On Thin Arctic Sea Ice

The Arctic sea ice volume chart shows the rapid decline in the volume of Arctic sea ice:

The Arctic sea ice area chart shows the area decreasing but less precipitously:

(This chart includes a best-fit line through the September data with a non-linear projection to hit zero when the best-fit line through the sea-ice volume data hits zero)

This means that the diminishing area of sea ice is also becoming progressively thinner, as shown on this chart of mean thickness, calculated as volume divided by area:

Notably, when data-recording began in 1979, the sea ice was at its thickest in September. This sounds a bit counter-intuitive: it means that, although there is not much sea ice left, only the thicker ice had survived the Arctic summer. Now September is one of the months with the thinnest sea ice. This demonstrates the progressive loss of thicker multi-year ice, which used to survive well through the Arctic summer, while the single-year ice melts away, but not any more.

The low average thickness in December, January and February is explained by the vast area that becomes covered by thin single-year ice as the extreme cold draws in each Arctic winter.