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

[摘要] Observations along the southwestern Atlantic WOCE A17 line made during theDutch GEOTRACES-NL programme (2010–2011) were compared with historical data from1994 to quantify the changes in the anthropogenic component of the totalpool of dissolved inorganic carbon (ΔC_ant). Application of theextended multi-linear regression (eMLR) method shows that the ΔC_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 SubantarcticZone (SAZ), where a maximum increase of 37 μmol kg⁻¹ is found.South Atlantic Central Water (SACW) experienced the highest rate of increasein C_ant, at 0.99 ± 0.14 μmol kg⁻¹ yr⁻¹, resulting ina maximum rate of decrease in pH of 0.0016 yr⁻¹. The highest rates ofacidification relative to ΔC_ant, however, were found inSubantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). Thelow buffering capacity of SAMW and AAIW combined with their relatively highrates of C_ant, increase of 0.53 ± 0.11and 0.36 ± 0.06 μmol kg⁻¹ yr⁻¹, respectively, has lead torapid acidification in the SAZ, and will continue to do so whilstsimultaneously reducing the chemical buffering capacity of this significantCO₂ sink.

[学科分类] 地球化学与岩石