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

Abstract

Abstract.Observations along the southwestern Atlantic WOCE A17 line made during the Dutch GEOTRACES-NL 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 ( C ant ). Application of the extended multilinear regression (eMLR) method shows that the 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 µmol kg −1 is found. South Atlantic Central Water (SACW) experienced the highest rate of increase in C ant , at 0.99 ± 0.14 µmol 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 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 µmol 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 CO 2 sink.

Diagnosing oceanic nutrient deficiency

“…Data on the distributions of the macronutrient elements N, P, Si [44,[62][63][64][65][66][67], the micronutrient elements Fe, Mn, Ni, Zn and Cd [64,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] and the non-nutrient element Al [67,85,86] were downloaded from the IDP2014 collection [20] and imported into a Matlab™ environment for analysis. For each sampling location and/or seawater volume/water mass, a ranking of the relative deficiencies of multiple nutrient elements was calculated by dividing observed dissolved concentrations by an assumed 'typical' stoichiometric ratio within newly formed organic (biological) material (figure 1) [11,18].…”

Variability of nutrients and carbon dioxide in the Antarctic Intermediate Water between 1990 and 2014

“…Salt et al (2015) reported rapid acidification of the AAIW in the southwest Atlantic. More to the south in the Weddell Gyre, nutrient concentrations significantly increased in the surface and bottom layers from 1996 to 2011 .…”

Long‐Term Trends in Phytoplankton Chlorophyll a and Size Structure in the Benguela Upwelling System

“…In addition to changes in upwelling frequency and intensity (Jarre et al, 2015;Lamont, García-Reyes, et al, 2018;Tim et al, 2015), shifts in the properties of upwelling source waters have also been noted in the South Atlantic (de Souza et al, 2018;Karstensen & Quadfasel, 2002;Salt et al, 2015;Venegas et al, 1998). While the impacts of such changes have not been described for the BUS, increased biomass and production in the California upwelling system have been related to elevated nitrate levels in source waters (Bograd et al, 2015;Rykaczewski and Dunne, 2010).…”