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


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Judith.Hauck [ at ] awi.de

Abstract

Antarctic Intermediate Water (AAIW) formation constitutes an important mechanism for the export of macronutrients out of the Southern Ocean that fuels primary production in low latitudes. We used quality-controlled gridded data from five hydrographic cruises between 1990 and 2014 to examine decadal variability in nutrients and dissolved inorganic carbon (DIC) in the AAIW (neutral density range 27 < γ n <  27.4) along the Prime Meridian. Significant positive trends were found in DIC (0.70 ± 0.4 μmol kg− 1 year− 1) and nitrate (0.08 ± 0.06 μ mol kg− 1 year− 1) along with decreasing trends in temperature (− 0.015 ± 0.01∘C year− 1) and salinity (− 0.003 ± 0.002 year− 1) in the AAIW. Accompanying this is an increase in apparent oxygen utilization (AOU, 0.16 ± 0.07 μ mol kg− 1 year− 1). We estimated that 75% of the DIC change has an anthropogenic origin. The remainder of the trends support a scenario of a strengthening of the upper-ocean overturning circulation in the Atlantic sector of the Southern Ocean in response to the positive trend in the Southern Annular Mode. A decrease in net primary productivity (more nutrients unutilized) in the source waters of the AAIW could have contributed as well but cannot fully explain all observed changes.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
46651
DOI 10.1007/s10236-018-1131-2

Cite as
Panassa, E. , Santana-Casiano, J. M. , González Dávila, M. , Hoppema, M. , Van Heuven, S. M. A. C. , Völker, C. , Wolf-Gladrow, D. and Hauck, J. (2018): Variability of nutrients and carbon dioxide in the Antarctic Intermediate Water between 1990 and 2014 , Ocean Dynamics, 68 (3), pp. 295-308 . doi: 10.1007/s10236-018-1131-2


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