Sea ice in the Arctic ocean declines from its near-maximum state in early spring 2011 through the summer and up until the summer minimum of Sept. 9, 2011, in this visualization of data collected by the AMSR-E instrument on NASA's Aqua satellite. Sea ice goes through this shrink-and-swell rhythm every year, but since consistent satellite observations began in 1979, both the annual minimum at the end of summer and the annual maximum at the end of winter continue to decline in area and thickness.
Arctic sea ice extent on Sept. 9 was 4.33 million square kilometers (1.67 million square miles), placing 2011 as the second lowest minimum ice extent on record. Ice extent was 2.43 million square kilometers (938,000 square miles) below the 1979 to 2000 average.
Below two versions of the AMSR-E visualization is a video featuring NASA Cryosphere Program Manager Tom Wagner, who shares his insights on the 2011 minimum.
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 220.127.116.11.0