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

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, theworld’s largest ocean,where relatively fresh surface waters inhibitNorth Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO 2 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. Redoxsensitive 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 tomore » deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.« less
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [5] ;  [6]
  1. George Mason Univ., Fairfax, VA (United States). Center for Ocean-Land-Atmosphere Studies, Department of Atmospheric, Oceanic, and Earth Sciences; Yale Univ., New Haven, CT (United States). Department of Geology and Geophysics
  2. Yale Univ., New Haven, CT (United States). Department of Geology and Geophysics
  3. Princeton Univ., NJ (United States). Department of Geosciences
  4. University of Bern (Switzerland). Institute of Geological Sciences and Oeschger Center for Climate Change Research
  5. Alfred Wegener Institute, Bremerhaven (Germany)
  6. Max-Planck Institute for Chemistry, Mainz (Germany); ETH Zurich (Switzerland). Geological Institute, Department of Earth Science
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 3; Journal Issue: 9; Journal ID: ISSN 2375-2548
Research Org:
George Mason Univ., Fairfax, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
OSTI Identifier: