), 286.7 ± 103.5 m atm (2004), and 335.9 ± 89.6 m atm (2005). The annual data for NW KI deployments indicated annual p CO 2 average of 336.6 ± 14.3 and 359.1 ± 25.3 m atm for 2004 and 2005 respectively. The oceanic p CO 2 distribution across the spatial gradients over a seasonal timescale is relatively homogeneous with marked seasonal variability. These data indicated consistently the undersaturation of oceanic surface water at the sites and thus a perennial carbon sink. Sea surface p CO 2 trend is marked by summertime minimum and wintertime maximum, while depicting anti-phase patterns with the observed temperature signals. Seasonal to annual CO 2 fluxes indicated a year-round CO 2 invasion of the NE and NW basins. Estimated net basin-scale CO 2 uptake fluxes of 2.96 ± 1.73 and 1.84 ± 1.3 mol m -2 CO 2 a -1 were obtained for NE PAP (2nd - 4th) and NW K1 deployments, respectively.