Letter

Reconstructed changes in Arctic sea ice over the past 1,450 years

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Published online:

Abstract

Arctic sea ice extent is now more than two million square kilometres less than it was in the late twentieth century, with important consequences for the climate, the ocean and traditional lifestyles in the Arctic1,2. Although observations show a more or less continuous decline for the past four or five decades3,4, there are few long-term records with which to assess natural sea ice variability. Until now, the question of whether or not current trends are potentially anomalous5 has therefore remained unanswerable. Here we use a network of high-resolution terrestrial proxies from the circum-Arctic region to reconstruct past extents of summer sea ice, and show that—although extensive uncertainties remain, especially before the sixteenth century—both the duration and magnitude of the current decline in sea ice seem to be unprecedented for the past 1,450 years. Enhanced advection of warm Atlantic water to the Arctic6 seems to be the main factor driving the decline of sea ice extent on multidecadal timescales, and may result from nonlinear feedbacks between sea ice and the Atlantic meridional overturning circulation. These results reinforce the assertion that sea ice is an active component of Arctic climate variability and that the recent decrease in summer Arctic sea ice is consistent with anthropogenically forced warming.

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Acknowledgements

This work was supported jointly by the Canadian Foundation for Climate and Atmospheric Sciences (Polar Climate Stability Network) and the Natural Sciences and Engineering Research Council of Canada.

Author information

Affiliations

  1. Centro de Estudios Avanzados en Zonas Áridas, Benavente 980, Casilla 554, La Serena, 1720170, Chile

    • Christophe Kinnard
  2. Geological Survey of Canada, NRCAN, Ottawa, Ontario, K1A 0E8, Canada

    • Christian M. Zdanowicz
    •  & David A. Fisher
  3. Norwegian Polar Institute, FRAM – High North Research Centre on Climate and the Environment, NO-9296 Tromsø, Norway

    • Elisabeth Isaksson
  4. GEOTOP, Université du Québec à Montréal, PO Box 8888, Montréal, Québec, H3C 3P8, Canada

    • Anne de Vernal
  5. Byrd Polar Research Center, Ohio 43210, Columbus, USA

    • Lonnie G. Thompson

Authors

  1. Search for Christophe Kinnard in:

  2. Search for Christian M. Zdanowicz in:

  3. Search for David A. Fisher in:

  4. Search for Elisabeth Isaksson in:

  5. Search for Anne de Vernal in:

  6. Search for Lonnie G. Thompson in:

Contributions

C.K. conducted all data preparation and analyses. C.M.Z. and D.A.F. instigated and directed the research and contributed to the interpretation. E.I., A.deV. and L.G.T. contributed data and participated in the interpretation of results. All authors contributed to manuscript preparation.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Christophe Kinnard.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    The file contains Supplementary Figures 1-11 with legends, Supplementary Methods, Supplementary Table 1, a Supplementary Discussion and additional references.

Excel files

  1. 1.

    Supplementary Data 1

    This file contains the original proxy data used in the study.

  2. 2.

    Supplementary Data 2

    This file contains smoothed (5-year lowpass) and infilled proxy records used for calibration against historical sea-ice data.

  3. 3.

    Supplementary Data 3

    This file contains 1-year and 5-year smoothed historical August sea-ice extent used in this study.

  4. 4.

    Supplementary Data 4

    This file contains all data plotted in Figure 3 of the article.

Zip files

  1. 1.

    Supplementary Data 5

    This file contains Matlab codes/ calibaration comprising: calibrateproxies.m - steps for PLS calibration of historical sea ice extent with the proxy network; call_calibrateproxies.m - script to load matlab data and call calibrateproxies.m / associated codes; Various Matlab functions called by calibrateproxies.m

  2. 2.

    Supplementary Data 6

    This file contains Matlab data comprising: AugustIceExtentWCPOL_infilled.mat: August historical sea ice extent (SeaIceExtent.xls) in Matlab format; PROXIESpre1995_infilled_withnoise.mat: smoothed (5-year lowpass) and infilled proxy records (ProxyData_5YR_infilled.xls); PROXYMETADATA1.mat: Matlab structure containing information on proxy records, called by calibrateproxies.m.

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