Mark Cochrane
Another year of low ice cover in the Arctic. So what’s new? Few know about this and fewer care. The decline has been going on so long that we fail to be shocked anymore. In the graph below the gray area is where 95% of years should fall. We are well below that area, yet again, about where we were last year. The dashed line is 2012 when we experienced the lowest sea ice cover (in September). Depending on the vagaries of the weather, this year may or may not be the lowest on record but just looking at the area of cover is misleading, since it tells you nothing about the thickness of the ice.
As the ice cover expands in the cold Arctic winter it covers the ocean and traps the heat it contains. This allows the air temperatures to drop very low above the ice. Think of the ice as the covers on your bed. If your covers are thick your body heat stays contained even on a cold night. If you have just a thin sheet you don’t stay quite so comfortable.
In the Arctic, sea ice gets thicker the older it gets as it goes through successive winters. As recently as the 80s, 30% or more of the ice cover was 5+ years old and first year ice was not much different at about 35% of the area. Now, older ice area has been reduced to <5% while first year ice makes up nearly 70% of the area.
Thin ice breaks easier during Arctic storms and, much like crushed ice in your drinks, melts faster. Open water in the Arctic summer enjoys 24 hours a day of sunlight. Ice reflects most of the heat, but open water absorbs almost all of it. This makes the Arctic ocean warm more and more year after year, which in turn makes the formation of new ice in teh winter harder and harder until later in the year, after enough heat escapes the surface waters. That heat plays havoc with the regional weather in the Arctic. The Polar Vortex is weaker and slower to form making it more likely that cold Arctic air will spill out in bursts across North America and Europe.
The ‘death spiral’ map shows how sea ice volume is circling the drain that will one day, in the not too distant future, end with an ice-free Arctic summer. How much ice have we lost in the last 4 decades? Comparing April 2017 to April 1979, the reduced volume of Arctic sea ice would be nearly enough to cover the entire combined land area of both Canada and the United States with 1 meter of solid ice.
Alas, the only thing poorer than the human race’s ability to understand the exponential function and large numbers is its grasp of geography…
Mark
Damn the Matrix 
Two very interesting Science Shows recently on climate change :-
http://www.abc.net.au/radionational/programs/scienceshow/has-‘denying’-won/8618606
http://www.abc.net.au/radionational/programs/scienceshow/ominous-signs-for-larson-c-ice-shelf/8604862
I heard that one……. one nutjob denier actually said (and I’m paraphrasing) why should we bother spending money on ‘fixing’ climate change for future generations when they will be far wealthier than us……
Perhaps more relevant to most people – who will never go to the Arctic – is that other part of the world where climate change is accentuated. i.e. the tops of our mountains. Plenty of research has been conducted on declining snow in Australia.
In brief: Australia doesn’t have very high mountains. The snow line of Australian mountains is gong upward phenomenally – at the rate of 20 metres per year. By 2050 science predicts that no Australian mountains will receive a consolidated bed of snow. Tasmania’s contains are 300 metres lower than Victoria’s. Tasmania’s ski resorts have basically had the biscuit already. The tows lie idle doing most of our Winters. Ski enthusiasts have been trying to artificially extend skiing by conducting slope grooming (removal of rocks) so that skiing can still happen when there is very sparse snow cover.
In future bigger Australian ski resorts, such as Thredbo, will have to reply on manufactured snow. This is not able for smaller resorts.
Most Tasmanian skiers from the 1980s no longer ski. Or they fly to NZ to enjoy their higher mountains. Back then there was a strong Tasmanian community of cross country skiers, relying on the Central Plateau being plastered by late Winter. Most of their skis are now sitting in the Tip Shops.
I’m not a skier, but I like to raise this issue of snow because this is the one area where climate change is not something that is predicted to happen in the future. Yes folks, it is already past tense.
Talk to any older Tasmanian and they will let you know about the snow we used to get. Talk to the Hobart Council which has had the job of ploughing the Mt Wellington (kuanyi) pinnacle road for the past 100 years. Talk to the Hydro and they know (but won’t talk publicly) about how they used to benefit from the megalitres of buffered water storage that used to be held on Tasmania’s mountain tops, to feed into the hydro dams during mid-Spring melt.
The mechanics are simple to understand. Once you get a bed of snow that stays there, the snow itself is reflective, and this reflects the runs rays. More snow means that more snow builds up. Below a critical temperature level and the dark mountain rocks stay exposed to the Winter sun and absorb enough heat so that any light snow falls melt before the next front comes by. This is why our alpine areas are being affected by climate change much more than are lowland areas.
From my childhood in New Mexico USA, I understood that going up-mountain was similar to going toward the pole in latitude but staying at the same altitude. Consequently, the polar amplification that is commonly spoken about in global warming is very similar to the up-mountain amplification that you have described so well.