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Proc Natl Acad Sci U S A. 2016 May 31;113(22):6119-24. doi: 10.1073/pnas.1600616113. Epub 2016 May 16.

Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years.

Author information

1
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964; Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027; winckler@ldeo.columbia.edu.
2
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964; Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027;
3
Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland; Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland;
4
Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843.

Abstract

Biological productivity in the equatorial Pacific is relatively high compared with other low-latitude regimes, especially east of the dateline, where divergence driven by the trade winds brings nutrient-rich waters of the Equatorial Undercurrent to the surface. The equatorial Pacific is one of the three principal high-nutrient low-chlorophyll ocean regimes where biological utilization of nitrate and phosphate is limited, in part, by the availability of iron. Throughout most of the equatorial Pacific, upwelling of water from the Equatorial Undercurrent supplies far more dissolved iron than is delivered by dust, by as much as two orders of magnitude. Nevertheless, recent studies have inferred that the greater supply of dust during ice ages stimulated greater utilization of nutrients within the region of upwelling on the equator, thereby contributing to the sequestration of carbon in the ocean interior. Here we present proxy records for dust and for biological productivity over the past 500 ky at three sites spanning the breadth of the equatorial Pacific Ocean to test the dust fertilization hypothesis. Dust supply peaked under glacial conditions, consistent with previous studies, whereas proxies of export production exhibit maxima during ice age terminations. Temporal decoupling between dust supply and biological productivity indicates that other factors, likely involving ocean dynamics, played a greater role than dust in regulating equatorial Pacific productivity.

KEYWORDS:

carbon; climate change; eolian dust; export production; iron fertilization

PMID:
27185933
PMCID:
PMC4896667
DOI:
10.1073/pnas.1600616113
[Indexed for MEDLINE]
Free PMC Article

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