Earlier in the northern summer, it looked like the rapid melt of Arctic Sea ice we've been seeing over the last several years was happening again, but rather than being a record year, it was merely tracking along the lower side of the distribution of the long term average. Last year, in contrast, the amount of sea ice hit an all time low early in the year and then broke previous records into tiny icy pieces.
One of the reasons last year's ice melt was so dramatic is that an early storm churned up the ice and got melting going a bit early.
This year, there was no early churning up event, but over the last several days of June and beginning of July, the rate of sea ice melt has suddenly increased dramatically and this year's track is looking like it may come close to catching up to the previous year's unprecedented extreme.
To give you an idea, I've got three figures I made by taking screen shots from the Chartic Interactive Sea Ice Graph (here).
This interactive chart uses the high quality data from 1979 to the present to produce a spread (the gray area) showing the range of ice at two standard deviations. Here, I've plotted the first ten years of that period against the standard deviation (and mean) to show that during the first part of the period in question the sea ice was melting less each year than the entire spread.
The second figure shows the same thing but for ten years near the end of this period, not including last year and this year:
This shows how the standard deviation spread is actually a bit misleading on its own because it does not show the trend of change over time, but this comparison of an earlier ten year period and a recent ten year period demonstrates it dramatically.
Now, have a look at the third graphic, showing last year's dramatic sea ice drop and the track for the current year so far.
The melting of this ice faster and more completely means there will be more warming of the Arctic sea by sunlight; the ice would reflect more sunlight back into space but open water absorbs more of it. So, the Arctic is warmer than it should be and it is getting warmer than it was, at the same time.
The warming of the Arctic in turn reduces the gradient of heat from the equatorial regions to the poles in the Northern Hemisphere. This causes the Jet Streams do do strange things, which causes Weather Weirding, the non-technical term we apply to ... well, to weird weather. You can read about this link in the following two posts:
Of course, extent is only part of the issue as the ice is becoming thinner which means that total mass is dropping dramatically.
See http://climatecrocks.com/2013/04/23/arctic-ice-mass-loss-visualized/ for a great visual presentation of the ice mass loss.
Greg: Arctic temperatures have been below average since the melt season started in late March/early April.
Antarctic ice has been above average for the last year. Global ice extent was just above average, but has since fallne to near average.
Antarctic and arctic usually march in inverse link-step. When one increases, the other decreases.
Les, your first statement is very misleading. Arctic temps in the middle of the melt season never go very high. What is important is the length of time over which temps are warm, and before and after the maximum. It's like looking at a marathon runner, and estimating the total race time on the basis of the occasional sprint.
Antarctic ice and arctic ice are not in inverse link-step (if that's even a thing). They are under very different regimes. You made that up.
My question for you is this: What are you getting out of making stuff up and pretending that climate change is not real?
Some inconvenient facts in the last 3 posts I have responded to, Greg?
Les, you've been posting cherry picked data and untruths for a lot more than three comments, and some time ago you violated my comment policy, which is here: http://scienceblogs.com/gregladen/about/#nefarious
I would love it if you showed my what was untrue in the references I post.
And, I checked. I have not violated any site policies.
I've shown you in a number of spots.
You checked? With whom?
Let me be clear: My policies are entirely arbitrary and capricious. I can do whatever I want. I happen to articulate some guidelines (and I gave you a link to that) but those are just guidelines. There are no policies that you can "check with" and make an argument that I have to do something different. That's you being very strange.
"Antarctic ice and arctic ice are not in inverse link-step"
Sure they are - whenever it's summer up here and the ice melts, it's winter down there and the ice grows. And every year, people claim that expanding Antarctic ice means there's no global warming. Can someone find a Stark to explain the mechanism to Les?
What you might have asked Les, by the way, is if Arctic temperatures this melt season have really been "below average" (compared to what time range?), then isn't it quite alarming that the decrease in ice cover has been faster than average? Doesn't that imply that something else is going on, like say the ocean itself heating up?
I don't think Les was talking about seasons. And yes, the arctic ice is currently at close to the second lowest level and on track to equal or exceed last year's record breaking melt!
Are there equivalent charts for thickness? We have scattered information since the late fifties when US and USSR subs started making crossings. The ice is getting thinner, but by how much and for how long should be an important variable. Areas that don't clear off, becoming easily measurable by satellite pictures, have still been losing ice. The rapid collapse we're seeing now has to be partly because of a decades long thinning. The eastern Arctic is behaving more like North Atlantic sea ice than true pack ice.
The thought that's forming in my head as I write this is that we've been invisibly losing thousands of cubic miles of ice every year without a clear measurement of that fact (unless you know of one). Those thousands of cubic miles of cold water would have had a dampening effect on global warming. But as we run out of ice not only will the changed albedo of the North become a problem, but one of our air conditioners will be turned off.
Please tell me this has already been factored into the climate models.
Its been factored in. You are right, the thickness is even more important and I'm planning a post on that soon. Here's an example of a graph showing thickness and volume:
The thick ice tends to form an anchor for the new ice each year, so when there is less thick ice, that also slows reformation, which probably translates around the annual cycle to faster remelting.
That makes me feel a little better.
The fact that willing tools like Les still exist temper that a bit, but I'll take what I can get.
I like having Les around. He makes me feel much smarter by comparison.
Why are there no chemical engineers looking at all this. Looking at extent of ice, thickness of ice, water temperature and air temperature and albedo. You need to be looking at heat flow then it will all make sense. If that ice is going to disappear then you need to provide so many Kilo Joules of heat. If the sun (modified by adsorption) and the heat in the warm current flows provide the required amount then we get water. If not it stays as ice. Can't someone amongst all these climatologists do the model properly please. And in case you ask It is a young man's game and I am yesterday's generation.
There are chemical engineers looking at this and the physics and chemistry are well understood, young man!
I'm with Roger Caws in treating the whole thing as energy balance. What I don't get is the relevance of sea ice extent. If 16% of the sea is covered in ice, 84% is absorbing sunlight. If the ice is spread out evenly, according to NSIDC it's 100% extent. If 14% of the sea area is covered with ice but spread evenly with the rest of the ice clumped together, it's 2% extent. Same ice area, same volume, same 84% absorbing the suns rays. The only things I can think of are the local weather may change, and clumping may change local ice thickness.
The PIOMAS volume anomaly graph http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ic… for the last couple of years appears to show volume recovery in the winter, i.e. heat entering Arctic in summer is balanced by heat leaving in the following winter. I would expect a dark Arctic sea to be covered with at least thin ice in winter. However, the amount of heat entering in successive summers appears to be increasing. OK, so it's only three summers but if the trend continues I suspect that when an area is totally ice-free, the heat will still be coming in, so temperatures may rise rapidly. A fly in the ointment is pan evaporation demonstrates that solar radiation is a major factor in evaporation, so heat will be lost to the atmosphere. This may then condense on the Greenland ice sheet.
I'm tired and I'm waffling. Apologies.