Sea Ice and Freshwater Ice Assessments

2013 Arctic Sea Ice


Jeff Key (NOAA)
25 July 2014

The average Arctic sea ice extent in September 2012 was 3.63 million square kilometers; in September 2013 it was 5.35 million square kilometers (National Snow and Ice Data Center, NSIDC), or a 48% increase in the ice extent (Figures 1, 2, and 3). Despite this significant rebound, the extent of sea ice in September 2013 was the sixth lowest in the satellite record (NSIDC) and the largest September minimum ice extent since 2006. However, the 2013 summer minimum extent was still 1.12 million km2 below the 1981-2010 average minimum ice extent. Therefore, this was more a return from a prior extreme, and a return to a slower long-term decline, than a recovery to a normal state. Most of this rebound occurred from the East Siberian and Chukchi Seas, where decreases in ice concentration were greatest over the last three decades.

Figure 1
Figure 1: Top: Image of Arctic sea ice on September 16, 2012, the day that the National Snow and Ice Data Center identified to be the minimum reached in 2012. The sea ice is shown with a blue tint. Data are from the U.S. Defense Meteorological Satellite Program's Special Sensor Microwave/Imager. Bottom: Arctic sea ice on August 15, 2013. Data are from the Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument aboard the Global Change Observation Mission 1st-Water "SHIZUKU" (GCOM-W1) satellite. AMSR2 data are courtesy of the Japan Aerospace Exploration Agency (JAXA). Credit: NASA Goddard Space Flight Center Scientific Visualization Studio
Figure 2
Figure 2: Sea ice concentration anomaly for September 2013 from SSMIS observations relative to the 2002-2012 mean.
Figure 3
Figure 3: Time series of ice extent anomalies in March and September. Anomalies are relative to the mean values for the period 1981-2010. Black and red lines are least squares linear regression lines. The slopes of these lines indicate ice losses of -2.6% and -13.7% per decade in March and September, respectively. From the Arctic Report Card 2013.

While the minimum sea ice extent returned from the 2012 minimum, the distribution of ice age continued to favor first-year ice. In March 2013 first-year ice comprised 78% of the ice pack, compared to 75% in 2012. For comparison, the March 1988 ice pack was composed of 58% first-year ice.

Ice thickness observations March 2012 and March 2013 are available from the NASA IceBridge aircraft campaign. The same flight paths over the Beaufort Sea in 2012 and 2013 show that the mean sea ice thicknesses in 2012 (1.84 m) and in 2013 (1.81 m) are similar. However, the distributions show a lower frequency of ice with thicknesses less than 1 m in 2013 than in 2012, a greater frequency of ice with thicknesses between 1 m and 2.5 m in 2013, and a marginally lower frequency of ice thicker than 2.5 m in 2013. Overall, there is 6% more sea ice thicker than 1.5 m in 2013 than in 2012. On a broader spatial scale, the March 2012 and 2013 ice thickness differences from IceBridge data have been confirmed with ice thickness estimates from the European Space Agency’s CryoSat-2 satellite. CryoSat-2 is a radar altimeter that measures sea ice freeboard. Preliminary sea ice thickness estimates from the Alfred Wegener Institute show positive ice thickness differences (March 2013 minus March 2012) over most of the Beaufort, and Chukchi Seas. The CryoSat-2 ice thicknesses also indicate that the ice grew more from January to March in the East Siberian and Beaufort Seas in 2013 than in 2012 (not shown).

Figure 4
Figure 4: (a) Ice thickness probability distribution function in 2012 (thin line) and in 2013 (thick line) based on data from IceBridge flights north of Alaska. (b) Difference in ice thickness in March 2013 and March 2012 based on CryoSat-2 satellite altimeter data.

What caused this short-term variability? A variety of factors, including ice dynamics, oceanic and atmospheric heat transport, wind, and solar insolation anomalies, may have contributed to the rebound. See the 2013 atmosphere assessment for a discussion of the role of wintertime clouds on the summer 2013 sea ice.


Sources and References


  • Perovich, D., S. Gerland, S. Hendricks, W. Meier, M. Nicolaus, J. Richter-Menge, M. Tschudi, 2014, Sea Ice, in the Arctic Report Card: Update for 2013. http://www.arctic.noaa.gov/reportcard/sea_ice.html.
  • The German CryoSat Office of the Alfred Wegener Institute provides their preliminary ice thickness estimates to the scientific community for evaluation.
  • Laxon, S. W., and 14 others, 2013: CryoSat-2 estimates of Arctic sea ice thickness and volume, Geophys. Res. Lett., 40, doi: 10.1002/grl50193.
  • Maslanik J. A., C. Fowler, J. Stroeve, S. Drobot, J. Zwally, D. Yi, and W. Emery, 2007: A younger, thinner Arctic ice cover: Increased potential for rapid, extensive sea ice loss, Geophys. Res. Lett., 34, doi:10.1029/2007GL032043.
  • Maslanik, J., J. Stroeve, C. Fowler, and W. Emery, 2011: Distribution and trends in Arctic sea ice age through spring 2011. Geophys. Res. Lett., 38, doi:10.1029/2011GL047735.
  • Tschudi, M. A., C. Fowler, J. A. Maslanik, and J. A. Stroeve, 2010: Tracking the movement and changing surface characteristics of Arctic sea ice. IEEE J. Selected Topics in Earth Obs. and Rem. Sens., 3, doi: 10.1109/JSTARS.2010.2048305.

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