As we pass through Spring on the way to summer, the sea ice in the Arctic is starting to melt. The ice usually peaks by the end of the first week in March or so, then slowly declines for a few weeks, then by about mid-May is heading rapidly towards its likely September minimum.
With global warming the ice has been reaching a lower winter maximum, and a much lower summer maximum. This is caused by warm air and water, and it contributes to global warming. The more ice on the sea for longer, during the northern Summer, reflects away a certain amount of sunlight. With less ice, less sunlight is reflected away. This is called a "positive feedback" but it is not a "positive" thing. It is a negative thing. (But it is not a "negative feedback," that's something different!)
We have seen a steady, but mostly recent, decline in sea ice. For years, climate science deniers have been telling us not to worry, the Arctic ice would come back.
But it hasn't, and it is not going to.
The National Snow and Ice Data Center keeps track of the amount of sea ice on the Arctic. They have a nifty tool that you can use to plot the data from 1979 to the most recently available information, which is generally a today or yesterday. I used that tool to make a series of graphics I'd like to share with you here. Read the captions to get the key interpretations. The bottom line: Arctic sea ice reduction has accelerated and is not showing any sign of stabilizing.
I'm reminded of a saying allegedly uttered by thoracic surgeons. The bleeding always stops. Eventually. In a similar vein, I assume the reduction of Arctic sea ice will eventually stop. Then the Dinosaurs can live in the Arctic again!
The chart with no year by year data shown. The grey line is the "baseline" which is usually a 20 or 30 year period against which to measure each year. The grey area is the range over which almost all years occur in this baseline. Since it is two standard deviations that is about 95% of the years within the baseline period. Any year outside of that line is a significant anomaly.
These are the first ten years of available data. Notice that during this period, essentially, the 1980s, all the years are above the average for most of the year.
As we shift to the next ten year period, 1990 to 1999, the total ice cover throughout the year is less, close to the baseline average.
This trend continues in more recent years, with almost all years being below the baseline average. Remember that second graph above where all the years were above average? That shows that the baseline is set during a period of actual warming, so it is an underestimate of how much ice should be there. And now, during the period 2000 - 2009, all the years have much less ice than this.
This is the third year in a row that maximum sea ice has broken a record for being low.
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See also the latest PIOMAS update on Arctic sea ice volume, which provides a better handle on "the amount of sea ice on the Arctic" than extent, even though it's "modeled" rather than "measured":
Facts About the Arctic in April 2017
Volume on March 31st 2017 was 20.398 thousand cubic kilometers. The previous lowest volume for the date was 22.129 thousand km³ in 2011
http://greatwhitecon.info/wp-content/uploads/2017/04/PIOMAS-Volume-2017…
Hypothesis: Authoritarian-controlled minds look to their leadership for guidance on these types of things, and they consider attempts by scientists to simply inform them about the nature of global warming as illegitimate interference with their well managed fear hierarchy.
Jim, that is important information, but the idea that volume provides a better idea of where sea ice than extent is a bit of a falsehood.
The important thing about sea ice is that it covers the sea, providing albedo, habitat, and all that good stuff. The thick is is associated with fast ice, which is an important part of the formation of floating sea ice in the winter. Therefore its deterioration over time is critical and contributes to less surface ice.
Now, the amount of fast ice is so little that it almost doesn't count, and the system has essentially ended. The Arctic will probably always freeze over to some degree. No sun, at the ends of the earth, in the hemispheric winter, but summer ice will be a thing of the past, and it will form slowly and disappear quickly
So, yes, volume is important. But it was never the place where the tire meets the road. Volume is like a measure of how much gas is in your car, surface area a measure of how often you stop at the gas station. If we want to measure how many candy bars we'll sell you at the counter, the latter is the point, the former is a critical variable.
SteveP, interesting idea. May be a bit sophisticated if all they really want to do is punch some hippies.
Also, for the first time in years the Antarctic sea ice is well below historical levels, according to NSIDC. Usually the Antarctic land ice provides enough coolness to produce plentiful sea ice, but not this year.
http://nsidc.org/arcticseaicenews/
Yes, the meaning of Antarctic vs. Arctic is huge. They are two very very different systems and have vastly different influences on climate. The antarctic does not lose significant albedo when sea ice is lacking because there are more glaciers in the southern hemisphere serving that purpose, etc.
The two ends of the earth are polar opposites in more ways than one!
And, yes, over the last year+, the Antarctic has had less ice formation, faster melting, and also, by the way, above freezing surface temperatures in places and times not seen before, so some of the land glaciers that normally only melt at the margins and from the sea itself are now subject to surface melting.
Greg - Sea ice area is obviously the relevant metric if you're considering albedo, but when I studied physics the "amount" of a substance implied "mass" or "volume". That's also the relevant number if you're considering melting of the remaining ice.
Melting 10 meter thick ice takes a lot more energy than melting the same area of 1 meter thick ice!
Jim: absolutely.
Greg, FYI I have just written a paper for a major journal detailing Arctic ice extent and effects on biodiversity. I have some very prominent co-authors on it. I won't let the cat out of the bag yet but as soon as we know its fate you will know about it and like what we have written.
Jeff, I am very curious...
Bernard, you will love this paper. I don't want to blow my own trumpet metaphorically but its really a bombshell, the culmination of over a year's worth of effort. As soon as we get it published, you will know all about it.
This is caused by warm air and water, and it contributes to global warming. The more ice on the sea for longer, during the northern Summer, reflects away a certain amount of sunlight. With less ice, less sunlight is reflected away. This is called a “positive feedback” but it is not a “positive” thing. It is a negative thing. (But it is not a “negative feedback,” that’s something different!)
This is why I think we should use the terms escalating feedback instead of positive feedback and returning / equilibriumising / restorative feedback instead of negative feedback.
Great article, grim reality, here.
This was a very enlightening article and I enjoyed learning about how positive feedback is negative. I had no idea. The ice is melting at a staggering rate and the fact that it has reached a low point in history should make it clear to the nonbelievers that this is real.
It's interesting. Around Barrow, the ice seemed relatively stable last year. I've seen it go out from the shore several times in the last seven years, and sometimes folks will deem it too dangerous to go out on. Elders say the ice is getting progressively thinner, and harder to predict. Last year, the whaling crews were still out on the ice when I left town on May 5th, which seems pretty good. That said, one crew had a lot of trouble getting a big bowhead up on the ice. It kept breaking under the carcass. So, the thinning theme wasn't entirely absent from the ice.
...all very anecdotal of course, but I couldn't help thinking abut these things when I stumbled across this post.
Thanks for the personal story, nonetheless!
Anecdotal stories are always to be taken with healthy scepticism, but at the same time they can be extremely powerful in conveying the reality "on the ground".