Multi‐decadal trends in the advection and mixing of natural carbon in the Southern Ocean

Multi‐decadal trends in the advection, mixing, and air‐sea flux of natural carbon dioxide (CO2) in the Southern Ocean are investigated using output from a hindcast simulation of a non‐eddy‐resolving ocean model. Particular emphasis is placed on the model's improved eddy‐induced advection parameterization. From 1958 to 2007, the model predicts a significant increase in the outgassing of natural CO2 from the Southern Ocean, congruent with a positive trend in the wind speed over this period. The natural CO2 flux trend is largely driven by enhanced Eulerian‐mean advection and diapycnal mixing of dissolved inorganic carbon (DIC) into the Southern Ocean surface. The natural CO2 flux trend would be larger, if not for an increase in the eddy‐induced advection of DIC out of the Southern Ocean surface, caused by the multi‐decadal increase in the model's eddy‐induced advection coefficient.

[1]  S. Bates,et al.  The CCSM4 Ocean Component , 2012 .

[2]  Peter R. Gent,et al.  Response to Increasing Southern Hemisphere Winds in CCSM4 , 2011 .

[3]  Peter R. Gent,et al.  The effects of the eddy-induced advection coefficient in a coarse-resolution coupled climate model , 2011 .

[4]  N. Lovenduski,et al.  The future evolution of the Southern Ocean CO 2 sink , 2009 .

[5]  K. Lindsay,et al.  Mechanisms governing interannual variability in upper-ocean inorganic carbon system and air–sea CO2 fluxes: Physical climate and atmospheric dust , 2009 .

[6]  S. Rintoul,et al.  The response of the Antarctic Circumpolar Current to recent climate change , 2008 .

[7]  S. Doney,et al.  Toward a mechanistic understanding of the decadal trends in the Southern Ocean carbon sink , 2008 .

[8]  M. Meredith,et al.  Eddy Heat Flux in the Southern Ocean: Response to Variable Wind Forcing , 2008 .

[9]  R. Dickinson,et al.  Couplings between changes in the climate system and biogeochemistry , 2007 .

[10]  Casper Labuschagne,et al.  Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change , 2007, Science.

[11]  Keith Lindsay,et al.  Upper ocean ecosystem dynamics and iron cycling in a global three‐dimensional model , 2004 .

[12]  J. Marshall,et al.  Residual-Mean Solutions for the Antarctic Circumpolar Current and Its Associated Overturning Circulation , 2003 .

[13]  P. Gent,et al.  Isopycnal mixing in ocean circulation models , 1990 .

[14]  M. Redi.  Oceanic Isopycnal Mixing by Coordinate Rotation , 1982 .