Air-Sea CO 2 fluxes in the Atlantic as measured during boreal spring and autumn

• Published in: Biogeosciences
• Main Authors: Padin, XA, Vazquez-Rodriguez, M, Castano, M, Velo, A, Alonso-Perez, F, Gago, J, Gilcoto, M, Alvarez, M, Pardo, PC, de la Paz, M, Rios, AF, Perez, FF
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus GmbH 2010
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Surface Processes; Drake Passage
• Online Access: https://doi.org/10.5194/bg-7-1587-2010; http://ecite.utas.edu.au/103047

A total of fourteen hydrographic cruises from 2000 to 2008were conducted during the spring and autumn seasons between Spain and theSouthern Ocean under the framework of the Spanish research project FICARAM.The underway measurements were processed and analysed to describe themeridional air-sea CO 2 fluxes ( F CO 2 ) in the covered sector of theAtlantic Ocean. The data has been grouped into different biogeochemicaloceanographic provinces based on thermohaline characteristics. The spatialand temporal distributions of F CO 2 followed expected distributions andannual trends reproducing the recent climatological Δ f CO 2 estimations with a mean difference of −3 18 μatm (Takahashi etal., 2009). The reduction in the CO 2 saturation along the meridionalFICARAM cruises represented an increase of 0.02 0.14 mol m −2 yr −1 in the ocean uptake of atmospheric CO 2 . The subtropicalwaters in both Hemispheres acted as a sink of atmospheric CO 2 duringthe successive spring seasons and as a source in autumn. The coarsereduction of the ocean uptake of atmospheric CO 2 observed in the NorthAtlantic Ocean was linked to conditions of negative phase of the NorthAtlantic Oscillation that prevailed during the FICARAM period. Surfacewaters in the North Equatorial Counter Current revealed a significantlong-term decrease of sea surface salinity of −0.16 0.01 yr −1 coinciding with a declination of −3.5 0.9 μatm yr −1 in theairsea disequilibrium of CO 2 fugacity and a rise of oceanic CO 2 uptake of −0.09 0.03 mol m −2 yr −1 . The largest CO 2 source was located in the equatorial upwelling system. These tropical watersthat reached emissions of 0.7 0.5 and 1.0 0.7 mol m −2 y −1 in spring and autumn, respectively, showed an interannual warmingof 0.11 0.03 C yr −1 and a wind speed decrease of −0.58 0.14 m s −1 yr −1 in spring cruises which suggest the weakening ofupwelling events associated with warm El Nio Southern Oscillationepisodes. Contrary the surface waters of the Patagonian Sea behaved as anintense sink of CO 2 in March and November. The oceanic waters of theconvergence of Falkland and Brazil Currents showed the strongest CO 2 absorption with a rate of −5.4 3.6 mol m −2 yr −1 in November.The Southern Oceans sampled in the Drake Passage behave as an average uptakerate of −1.1 0.9 mol m −2 yr −1 while the distal shelf of theLivingston Island acted as a slight source of CO 2 to the atmosphere.