Mid Holocene origin of the sea-surface salinity low in the subarctic North Pacific |
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| Institution: | 1. Institut für Geowissenschaften, University of Kiel, Olshausenstr. 40, D-24098 Kiel, Germany;2. Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK;3. Department of Geology, Royal Holloway University of London, Egham, TW20 OEX, UK;4. Leibniz Laboratory, University of Kiel, D-24098 Kiel, Germany;1. Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, CB2 3EQ, UK;2. Uni Research, Uni Climate and Bjerknes Centre for Climate Research, Bergen, Norway;3. International Pacific Research Centre and Department of Oceanography, University of Hawai''i, Honolulu, USA;4. Climate Change Research Centre, University of New South Wales, Sydney, Australia;5. ARC Centre of Excellence for Climate System Science, Australia;1. Geosciences Department, Williams College, 947 Main Street, Williamstown, MA 01267, USA;2. Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, CA 95064, USA;3. College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA;4. e4 Sciences, 27 Glen Road, Sandy Hook, CT 06482, USA;5. School for Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA;1. Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK;2. LSCE/IPSL Laboratoire, CNRS–CEA–UVSQ, 91198 Gif-sur-Yvette, France;1. Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, United States;2. Marine Science Institute, University of California, Santa Barbara, CA 93106, United States;1. Institute of Geosciences, Christian-Albrechts-University, Ludewig-Meyn-Str. 10, D-24118 Kiel, Germany;2. Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, D-27568 Bremerhaven, Germany;1. Department of Marine and Coastal Sciences, and Department of Earth and Planetary Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901, USA;2. Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA;3. Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA;4. School for Marine Science and Technology, University of Massachusetts Dartmouth, New Bedford, MA 02747, USA |
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| Abstract: | IMAGES core MD01-2416 (51°N, 168°E) provides the first centennial-scale multiproxy record of Holocene variation in North Pacific sea-surface temperature (SST), salinity, and biogenic productivity. Our results reveal a gradual decrease in subarctic SST by 3–5 °C from 11.1 to 4.2 ka and a stepwise long-term decrease in sea surface salinity (SSS) by 2–3 p.s.u. Early Holocene SSS were as high as in the modern subtropical Pacific. The steep halocline and stratification that is characteristic of the present-day subarctic North Pacific surface ocean is a fairly recent feature, developed as a product of mid-Holocene environmental change. High SSS matched a salient productivity maximum of biogenic opal during Bølling-to-Early Holocene times, reaching levels similar to those observed during preglacial times in the warm mid-Pliocene prior to 2.73 Ma. Similar productivity spikes marked every preceding glacial termination of the last 800 ka, indicating recurrent short-term events of mid-Pliocene-style intense upwelling of nutrient-rich Pacific Deepwater in the Pleistocene. Such events led to a repeated exposure of CO2-rich deepwater at the ocean surface facilitating a transient CO2 release to the atmosphere, but the timing and duration of these events repudiate a long-term influence of the subarctic North Pacific on global atmospheric CO2 concentration. |
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