The summer just ended in the Arctic and when one speaks of the melting of ice, I think a quick assessment is needed with this new past season in terms of state of the ice. The following summary has been compiled from information from various institutes for the study of snow and ice, including the National Data Centre on Ice and Snow ( National Snow and Ice Data Center ) based in Colorabo the United States.
According to the synthesis of these data, the average amount of sea ice in September (which corresponds to the period of the summer when the Arctic sea ice extent is the least each season) was 5.36 million km ². This corresponds to 1.06 million sq. km more than the worst year yet known what 2007 or 690 000 sq km more than the second lowest year (2008). However, the extent of sea ice in 2009 remains of a 68 million sq km less than the average recorded in September of 1979 (year of early recordings by satellite) to 2000 (see chart below).

Regarding the thickness of the ice, scientists use satellites to estimate the age (which is an indicator of the thickness). This year, the ice so the younger thinner and more vulnerable to melting, accounted for 49% of the total coverage of the ice. The ice two years, a little over 32% against 21% in 2007 and 9% in 2008. In 2009, only 19% of the pack ice was composed of more than two years, which is the lowest since satellite records (see map below).

The trend is the continuing decline in the extent of Arctic sea ice in summer in rates much lower than in 2007 and 2008, but still within the overall average. More alarmingly, this new past summer confirms that there are fewer "old ice". This is replaced by a new thin ice, which is more easily disturbed by wind and water temperature, now higher.