Time to think in 3D about Arctic sea ice
The recent rash of news alerts about the all-time-low, end of summer, Arctic sea ice extent has certainly given new food for thought about the state of the climate. Of course we shouldn’t be entirely surprised by this state of affairs as more rapid warming at the poles was anticipated long before the issue of rising emissions became a reality that we would have to deal with.
Back in 1895, Svante Arrhenius came to the conclusion that “temperature of the Arctic regions would rise about 8 degrees or 9 degrees Celsius, if the carbonic acid increased 2.5 to 3 times its present value”. Fortunately we haven’t reached this level of atmospheric CO2 or warming just yet, but nevertheless the message was there 120 years ago.
So it was timely to be able to hear from a current expert on the subject of the Arctic at the 34th MIT Global Change Forum held in Canada last week. The speaker was Professor Louis Fortier, Scientific Director, ArcticNet, Université Laval. Somewhat depressingly, the news was worse than the already worrying news of that week, shown above.
Firstly, Professor Fortier showed how climate models verified the findings of Arrhenius. In a 2070 world with CO2 at 550 ppm, warming in the Arctic is seen to be 5°C, compared to 2-3°C in lower latitudes.
But the really alarming news came when the discussion moved from 2D to 3D. Although we think of floating ice in the 2D context, it does have some thickness. This is caused by the buildup of ice from year to year, starting with ice that survives the previous summer melt which then increases in thickness during the winter. Thirty years ago, “old ice” (layers in the pack some 5-10 years old) made up some 50% of the floating pack at the end of the summer melt. Today, there is almost none of this remaining, with the ice at the end of summer consisting of the thin remnants of the winter freeze.
The 2D view shows that September ice extent has declined by about 50% since 1980.
But the 3D view which incorporates the measurements of ice thickness shows an even more worrying trend. Ice volume has declined by 82% since 1980.