Preprints
https://doi.org/10.5194/tc-2020-305
https://doi.org/10.5194/tc-2020-305

  22 Oct 2020

22 Oct 2020

Review status: a revised version of this preprint is currently under review for the journal TC.

Interannual variability in Transpolar Drift ice thickness and potential impact of Atlantification

H. Jakob Belter1, Thomas Krumpen1, Luisa von Albedyll1, Tatiana A. Alekseeva2, Sergei V. Frolov2, Stefan Hendricks1, Andreas Herber1, Igor Polyakov3,4,5, Ian Raphael6, Robert Ricker1, Sergei S. Serovetnikov2, Melinda Webster7, and Christian Haas1 H. Jakob Belter et al.
  • 1Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 2Arctic and Antarctic Research Institute, St. Petersburg, Russian Federation
  • 3International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, USA
  • 4College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, USA
  • 5Finnish Meteorological Institute, Helsinki, Finland
  • 6Thayer School of Engineering at Dartmouth College, Hanover, USA
  • 7Geophysical Institute, University of Alaska Fairbanks, Fairbanks, USA

Abstract. Changes in Arctic sea ice thickness are the result of complex interactions of the dynamic and variable ice cover with atmosphere and ocean. Most of the sea ice exits the Arctic Ocean through Fram Strait, which is why long-term measurements of ice thickness at the end of the Transpolar Drift provide insight into the integrated signals of thermodynamic and dynamic influences along the pathways of Arctic sea ice. We present an updated time series of extensive ice thickness surveys carried out at the end of the Transpolar Drift between 2001 and 2020. Overall, we see a more than 20 % thinning of modal ice thickness since 2001. A comparison with first preliminary results from the international Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) shows that the modal summer thickness of the MOSAiC floe and its wider vicinity are consistent with measurements from previous years. By combining this unique time series with the Lagrangian sea ice tracking tool, ICETrack, and a simple thermodynamic sea ice growth model, we link the observed interannual ice thickness variability north of Fram Strait to increased drift speeds along the Transpolar Drift and the consequential variations in sea ice age and number of freezing degree days. We also show that the increased influence of upward-directed ocean heat flux in the eastern marginal ice zones, termed Atlantification, is not only responsible for sea ice thinning in and around the Laptev Sea, but also that the induced thickness anomalies persist beyond the Russian shelves and are potentially still measurable at the end of the Transpolar Drift after more than a year. With a tendency towards an even faster Transpolar Drift, winter sea ice growth will have less time to compensate the impact of Atlantification on sea ice growth in the eastern marginal ice zone, which will increasingly be felt in other parts of the sea ice covered Arctic.

H. Jakob Belter et al.

 
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H. Jakob Belter et al.

H. Jakob Belter et al.

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Short summary
Summer sea ice thickness observations based on electromagnetic induction measurements north of Fram Strait show a 20 % reduction in mean and modal ice thickness between 2001–2020. The observed variability is caused by changes in drift speeds and consequential variations in sea ice age and number of freezing degree days. Increased ocean heat fluxes measured upstream in the source regions of Arctic ice seem to precondition ice thickness, which is potentially still measurable more than a year later.