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

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doi: 10.1073/pnas.1600616113
Author(s): Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel L.; Marcantonio, Franco
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Other:
University of Bern, Switzerland
Volume Title: Proceedings of the National Academy of Sciences of the United States of America
Source: Proceedings of the National Academy of Sciences of the United States of America, 113(22), p.6119-6124. Publisher: National Academy of Sciences, Washington, DC, United States. ISSN: 0027-8424 CODEN: PNASA6
Note: In English. LDEO Contrib. 7999. 65 refs.; illus., incl. sketch map
Summary: 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.
Year of Publication: 2016
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Actinides; Alkaline earth metals; Barium; Carbon; Cenozoic; Clastic sediments; Cores; Dust; East Pacific; Equatorial Pacific; Fertilization; Framework silicates; Glacial environment; Holocene; Iron; Isotope ratios; Isotopes; Leg 138; Metals; Middle Pleistocene; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 849; Ocean Drilling Program; Opal; Organic compounds; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Pleistocene; Quaternary; Radioactive isotopes; Residence time; Sediments; Silica minerals; Silicates; Stable isotopes; Th-230; Th-232; Thorium; Transport; U-234; Upper Pleistocene; Upwelling; Uranium; West Pacific; Wind transport
Coordinates: N001800 N001800 E1592400 E1592400
N000600 N000600 W1392400 W1392400
N001058 N001100 W1103110 W1103111
Record ID: 2019003219
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.