Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene

Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel, M.; Jaccard, Samuel; Tiedemann, Ralf; Haug, Gerald, H. (2017). Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene. Science Advances, 3(9), e1700156. American Association for the Advancement of Science 10.1126/sciadv.1700156

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An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, the world’s largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox- sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implica- tions for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.

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:

2375-2548

Publisher:

American Association for the Advancement of Science

Funders:

[4] Swiss National Science Foundation

Projects:

Projects 4 not found.

Language:

English

Submitter:

Samuel Jaccard

Date Deposited:

10 Nov 2017 10:44

Last Modified:

14 Mar 2018 15:00

Publisher DOI:

10.1126/sciadv.1700156

PubMed ID:

28924606

BORIS DOI:

10.7892/boris.105414

URI:

https://boris.unibe.ch/id/eprint/105414

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