What does this mean?

The maps and bar graphs show the age of Arctic sea ice for each year of a chosen month. On the maps, ice that has survived four years or more appears in the darkest shade of blue, while sea ice under a year old appears in the lightest shade of green. This time series of maps by month shows how the amount and location of each type of ice during a particular month has changed from year to year.

The bar graphs show sea ice age as either millions of square kilometers or as a percentage of the total sea ice extent. On the graphs, ice is broken out into three categories. The bar graphs help show how the proportion of each type of ice has changed during the same time of year, over the satellite record. Continue reading...