Well, Arctic sea ice made the headlines again this week, as a new study has confirmed what some climate models have been predicting about the amount of it. When you hear discussions about summer melt season ice loss in the Arctic, they are talking about ice extent — that is, how much the surface area of ice has either melted or changed compared to the average. In September 2012 the Arctic hit an all-time low for ice extent. This all-time record low meant about half of the surface usually covered in ice during the summer has disappeared compared to the 1979-2000 average.
While ice extent is a relative easy way to see how much ice loss occurs, it is really not the best measurement to use. What we need to know is how much ice volume there is. Ice extent considers just the surface area of the ice; ice volume also looks at how deep or thick the ice is. Determining ice volume is much more difficult compared to ice extent and up to 2010 there wasn’t really any reliable, easy way to measure volume, so Arctic ice volumes were estimated using the University of Washington’s PIOMAS model (Pan-Arctic Ice Modelling and Assimilation System). This model suggested the volume of Arctic sea ice loss may be approaching 75 to 80 per cent, which is a rather shocking number. A lot of people, especially climate change skeptics, pointed to this model as being unrealistic and thus another reason why we should not believe anything being reported about Arctic ice conditions.
In 2010 a new satellite, CryoSat-2, was launched by the European Space Agency, bouncing microwave energy off the ice to measure its thickness. It is able to determine the thickness because the beam bounces off both the top of the ice and the water below the ice. The difference in the timing of these two bounced beams allows scientists to measure the ice thickness. After two years of collecting data and then analyzing and validating it by comparing the satellite measurements to actual ground — or rather, ice — measurements, it appears the estimations of 75 to 80 per cent ice volume loss were very close indeed!
In 1979, ice measurements estimated the total amount of Arctic sea ice during the summer minimum as around 17,000 cubic kilometres. The latest numbers from 2012 show summer minimum volume had dropped to an astonishing low of around 3,300 cubic km. That works out to an 81 per cent decline in ice volume. In an article published on the Think Progress website, author Joe Romm describes these results with the headline “Arctic Death Spiral Bombshell: CryoSat-2 Confirms Sea Ice Volume Has Collapsed.” If you wonder why they call it a death spiral, just check out the accompanying graphic that shows the loss of ice for each month of the year over time. You can see how the lines are slowly spiralling in toward the zero ice-over in the centre.
The article goes on to state this story should be the story of the day, month, year and decade. It is now estimated that instead of seeing a mostly ice-free summer Arctic by 2050, we will likely see it within the next 10 years, and that it is almost certainly too late to make any changes that will stop it from happening. What the outcome of this will be is still uncertain, but most climate and weather scientists agree it will definitely result in a permanent change in weather patterns across the Northern Hemisphere.
We talked in the last issue about how the loss of Arctic ice appears to be affecting the jet stream, causing it to become more meridional. Just what will happen when all the summer ice is gone is anyone’s guess, but I don’t think it is crying wolf to say we’ll see significant changes to our general weather patterns.