Suchergebnisse

15 páginas, 4 tablas, 5 figuras, 3 apéndices.-- Proyecto Carbochange ; Methods based on CO2 and chlorofluorocarbon (CFC) data are used to describe and evaluate the anthropogenic CO2 (Cant) concentrations, Cant specific inventories, and Cant storage rates in the Equatorial Atlantic Ocean. The Cant variability in the water masses is evaluated from the comparison of two hydrographic sections along 7.5°N carried out in 1993 and 2010. During both cruises, high Cant concentrations are detected in the upper layers, with values decreasing progressively towards the deep layers. Overall, the Cant concentrations increase from 1993 to 2010, with a large increment in the upper North Atlantic Deep Water layer of about 0.18 ± 0.03 μmol kg−1 y−1. In 2010, the Cant inventory along the whole section amounts to 58.9 ± 2.2 and 45.1 ± 2.0 mol m−2 using CO2 and CFC based methods, respectively, with most Cant accumulating in the western basin. Considering the time elapsed between the two cruises, Cant storage rates of 1.01 ± 0.18 and 0.75 ± 0.17 mol m−2 y−1 (CO2 and CFC based methods, respectively) are obtained. Below ∼1000 m, these rates follow the pace expected from a progressive increase of Cant at steady state; above ∼1000 m, Cant increases faster, mainly due to the retreat of the Antarctic Intermediate Waters ; This work was funded by the 7th Framework Programme (EU FP7 CARBOCHANGE, under grand agreement no. 264879) and by the Spanish Ministry of Economy and Competitiveness through Projects GHGMOC (CTM2009-07574-E), MOC2 (CTM2008-06438-C02-01/MAR) and ESCLAT (CTM2009-07405-E/MAR) and by the Deutsche Forschungsgemeinschaft (DFG) (M. Rhein, grant Rh25/36-1). FFP and AFR were supported by the Spanish Government and co-founded by the European Regional Development Fund (CTM2013-41048-P). ; Peer reviewed

6 páginas, 5 figuras, 1 tabla.-- Proyecto Carbochange.-- Open access ; Global ocean acidification is caused primarily by the ocean's uptake of CO2 as a consequence of increasing atmospheric CO2 levels. We present observations of the oceanic decrease in pH at the basin scale (50°S–36°N) for the Atlantic Ocean over two decades (1993–2013). Changes in pH associated with the uptake of anthropogenic CO2 (ΔpHCant) and with variations caused by biological activity and ocean circulation (ΔpHNat) are evaluated for different water masses. Output from an Institut Pierre Simon Laplace climate model is used to place the results into a longer-term perspective and to elucidate the mechanisms responsible for pH change. The largest decreases in pH (∆pH) were observed in central, mode, and intermediate waters, with a maximum ΔpH value in South Atlantic Central Waters of −0.042 ± 0.003. The ΔpH trended toward zero in deep and bottom waters. Observations and model results show that pH changes generally are dominated by the anthropogenic component, which accounts for rates between −0.0015 and −0.0020/y in the central waters. The anthropogenic and natural components are of the same order of magnitude and reinforce one another in mode and intermediate waters over the time period. Large negative ΔpHNat values observed in mode and intermediate waters are driven primarily by changes in CO2 content and are consistent with (i) a poleward shift of the formation region during the positive phase of the Southern Annular Mode in the South Atlantic and (ii) an increase in the rate of the water mass formation in the North Atlantic ; This research was supported by the Spanish Ministry of Sciences and Innovation and was cofunded by the European Regional Development Fund 2007–2012 (FEDER) through the Carbon Transport and Acidification Rates in the North Atlantic Project (CTM2010-17141/MAR), by the European Union Seventh Framework Programme CARBOCHANGE project under Grant Agreement 264879, and by the Office of Atmospheric and Oceanic Research of the NOAA ; Peer reviewed