We summarize the latest results on the rapid changes that are occurring to Arctic sea ice thickness and extent, the reasons for them, and the methods being used to monitor the changing ice thickness. Arctic sea ice extent had been shrinking at a relatively modest rate of 3–4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer 2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million km2. Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of mass from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques that show the greatest promise on different spatial and temporal scales, and for different purposes. We show results from some recent work from submarines, and speculate that the trends towards retreat and thinning will inevitably lead to an eventual loss of all ice in summer, which can be described as a ‘tipping point’ in that the former situation, of an Arctic covered with mainly multi-year ice, cannot be retrieved.
KeywordsIce cover Ice thickness Multi-year ice Ice loss
This is a contribution to the Arctic Tipping Points project (www.eu-atp.org) funded by FP7 of the European Union (contract #226248). The manuscript was improved by three anonymous reviewers.
- ACIA. 2005. Arctic climate impact assessment. Impacts of a warming Arctic. Cambridge: Cambridge University Press.Google Scholar
- Amundrud, T.L., H., Melling, R.G. Ingram, and S.E. Allen. 2006. The effect of structural porosity on the ablation of sea ice ridges. Journal of Geophysical Research 111: C06004. doi: 10.1029/2005JC002895.
- Atkinson, C.P., A.T. Wells, B. Shina, and V.O. Ivchenko. 2009. Rapid ocean wave teleconnections linking Antarctic salinity anomalies to the equatorial ocean-atmosphere system. Geophysical Research Letters 36: L08603. doi: 10.1029/2008GL036976.
- Francois, R.E., and W.K. Nodland 1972. Unmanned Arctic Research Submersible (UARS) system development and test report. Univ. Washington, Applied Physics Lab., Tech. Rept. APL-UW 7219.Google Scholar
- Hautaniemi, H., M. Oksama, J. Multala, M. Leppäranta, K. Riska, and O. Salmela. 1994. Airborne electromagnetic mapping of ice thickness in the Baltic Sea. Proceedings IAHR Symposium, Trondheim, Norway. Google Scholar
- NSIDC. 2007. from http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html.
- Parkinson, C.L., D.J. Cavalieri, P. Gloersen, H.J. Zwally, and J.C. Comiso. 1999. Arctic sea ice extents, areas, and trends, 1978–1996. Journal of Geophysical Research 104: 20837–20856.Google Scholar
- Rossiter, J.R., and J.S. Holladay. 1994. Ice-thickness measurement. In Remote sensing of sea ice and icebergs, ed. S. Haykin, E.O. Lewis, R.K. Raney, and J.R. Rossiter, 141–176. New York: Wiley.Google Scholar
- Tonge, E.M. 1992. An incremental approach to AUVs. Proceedings Oceanology International’92, Brighton, 10–13 March 1992. Spearhead Exhibitions 1.Google Scholar
- Wadhams, P., and J.C. Comiso. 1992. The ice thickness distribution inferred using remote sensing techniques. In Microwave remote sensing of sea ice. ed. F. Carsey, Geophysical Monograph 68, American Geophysical Union, Washington, 375–383.Google Scholar
- Wadhams, P. 1997b. Variability of Arctic sea ice thickness—statistical significance and its relationship to heat flux. In Operational oceanography, The challenge for European co-operation, 368–384. Elsevier.Google Scholar
- Wadhams, P. 2008. Arctic sea ice changes under global warming. Proceedings ICETECH 2008, International Conference on Performance of Ships and Structures in Ice, Banff, July 20–23 2008. Society of Naval Architects and Marine Engineers, ISBN 978-0-9780896-1.Google Scholar
- Wadhams, P., N. Hughes, and J. Rodrigues. 2011. Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects. Journal of Geophysical Research 116: C00E02. doi: 10.1029/2011JC006982.