Will the Arctic be free of summer ice in 30 years?
|Figure 1. Sea ice minima in September of 1980, 2007 and 2008. Sea ice images from NASA/Goddard Space Flight Center Scientific Visualization StudioThanks to Rob Gerston (GSFC) for providing the data. Composite graphic from NOAA.||Figure 2. Model projections of sea ice thickness when the Arctic is nearly ice free in September, within 30 years. Units for sea ice thickness are meters. Figure from Wang and Overland1|
Arctic sea ice loss is occuring 30 years earlier than was anticipated...
Recent Arctic sea ice coverage is the lowest in the satellite record (since 1979) and is occurring at least 30 years earlier than was anticipated in the recent assessment report issued by the Intergovernmental Panel on Climate Change.
Arctic sea ice extent observed by satellites has been shrinking for the past 30 years. The minimum sea ice extent is seen at the end of summer in 2007, 2008, and 2009 are the three lowest during the satellite era. Although the extent of the 2009 summer sea ice cover was more than that in 2007 and 2008, it is still 25% below the average for 1979-2000.
These sea ice minima open more than 40% of the Arctic Ocean to increased absorption of warmth from the sun near the end of summer. Extensive open water has been observed in the Chukchi Sea, the East Siberian Sea and north of the Barents Sea.
As the summer melt season lengthens and intensifies, there is less sea ice at summer's end. Major delays have occurred in the timing of fall freezeup since 2005.
Over 40% of the thick sea ice that was built up over many winters (nearly 10 feet thick), has melted and is replaced with thinner ice formed in a single year.
Once this process has started, it is difficult to reverse.
What will happen to Arctic sea ice in the next 30 years?
Using the observed 2007/2008 summer sea ice extents as a starting point (Figure 1, above), computer models predict that the Arctic could be nearly sea ice free in summertime within 30 years (Figure 2, above).1
Computer simulations indicate that Arctic sea ice retreat will not continue at a constant rate into the future. Instead they show several abrupt decreases in summer Arctic sea ice cover in the futue. The projections for a likely ice retreat suggests that the Arctic could transition from perennial year-round ice to seasonal winter ice, with numerous implications for the climate system.2
Sea ice thickness, concentration and age is reduced in the warmer Arctic
In Figure 3 (below, left) the blue color indicates areas where the Arctic sea ice concentration3 was reduced by as much as 50% of the amount normally observed in October.
|Figure 3. Anomalies (above) represent October 2010 deviations from normal October sea ice concentration. Figure from National Snow and Ice Data Center.||Figure 4. Sea ice age derived from drift tracking of ice floes for the first week of March in a) 1988, b) 2008, c), 2009, and d) 2010. (Figure courtesy of National Snow and Ice Data Center, J. Maslanik and C. Fowler).|
Figure 4 (above, right) shows how old, thick Arctic sea ice, built up over many years, is being replaced by thinner, younger ice in recent years. The four panels show the age of the sea ice in March for different years. Sea ice age is used as a rough indicator of sea ice thickness.
In 1988, large areas of the Arctic Ocean were covered by multi-year sea ice that is five or more years old (red colors in Figure 4(a)). In 2008, 2009 and 2010, these areas of older sea ice had dwindled to a small strip near the coast from Alaska to Greenland (red colors in Figure 4 (b), (c), and (d)), indicating that in these years, old 5-year sea ice was replaced by younger, thinner and less resilient ice.
The thick component of the perennial ice, called multi-year ice, as detected by satellite data during the winters of 1979–2011 was studied5, and results reveal that the multi-year ice extent and area are declining at a rapid rate of 215.1% per decade and 217.2% per decade, respectively, with a record low value in 2008 followed by higher values in 2009, 2010, and 20115.
The pale areas in Figure 5 (to the right) denote thicker sea ice (3-6 feet or 1-2 meters thick), and dark blue areas denote thinner sea ice (less than 3 feet or 1 meter thick), as computed by models.
The top row of Figure 5 shows conditions for the year when the computer simulated September sea ice extent reachs current values. By the end of winter, much of the central Arctic is covered by sea ice less than 8 feet or 2.5 meters thick (top left). At the end of summer (in September), much of the remaining sea ice in the central Arctic is less than 4 feet or 1.2 meters thick (top right).
The bottom row of Figure 4 shows conditions for the year when the models predict a nearly sea ice-free Arctic, about 30 years later. At the end of winter, much of the modeled sea ice is less than 6.5 feet or 2.0 meters thick (bottom left). At the end of summer, the sea ice that remains is very thin (bottom right).
In the year when the models predict a nearly sea ice-free Arctic, about 30 years from now, only a small area north of the Canadian Archipelago and Greenland (the small white area in the image at the bottom right) retains some sea ice approaching a thickness of 6.6 feet or 2 meters.
See the latest Arctic Report Card update on Sea Ice
Learn more about Computer models and uncertainty in predictions of sea ice loss
References and definitions
1 Wang, M., and J.E. Overland (2009): A sea ice free summer Arctic within 30 years? Geophys. Res. Lett., 36, L07502, doi: 10.1029/2009GL037820.
2 Holland, M.M., C.M. Bitz, and B. Tremblay (2006): Future abrupt reductions in the summer Arctic sea ice. Geophys. Res. Lett., 33, L23503, doi:10.1029/2006GL028024.
3 Sea ice concentration is the amount of sea ice in a given area.
PDF] (accepted 17 May 2011)Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification? Geophys. Res. Lett., doi:10.1029/2011GL047696, in press. [
5 Comiso, Josefino C., 2012: Large Decadal Decline of the Arctic Multiyear Ice Cover. J. Climate, 25, 1176–1193. doi: http://dx.doi.org/10.1175/JCLI-D-11-00113.1 [PDF version]
6 Overland, J.E., and M. Wang (2013): When will the summer Arctic be nearly sea ice free? Geophys. Res. Lett., 40(10), doi: 10.1002/grl.50316, 2097–2101.
7Jeffries, M.O., J.E. Overland, and D.K. Perovich (2013): The Arctic shifts to a new normal. Physics Today, 66(10), 35–40.
8 Overland, J.E., M. Wang, J.E. Walsch, J.C. Stroeve (2013): Future Arctic Climate Changes: Adaptation and Mitigation Timescales. Earth's Future, doi:10.1002/2013EF000162, in press.