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

• Published in: Ocean Dynamics
• Main Authors: Panassa, E., Santana-Casiano, J.M., González-Dávila, M., Hoppema, M., van Heuven, S.M.A.C., Völker, C., Wolf-Gladrow, D., Hauck, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://www.vliz.be/imisdocs/publications/54/311754.pdf

Antarctic Intermediate Water (AAIW) formation constitutes an important mechanism for the export of macronutrients outof the Southern Ocean that fuels primary production in low latitudes. We used quality-controlled gridded data from fivehydrographic cruises between 1990 and 2014 to examine decadal variability in nutrients and dissolved inorganic carbon(DIC) in the AAIW (neutral density range 27 < γn < 27.4) along the Prime Meridian. Significant positive trends werefound in DIC (0.70 } 0.4 μmol kg−1 year−1) and nitrate (0.08 } 0.06 μmol kg−1 year−1) along with decreasing trends intemperature (−0.015}0.01 ◦C year−1) and salinity (−0.003}0.002 year−1) in the AAIW. Accompanying this is an increasein apparent oxygen utilization (AOU, 0.16 } 0.07 μmol kg−1 year−1). We estimated that 75% of the DIC change has ananthropogenic origin. The remainder of the trends support a scenario of a strengthening of the upper-ocean overturningcirculation in the Atlantic sector of the Southern Ocean in response to the positive trend in the Southern Annular Mode. Adecrease in net primary productivity (more nutrients unutilized) in the source waters of the AAIW could have contributed aswell but cannot fully explain all observed changes.