Article

Climate Dynamics

, Volume 34, Issue 6, pp 781-795

Unprecedented low twentieth century winter sea ice extent in the Western Nordic Seas since A.D. 1200

  • M. Macias FauriaAffiliated withBiogeoscience Institute, University of CalgaryDepartment of Geology, University of HelsinkiRovaniemi Research Station, Finnish Forest InstituteDepartment of Ecology, Faculty of Biology, University of Barcelona Email author 
  • , A. GrinstedAffiliated withArctic Centre, University of LaplandCentre for Ice and Climate, Niels Bohr Institute, University of Copenhagen
  • , S. HelamaAffiliated withDepartment of Geology, University of Helsinki
  • , J. MooreAffiliated withArctic Centre, University of LaplandThule Institute, University of OuluCollege of Global Change and Earth System Science, Beijing Normal University
  • , M. TimonenAffiliated withRovaniemi Research Station, Finnish Forest Institute
  • , T. MartmaAffiliated withInstitute of Geology, Tallinn University of Technology
  • , E. IsakssonAffiliated withPolar Environmental Centre, Norwegian Polar Institute
  • , M. EronenAffiliated withDepartment of Geology, University of Helsinki

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Abstract

We reconstructed decadal to centennial variability of maximum sea ice extent in the Western Nordic Seas for A.D. 1200–1997 using a combination of a regional tree-ring chronology from the timberline area in Fennoscandia and δ18O from the Lomonosovfonna ice core in Svalbard. The reconstruction successfully explained 59% of the variance in sea ice extent based on the calibration period 1864–1997. The significance of the reconstruction statistics (reduction of error, coefficient of efficiency) is computed for the first time against a realistic noise background. The twentieth century sustained the lowest sea ice extent values since A.D. 1200: low sea ice extent also occurred before (mid-seventeenth and mid-eighteenth centuries, early fifteenth and late thirteenth centuries), but these periods were in no case as persistent as in the twentieth century. Largest sea ice extent values occurred from the seventeenth to the nineteenth centuries, during the Little Ice Age (LIA), with relatively smaller sea ice-covered area during the sixteenth century. Moderate sea ice extent occurred during thirteenth–fifteenth centuries. Reconstructed sea ice extent variability is dominated by decadal oscillations, frequently associated with decadal components of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO), and multi-decadal lower frequency oscillations operating at ~50–120 year. Sea ice extent and NAO showed a non-stationary relationship during the observational period. The present low sea ice extent is unique over the last 800 years, and results from a decline started in late-nineteenth century after the LIA.

Keywords

Sea ice Paleoclimatology Nordic seas Global warming Ice core Dendroclimatology Svalbard Fennoscandia NAO AO Little Ice Age