Observed acidification trends in North Atlantic water masses

• Published in: Biogeosciences
• Main Authors: Vázquez Rodríguez, Marcos, Pérez, Fiz F., Velo, A., Ríos, Aida F., Mercier, Herlé
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union 2012
• Subjects: Iceland; Labrador Sea; North Atlantic; Ocean acidification; Subarctic
• Online Access: http://hdl.handle.net/10261/64124; https://doi.org/10.5194/bg-9-5217-2012

14 páginas, 4 figuras, 3 tablas.-- Proyecto Carbochange The lack of observational pH data has made it difficult to assess recent rates of ocean acidification, particularly in the high latitudes. Here we present a time series that spans over 27 yr (1981–2008) of high-quality carbon system measurements in the North Atlantic, which comprises fourteen cruises and covers the important water mass formation areas of the Irminger and Iceland Basins. We provide direct quantification of acidification rates in upper and intermediate North Atlantic waters. The highest rates were associated with surface waters and with Labrador Sea Water (LSW). The Subarctic Intermediate and Subpolar Mode Waters (SAIW and SPMW) showed acidification rates of −0.0019±0.0001 and −0.0012±0.0002 yr−1, respectively. The deep convection activity in the North Atlantic Subpolar Gyre injects surface waters loaded with anthropogenic CO2 into lower layers, provoking the remarkable acidification rate observed for LSW in the Iceland Basin (−0.0016±0.0002 yr−1). An extrapolation of the observed linear acidification trends suggests that the pH of LSW could drop 0.45 units with respect to pre-industrial levels by the time atmospheric CO2 concentrations reach 775 ppm. Under circulation conditions and evolution of CO2 emission rates similar to those of the last three decades, by the time atmospheric CO2 reaches 550 ppm, an aragonite undersaturation state could be reached in the cLSW of the Iceland Basin, earlier than surface SPMW. The research leading to these results was supported by the EU FP7 project CARBOCHANGE “Changes in carbon uptake and emissions by oceans in a changing climate”, which received funding from the European Commission’s Seventh Framework Programme under grant agreement no. 264879; by the Spanish Ministry of Science and Innovation and co-funded by Fondo Eurpeo de Desarrollo Regional 2007–2012 (FEDER) through the CATARINA Project (CTM2010-17141). The OVIDE research project was co-funded by the IFREMER, CNRS/INSU and LEFE. H.M. was ...