Abstract 1 of 2 from Science
Super ENSO and Global Climate Oscillations at Millennial Time Scales
Lowell Stott,1* Christopher Poulsen,1 Steve Lund,1 Robert Thunell2
The late Pleistocene history of seawater temperature and salinity variability in the western tropical
Pacific warm pool is reconstructed from oxygen isotope (18O) and magnesium/calcium composition of
planktonic foraminifera. Differentiating the calcite 18O record into components of temperature and local
water 18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over
Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials.
The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere
system analogous to modern El Niño-Southern Oscillation (ENSO). El Niño conditions correlate with
stadials at high latitudes, whereas La Niña conditions correlate with interstadials. Millennial-scale shifts
in atmospheric convection away from the western tropical Pacific may explain many paleo-observations,
including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean
variability that have tropical source functions that are negatively correlated with El Niño.
1 Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los
Angeles, CA 90089, USA.
2 Department of Geological Science, University of South Carolina, 700 Sumter Street, Columbia, SC
29208, USA.
* To whom correspondence should be addressed. E-mail: stott@usc.edu
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Abstract 2 of 2
Southern Hemisphere and Deep-Sea Warming Led Deglacial Atmospheric CO2 Rise and Tropical
Warming
Lowell Stott,1* Axel Timmermann,2 Robert Thunell3
Establishing what caused Earth's largest climatic changes in the past requires a precise knowledge of
both the forcing and the regional responses. We determined the chronology of high- and low-latitude
climate change at the last glacial termination by radiocarbon dating benthic and planktonic foraminiferal
stable isotope and magnesium/calcium records from a marine core collected in the western tropical
Pacific. Deep-sea temperatures warmed by 2°C between 19 and 17 thousand years before the present
(ky B.P.), leading the rise in atmospheric CO2 and tropical–surface-ocean warming by 1000 years. The
cause of this deglacial deep-water warming does not lie within the tropics, nor can its early onset
between 19 and 17 ky B.P. be attributed to CO2 forcing. Increasing austral-spring insolation combined
with sea-ice albedo feedbacks appear to be the key factors responsible for this warming.
1 Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.
2 International Pacific Research Center (IPRC), School of Ocean and Earth Science and Technology,
University of Hawaii, Honolulu, HI 96822, USA.
3 Department of Geological Sciences, University of South Carolina, Columbia, SC 29208, USA.
* To whom correspondence should be addressed. E-mail: stott@usc.edu
Full Text » | PDF » |
Super ENSO and Global Climate Oscillations at Millennial Time Scales
Lowell Stott,1* Christopher Poulsen,1 Steve Lund,1 Robert Thunell2
The late Pleistocene history of seawater temperature and salinity variability in the western tropical
Pacific warm pool is reconstructed from oxygen isotope (18O) and magnesium/calcium composition of
planktonic foraminifera. Differentiating the calcite 18O record into components of temperature and local
water 18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over
Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials.
The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere
system analogous to modern El Niño-Southern Oscillation (ENSO). El Niño conditions correlate with
stadials at high latitudes, whereas La Niña conditions correlate with interstadials. Millennial-scale shifts
in atmospheric convection away from the western tropical Pacific may explain many paleo-observations,
including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean
variability that have tropical source functions that are negatively correlated with El Niño.
1 Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los
Angeles, CA 90089, USA.
2 Department of Geological Science, University of South Carolina, 700 Sumter Street, Columbia, SC
29208, USA.
* To whom correspondence should be addressed. E-mail: stott@usc.edu
--------------------------------------------------------------------------------
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Back to Top
Abstract 2 of 2
Southern Hemisphere and Deep-Sea Warming Led Deglacial Atmospheric CO2 Rise and Tropical
Warming
Lowell Stott,1* Axel Timmermann,2 Robert Thunell3
Establishing what caused Earth's largest climatic changes in the past requires a precise knowledge of
both the forcing and the regional responses. We determined the chronology of high- and low-latitude
climate change at the last glacial termination by radiocarbon dating benthic and planktonic foraminiferal
stable isotope and magnesium/calcium records from a marine core collected in the western tropical
Pacific. Deep-sea temperatures warmed by 2°C between 19 and 17 thousand years before the present
(ky B.P.), leading the rise in atmospheric CO2 and tropical–surface-ocean warming by 1000 years. The
cause of this deglacial deep-water warming does not lie within the tropics, nor can its early onset
between 19 and 17 ky B.P. be attributed to CO2 forcing. Increasing austral-spring insolation combined
with sea-ice albedo feedbacks appear to be the key factors responsible for this warming.
1 Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.
2 International Pacific Research Center (IPRC), School of Ocean and Earth Science and Technology,
University of Hawaii, Honolulu, HI 96822, USA.
3 Department of Geological Sciences, University of South Carolina, Columbia, SC 29208, USA.
* To whom correspondence should be addressed. E-mail: stott@usc.edu
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