Scientific American and others cover the study you find below.
First the Scientific American article:
http://www.scientificamerican.com/article/geoengineering-would-not-work-in-all-oceans/?wt.mc=SA_Twitter-Share
http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html
No iron fertilization in the equatorial Pacific Ocean during the last
ice age
* K. M. Costa
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-1>,
* J. F. McManus
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-2>,
* R. F. Anderson
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-3>,
* H. Ren
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-4>,
* D. M. Sigman
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-5>,
* G. Winckler
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-6>,
* M. Q. Fleisher
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-7>,
* F. Marcantonio
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-8>
* & A. C. Ravelo
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#auth-9>
* Affiliations
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#affil-auth>
* Contributions
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#contrib-auth>
* Corresponding author
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#corres-auth>
Nature
529,
519–522
(28 January 2016)
doi:10.1038/nature16453
The equatorial Pacific Ocean is one of the major high-nutrient,
low-chlorophyll regions in the global ocean. In such regions, the
consumption of the available macro-nutrients such as nitrate and
phosphate is thought to be limited in part by the low abundance of the
critical micro-nutrient iron^1
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref1>
. Greater atmospheric dust deposition^2
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref2>
could have fertilized the equatorial Pacific with iron during the last
ice age—the Last Glacial Period (LGP)—but the effect of increased
ice-age dust fluxes on primary productivity in the equatorial Pacific
remains uncertain^3
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref3>,
4
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref4>,
5
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref5>,
6
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref6>
. Here we present meridional transects of dust (derived from the ^232 Th
proxy), phytoplankton productivity (using opal, ^231 Pa/^230 Th and
excess Ba), and the degree of nitrate consumption (using
foraminifera-bound δ^15 N) from six cores in the central equatorial
Pacific for the Holocene (0–10,000 years ago) and the LGP (17,000–27,000
years ago). We find that, although dust deposition in the central
equatorial Pacific was two to three times greater in the LGP than in the
Holocene, productivity was the same or lower, and the degree of nitrate
consumption was the same. These biogeochemical findings suggest that the
relatively greater ice-age dust fluxes were not large enough to provide
substantial iron fertilization to the central equatorial Pacific. This
may have been because the absolute rate of dust deposition in the LGP
(although greater than the Holocene rate) was very low. The lower
productivity coupled with unchanged nitrate consumption suggests that
the subsurface major nutrient concentrations were lower in the central
equatorial Pacific during the LGP. As these nutrients are today
dominantly sourced from the Subantarctic Zone of the Southern Ocean, we
propose that the central equatorial Pacific data are consistent with
more nutrient consumption in the Subantarctic Zone, possibly owing to
iron fertilization as a result of higher absolute dust fluxes in this
region^7
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref7>,
8
<http://www.nature.com/nature/journal/v529/n7587/full/nature16453.html#ref8>
. Thus, ice-age iron fertilization in the Subantarctic Zone would have
ultimately worked to lower, not raise, equatorial Pacific productivity.
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