by Malte Humpert The Arctic Institute presents the first interactive graphs for Arctic sea ice extent and volume. The graphs can be found permanently at Arctic Sea Ice Extent and Volume above. The two charts depict monthly Arctic sea ice extent for the years 2007-2011 and Arctic sea ice volume for the year 2005-2011. Both graphs also show the monthly average for the years 1979-1990 and 1979-2000 as a reference point. A mouseover effect allows the user to retrieve data points directly by pointing the mouse at coordinates in the chart. The graphs are based on the Sea Ice Index published by the National Snow and Ice Data Center and PIOMAS Daily Ice Volume Data published by the Polar Science Center.
Arctic Sea Ice Extent (current as of 12/20/2011)
The graph depicts monthly Arctic sea ice extent for 2007-2011 and the monthly averages for 1979-1990 and 1979-2000. The decline of sea ice over the past decade has been most prominent during the months of July-October. The annual minimum extent usually occurs during the month of September and the lowest monthly average was measured in September 2007. The monthly figure was 40.8 percent below the average for the period 1979-1990. Ice extent recovered during 2008 and 2009 to yet again decline in 2010 and 2011. The 2011 September minimum ice extent came close to the record low of 2007 and according to some sources may have even surpassed it. In contrast to the annual minimum, the recovery of sea ice extent during the winter months towards the annual maximum has remained relatively stable over the past decade. The maximum sea ice extent for the years 2007-2011, which usually occurs in March, is around 20 percent below the 1979-1990 average. The Arctic Ocean may be ice free during the late summer months within the next decade or two, but the quick recovery of sea ice during the fall means that ice will continue to cover most of the Arctic Ocean for the rest of the year. Sea ice extent, however, is not the only indicator for the future of Arctic sea ice. The decline of sea ice volume has been even more prominent than the decline of ice extent. For an analysis of ice volume please scroll down.
Arctic Sea Ice Volume (current as of 12/20/2011)
The graph depicts monthly Arctic sea ice volume for 2005-2011 and the monthly averages for 1979-1990 and 1979-2000. The decline of sea ice volume has been most prominent during the months of July-October. In contrast to sea ice extent, however, the decline of sea ice volume over the past decade has been more significant throughout the year. The annual minimum volume usually occurs during the month of September and the lowest monthly average was measured in September 2011. The monthly figure was roughly 70 percent below the average for the period 1979-1990. In contrast to ice extent, ice volume has declined dramatically over the past five years. The 2011 minimum ice volume was more than 50 percent below the minimum ice volume of 2005. Even in comparison to the record low ice extent year of 2007, ice volume decreased by almost 40 percent. The ice extent in 2007 and 2011 were roughly the same with 4.3 and 4.61 million square km, while ice volume decreased from 6.53 to 4.2 thousand cubic km.
The accelerating rate of decline of ice volume may be a more accurate indicator than the rate of decline of ice extent when attempting to predict the time horizon for an ice-free Arctic Ocean. Ice volume data helps to put the recovery of sea ice extent since the 2007 minimum into perspective. Sea ice volume continues to decline rapidly and has occurred at an exponential rate since 1979 according to the PIOMAS graphic to the right. If this trend persists over the coming years we could experience an ice free Arctic Ocean by the summer of 2015.
 Chart created by Malte Humpert with Google Charts based on data from Fetterer, F., K. Knowles, W. Meier, and M. Savoie. 1979-2011. Sea Ice Index. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media. The data can be found here.)
 Chart created by Malte Humpert with Google Charts based on data from PIOMAS Daily Ice Volume Data. Schweiger, A. 2011. Arctic Sea Ice Volume Anomaly, Version 2. Seattle, WA: Polar Science Center, Applied Physics Laboratory, University of Washington. Data set accessed on 12/20/2011 at http://psc.apl.washington.edu/wordpress/research/projects/arctic-sea-ice-volume-anomaly/.