Determining the natural length of the current interglacial

Journal name:
Nature Geoscience
Volume:
5,
Pages:
138–141
Year published:
DOI:
doi:10.1038/ngeo1358
Received
Accepted
Published online
Corrected online

No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv (ref. 1). Indeed, model experiments suggest that in the current orbital configuration—which is characterized by a weak minimum in summer insolation—glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv (refs 2, 3, 4). However, the precise CO2 threshold4, 5, 6 as well as the timing of the hypothetical next glaciation7 remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice-rafted debris. The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing7. Assuming that ice growth mainly responds to insolation and CO2 forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5ppmv.

At a glance

Figures

  1. Astronomical parameters 100[thinsp]kyr after present[mdash]800[thinsp]kyr BP and palaeoclimatic records 0-800[thinsp]kyr BP.
    Figure 1: Astronomical parameters 100kyr after present—800kyr BP and palaeoclimatic records 0–800kyr BP.

    a, Eccentricity29; b, precession index, plotted on an inverse vertical axis29; c, obliquity29; d, 21 June insolation 65°N (ref.  29); e, δ18Obenthic record from the LR04 stack28; f, atmospheric CO2 concentration in Antarctic ice cores12; g, atmospheric CH4 concentration in the Antarctic EDC ice core13; h, δD composition of ice in the EDC ice core18. Marine Isotopic Stages and sub-Stages corresponding to interglacials are indicated. Ages in parentheses denote years after present. The dashed line indicates the current 21 June insolation level at 65°N.

  2. Two types of interglacial according to structure: MIS9 and MIS11.
    Figure 2: Two types of interglacial according to structure: MIS9 and MIS11.

    a, Precession index, plotted on an inverse vertical axis29; b, obliquity29; c, δ18Obenthic record from the LR04 stack28; d, atmospheric CO2 concentration in Antarctic ice cores12; e, atmospheric CH4 concentration in the EDC ice core13; f, δD composition of ice in the EDC ice core18.

  3. Alignment of the past and future 30[thinsp]kyr (grey line) and a 60-kyr interval encompassing MIS19 (dotted line).
    Figure 3: Alignment of the past and future 30kyr (grey line) and a 60-kyr interval encompassing MIS19 (dotted line).

    a, Precession index, plotted on an inverse vertical axis29; b, 21 June insolation at 65°N (ref. 29); c, obliquity29; d, summer energy at 65°N, defined as the sum of the diurnal average insolation on days exceeding 300Wm−2 (ref. 30); e, δ18Obenthic record from the LR04 stack28; f, δD composition of ice in the EDC ice core18; g, atmospheric CO2 concentration in Antarctic ice cores12; h, atmospheric CH4 concentration in the EDC ice core13. Ages in parentheses denote years after present.

  4. MIS19 palaeoclimatic records.
    Figure 4: MIS19 palaeoclimatic records.

    a, 21 June insolation at 65°N (ref. 29); b obliquity29; c, δ18Obenthic record from ODP 983 (ref. 25); d, ODP 983 ice-rafted detritus (IRD) content (numbers per gram)26; e, δ18Oplanktonic record from ODP 983 (ref. 25); f, atmospheric CH4 concentration in the EDC ice core13; g, atmospheric CO2 concentration in the EDC ice core12; h, δD composition of ice in the EDC ice core18. Marine and ice-core records plotted on their own timescales. Marine Isotope Stages and sub-Stages and Antarctic Isotope Maxima (AIMs) are indicated. Dashed lines denote ODP 983–EDC correlation of events. Horizontal bars indicate estimates of interglacial duration (see main text).

Change history

Corrected online 10 January 2012
The PDF of this Letter originally appeared with the incorrect 'published online' date of 8 January 2012; the actual date it went live was 9 January 2012. The date is now correct on all versions of the Letter.

References

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Affiliations

  1. Environmental Change Research Centre, Department of Geography, University College London, London WC1E 6BT, UK

    • P. C. Tzedakis
  2. Department of Geological Sciences, University of Florida, Gainesville, Florida 36211, USA

    • J. E. T. Channell
  3. Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK

    • D. A. Hodell &
    • L. C. Skinner
  4. Department of Earth Science and the Bjerknes Centre for Climate Research, University of Bergen, N-5007 Bergen, Norway

    • H. F. Kleiven
  5. UNI Research AS, N-5007 Bergen, Norway

    • H. F. Kleiven

Contributions

All authors contributed to the ideas developed in the paper. P.C.T. wrote the paper, with contributions from the other authors.

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The authors declare no competing financial interests.

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