Long term data records from SONAR aboard submarines acquired during 1958-1976 and 1993-1997 show a reduction in summer sea ice thickness by 1.3 meters (Rothrock et al., 1999). Using NASA's Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, it has been determined that Arctic mean sea ice thickness reduced from 3.64 meters to 1.89 meters between 1980 and 2008. This is a total decrease of 1.75 meters in two decades (Figure 1). According to IPCC (2007), results based on SONAR and physical sea ice models suggest a decrease of approximately 1 meter in Arctic sea ice thickness between 1980 and 2000. Although, a majority of studies show a decline in Arctic Sea ice thickness, many others present the contrast. The sea ice thickness measurements along the Siberian and Canadian coasts do not show any significant changes.
Information provided by Dr. John Yackel (Cryospheric Climate Research Group, University of Calgary)