This animation shows a 3-year moving average of minimum sea ice concentration for from 1979-1981 through 2003-2005. Average climatology from 1979 to 2004 which is shown as a yellow outline is also included. This line represents the average location of the edge of perennial sea ice cover.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 188.8.131.52.0