Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean

• Published in: Biogeosciences
• Main Authors: Salt, L.A., van Heuven, S.M.A.C., Claus, M.E., Jones, E.M., de Baar, H.J.W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: ANTHROPOGENIC CO2; SOUTHERN-OCEAN; NORTH-ATLANTIC; INDIAN-OCEAN; ATMOSPHERIC CO2; CARBONIC-ACID; MASSES; INCREASE; SEA; DISTRIBUTIONS; Antarctic; Indian; Southern Ocean; Antarc*; Carbonic acid; North Atlantic
• Online Access: https://hdl.handle.net/11370/1529f3ff-73f6-4d03-afa6-32fe3b958785; https://research.rug.nl/en/publications/1529f3ff-73f6-4d03-afa6-32fe3b958785; https://doi.org/10.5194/bg-12-1387-2015; https://pure.rug.nl/ws/files/50273724/Rapid_acidification_of_mode_and_intermediate_waters.pdf

Observations along the southwestern Atlantic WOCE A17 line made during the Dutch GEOTRACESNL programme (2010-2011) were compared with historical data from 1994 to quantify the changes in the anthropogenic component of the total pool of dissolved inorganic carbon (Delta C-ant). Application of the extended multilinear regression (eMLR) method shows that the Delta C-ant from 1994 to 2011 has largely remained confined to the upper 1000 dbar. The greatest changes occur in the upper 200 dbar in the Subantarctic Zone (SAZ), where a maximum increase of 37 mu mol kg(-1) is found. South Atlantic Central Water (SACW) experienced the highest rate of increase in C-ant, at 0.99 +/- 0.14 mu mol kg(-1) yr(-1), resulting in a maximum rate of decrease in pH of 0.0016 yr(-1). The highest rates of acidification relative to Delta C-ant, however, were found in Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). The low buffering capacity of SAMW and AAIW combined with their relatively high rates of C-ant increase of 0.53 +/- 0.11 and 0.36 +/- 0.06 mu mol kg(-1) yr(-1), respectively, has lead to rapid acidification in the SAZ, and will continue to do so whilst simultaneously reducing the chemical buffering capacity of this significant CO2 sink.