Ocean Circulation and Climate: Chapter 30. The Marine Carbon Cycle and Ocean Carbon Inventories (International Geophysics) by Körtzinger Arne & Bates Nicholas R. & Tanhua Toste

Author:Körtzinger, Arne & Bates, Nicholas R. & Tanhua, Toste [Körtzinger, Arne]
Language: eng
Format: epub
Publisher: Elsevier Science
Published: 2013-10-21T16:00:00+00:00

Pacific and Indian Ocean Rates of Anthropogenic CO2 Uptake

Contemporary net carbon transports exhibit a strong convergence of carbon in the equatorial Pacific. In the South Pacific, natural and anthropogenic CO 2 fluxes enhance each other, resulting in large northward fluxes ( Gruber et al., 2009 ). In the North Pacific Ocean, the situation is complex but the anthropogenic component is generally small and both compensate for and enhance natural carbon fluxes. A sizeable fraction of anthropogenic CO 2 leaves the equatorial region via the ITF toward the Indian Ocean as mentioned above.

4.3 Atlantic Ocean

The Atlantic Ocean shows a rather symmetric CO2 source/sink pattern of contemporary atmospheric CO2 with sizeable ocean CO2 sinks in the 14°–50° latitude band of the northern (− 0.20 Pg C yr− 1 , Takahashi et al., 2009 ) and southern hemisphere (− 0.21 Pg C yr− 1 , Takahashi et al., 2009 ). Both ocean CO2 sink regions are dominated by the latitude band 35°–50° since the subtropical regions (14°–35°) are neutral or weak sources. The tropical band (14°N–14°S) acts as a source of CO2 to the atmosphere (0.10 Pg C yr− 1 , Takahashi et al., 2009 ) comparable in size to the Indian Ocean but far weaker than estimated for the Pacific Ocean. The Southern Ocean sector of the Atlantic Ocean behaves very much like the Southern Ocean of the other two basins, the region north of 50°N represents a significant sink despite its comparatively small area (− 0.27 Pg C yr− 1 , Takahashi et al., 2009 ) due to very high CO2 flux rates. Overall, the Atlantic Ocean constitutes an oceanic sink for CO2 (− 0.58 Pg C yr− 1 , Takahashi et al., 2009 ) that represents 41% of the global ocean CO2 sink, which is far in excess of its areal fraction (23%). It should also be noted that the Atlantic Ocean was a net sink of CO2 in preindustrial times (e.g., Gruber et al., 2009 ).

For the entire Atlantic Ocean basin (North and South Atlantic, excluding marginal seas such as the Mediterranean Sea) published estimates of C ant inventories range from 40 to 55 Pg C ( Table 30.6 ; Sabine et al., 2004a ; Touratier and Goyet, 2004 ; Vázquez-Rodríguez et al., 2009 ; Velo et al., 2010 ), representing approximately 35–40% of the global ocean estimates (e.g., Sabine et al., 2004a ; Khatiwala et al., 2013 ). In the North Atlantic Ocean, the anthropogenic CO 2 inventories range from 20 to 36 Pg C ( Table 30.6 ; Gruber et al., 1996 ; Gruber, 1998 ; Lee et al., 2003 ; Sabine et al., 2004a ; Steinfeldt et al., 2009 ), or about 50–60% of the total Atlantic inventory, with variability in the estimates imparted in part from the different latitudinal zones used. Estimates for the South Atlantic Ocean are more limited and range from 16.5 to 18.5 Pg C ( Table 30.6 ; Gruber, 1998 ; Lee et al., 2003 ; Sabine et al., 2004a ).

Table 30.

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