Efficiency of small scale carbon mitigation by patch iron fertilization

Biogeosciences Discussions 01/2009; 7(11). DOI: 10.5194/bg-7-3593-2010
Source: DOAJ

ABSTRACT While nutrient depletion scenarios have long shown that the high-latitude High Nutrient Low Chlorophyll (HNLC) regions are the most effective for sequestering atmospheric carbon dioxide, recent simulations with prognostic biogeochemical models have suggested that only a fraction of the potential drawdown can be realized. We use a global ocean biogeochemical general circulation model developed at GFDL and Princeton to examine this and related issues. We fertilize two patches in the North and Equatorial Pacific, and two additional patches in the Southern Ocean HNLC region north of the biogeochemical divide and in the Ross Sea south of the biogeochemical divide. We obtain by far the greatest response to iron fertilization at the Ross Sea site. Here the CO2 remains sequestered on century time-scales and the efficiency of fertilization remains almost constant no matter how frequently iron is applied as long as it is confined to the growing season. The second most efficient site is in the Southern Ocean. Here the biological response to iron fertilization is comparable to the Ross Sea, but the enhanced biological uptake of CO2 is more spread out in the vertical and thus less effective at leading to removal of CO2 from the atmosphere. The North Pacific site has lower initial nutrients and thus a lower efficiency. Fertilization of the Equatorial Pacific leads to an expansion of the suboxic zone and a striking increase in denitrification that causes a sharp reduction in overall surface biological export production and CO2 uptake. The impacts on the oxygen distribution and surface biological export are less prominent at other sites, but nevertheless still a source of concern. The century time scale retention of iron in these models greatly increases the long-term biological response to iron addition as compared with models in which the added iron is rapidly scavenged from the ocean.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Artificial ocean iron fertilization (OIF) enhances phytoplankton productivity and is being explored as a means of sequestering anthropogenic carbon within the deep ocean. To be considered successful, carbon should be exported from the surface ocean and isolated from the atmosphere for an extended period (e.g. the IPCCÕs standard 100-year time-horizon). This study assesses the impact of deep circulation on carbon sequestered by OIF in the Southern Ocean, a high-nutrient-low-chlorophyll region known to be iron-stressed. A Lagrangian particle-tracking approach is employed to analyze water mass trajectories over a 100-year simulation. By the end of the experiment, for a sequestration depth of 1000 m, 66% of the carbon had been re-exposed to the atmosphere, taking an average of 37.8 years. Upwelling occurs predominately within the Antarctic Circumpolar Current due to Ekman suction and topography. These results emphasize that successful OIF requires consideration of the role of circulation as well asbiogeochemistry.
    Geophysical Research Letters. 03/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Using results from an earth system model, the distribution of partial pressure of () in surface seawater over the East China Sea is investigated. In this area shows minimum along the edge of the continental break along the path of the Taiwan-Tsushima Current System. Apparently modelled chlorophyll is also great along the current but the maximum of the chlorophyll and the minimum of do not coincide suggesting that the primary production is not the main cause of the minimum. As we move toward the Yellow Sea from the Kuroshio area the temperature decreases so that the becomes smaller. If we move further toward the Yellow Sea beyond the Taiwan-Tsushima Current System, alkalinity starts to drop substantially to intensify while overcoming the effect of decreasing temperature and salinity. Thus minimum occurs along the Taiwan-Tsushima Current System. Of course, the primary production lower during spring when it is high but the effect is local. Near the Yangtze river mouth and northeastern corner of the Yellow Sea the fresh water input is large enough and dissolved inorganic carbon (DIC) becomes low enough so that becomes lower again.
    Ocean and Polar Research 12/2011; 33(4).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using results from an Earth System model, we investigated change in primary production in the East China Sea, under a global warming scenario. As global warming progresses, the vertical stratification of water becomes stronger, and nutrient supply from the lower part to the upper part is reduced. Consequently, so is the primary production. In addition to the warming trend, there is strong decadal to interdecadal scale variability, and it takes a few decades before the warming trend surpasses natural variability. Thus, it would be very hard to investigate the global warming trend using data of several years' length.
    Ocean and Polar Research 06/2012; 34(2).

Full-text (2 Sources)

Available from
May 27, 2014