I expected Alun Anderson’s After the Ice: Life, Death, and Geopolitics in the New Arctic to mostly contain information I had seen elsewhere. In fact, it is chock full of novel and interesting details on everything from marine food webs to international law to oil field development plans. I read the first 200 pages in one sitting.
One chapter goes to some length in describing how we know what we do about Arctic sea ice volume. It is harder to measure than the extent of sea ice, which can be observed in all sorts of ways by satellites (optical instruments, synthetic aperture RADAR, passive microwave emissions, etc). One effort to estimate how ice volume is changing was based on multibeam SONAR on submarines. An 11 day survey conducted by Peter Wadhams, using the nuclear-powered HMS Tireless concluded that 40% of Arctic sea ice has been lost since the 1970s. Another team, led by Drew Rothrock, used previously secret US submarine data to confirm that figure for all areas that submarines have been visiting.
Anderson also describes the importance of the cold halocline layer: a thin layer of cold water that insulates the bottom of Arctic ice from the warmer Atlantic waters underneath. Without this layer, multiyear Arctic ice would be doomed. For a number of reasons, climate change threatens to undermine it. If it does, the complete disappearance of summer sea ice could occur faster than anyone now expects.
There are many reasons to worry about the vanishing Arctic ice, from the increased absorption of solar radiation that accompanies lost albedo to the danger of invasive species entering the Atlantic from the Pacific. I’ve written previously about ‘rotten’ ice, and many other issues in Arctic science.