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

Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel; Marcantonio, Franco (2016). Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years. Proceedings of the National Academy of Sciences of the United States of America - PNAS, 113(22), pp. 6119-6124. National Academy of Sciences NAS 10.1073/pnas.1600616113

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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.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Jaccard, Samuel

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0027-8424

Publisher:

National Academy of Sciences NAS

Language:

English

Submitter:

Samuel Jaccard

Date Deposited:

20 Jun 2016 13:14

Last Modified:

11 Jul 2016 11:14

Publisher DOI:

10.1073/pnas.1600616113

PubMed ID:

27185933

BORIS DOI:

10.7892/boris.83461

URI:

https://boris.unibe.ch/id/eprint/83461

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