Jenga July 2015

And thus the tradition of the ASIB alliteration of months continues. This one is a bit corny, but kind of appropriate too, so bear with me. Melt Pond May refers to the onset of melt pond formation, and Junction June is about the possible paths the melting season may follow after these two months of preconditioning. The ice pack might remain relatively stable because of a lack of preconditioning, but that balance can still be upset during July, just like a game of Jenga. It has to be an exceptional July, though, and this year's July was exceptional.

To reiterate why preconditioning is important: if the ice pack gets covered by melt ponds early on in the melting season, more solar radiation will be soaked up because melt ponds are much less reflective than ice. That way something which I call melting momentum is built up, a combination of thinned ice and warmer waters on, under and around the ice floes. This momentum can sustain relatively high melting rates, even when weather conditions aren't optimal, as we've seen during the 2011 and 2012 melting seasons. The reverse is also true. Little preconditioning, as happened in the 2013 and 2014 rebound melting seasons, causes trend lines to simply stall at some point, even when weather conditions are conducive to melting.

This melting season didn't undergo any serious preconditioning to speak of. All in all more melt ponds formed on the ice pack than in 2013 or 2014, but it started late and wasn't comparable to years with lots of preconditioning, like 2010 and 2012. It was clear early on that 2015 wouldn't be breaking any records, and the main question seemed to be whether it would end up below 2013 and 2014, or become the third rebound year in a row.

But then July came, and July was hot, as can be seen on this temperature graph made by the NSIDC's Andrew Slater (hat-tip to Chris Reynolds and his latest PIOMAS analysis):

To be able to assess the impact of this relatively high temperature anomaly we need to compare it to other years, in this case the big melters since 2006, and the two recent rebound years. I've divided July up into two halves and here's the first map for July 1st to 15th:

During this first half of July temperatures have been very high in the area north of Greenland and the Canadian Arctic Archipelago, perhaps not as widespread as in 2011 and 2012, but remarkable nonetheless. It's the average sea level pressure that really stands out, though. Except for 2011 no year comes close to the intensity and size of the high pressure area covering Greenland and almost all of the Arctic Ocean. This means that the relatively high temperatures were accompanied by a solar bombardment in those areas where ice is supposed to be thickest.

And this trend continues during the second half of July:

SLP is unequalled in this comparison. In fact the only recent year that came close (for the entire month of July) is 2009, as shown in this comparison I made for the Forum. 2009 is the year that had the largest July volume drop in the 2006-2015 record, with 2015 now being second (see the latest PIOMAS update). And again, also during this second half of July, temperatures have been anomalously high in the Canadian Arctic Archipelago where a lot of the thickest, oldest ice is situated.

Speaking of PIOMAS volume, just today Wipneus posted this animation on the Forum showing how volume loss proceeded during July:

With that much heat and open skies, compactness will invariably take a dive. Remember:

Compactness is calculated by dividing sea ice area numbers with sea ice extent numbers, which gives us a percentage. Short explanation: the Arctic is divided into grid cells. When 15% or more of a grid cell is covered with sea ice it will be counted as 100% covered with ice for extent (meaning the total km2 of the grid cell will be counted for total sea ice extent), whereas the exact amount of km2 that is covered with sea ice will be counted for area. This means that area will always be lower than extent, because of leads or open water within the grid cell.

Here's the thing: melt ponds fool the satellite sensors into thinking that there is open water where there is none. This will get counted for area, but not for extent (unless a melt pond is so big that the 15% threshold is passed). So, if there are a lot of melt ponds, area will go down faster than extent, and the percentage will drop.

Here's the CAPIE graph, wherein I divide Cryopshere Today sea ice area numbers by JAXA (formerly IJIS) sea ice extent numbers:

At the end of July this year's trend line was the second lowest on record, indicating lots of dispersal and melt ponding. But as a matter of fact, Wipneus' compactness graph, using better, more compatible data shows that this year has been lowest - and still is:

And with this we return to the latest melt pond distribution maps that were yet again sent to me by David Schröder from the University of Reading, and are based on his research published last year. Mind you, these maps are model results and don't display the exact locations of melt ponds, but give an idea of how this year compares to record smashing 2012 (left) and rebound year 2014 (middle):

It's clear that according to the model this year has a higher melt pond cover fraction than last year, but 2012 is in a league of its own. Combine this with the compactness numbers, and one might conclude that the low percentage has more to do with ice pack dispersal than melt ponding. This could be correct, as an enormous part of the sea ice pack on the Pacific side of the Arctic has been shred apart in the past few weeks (more on that in a forthcoming article later this weekend).

And so, to return to the introduction of this article, May and June are very important for determining the range of possibilities of an individual melting season. But July can still pull away one block too many, and the whole edifice comes tumbling down, just like in the game of Jenga. This year it won't tumble down as hard as 2012 did, because of the influence the 2014 rebound year has had on the initial sea ice state (see the 2014/2015 Winter analysis) and the lack of preconditioning during May and June, but it will be interesting to see how far this late melting momentum and compaction potential can take the 2015 melting season. It will be difficult to match 2007 and 2011, but it's not entirely impossible either. And then there's the knock-on consequences for volume and multi-year ice.

Either way, July has shown what can happen when temps and sea level pressure are high. Chances of such a July happening is getting greater every year in a warming world (see this article by Robertscribbler to see how heat records are currently being smashed around the world, and what the consequences are). There will come a year where the initial sea ice state is worse than this year, followed by above average preconditioning. Then add a July such as this one, and you have a recipe for near ice-free conditions come September. To think that this process is not going to affect anything or anyone, is even worse than not thinking at all.

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I'd like to thank David Schröder and all his co-authors for taking the time and effort to provide me with their model results. It has been a huge help in assessing the direction this melting season has been taking.

Comments

[G man]

Interesting. The early July spike would seem to correlate well to the sudden onset of the very slow beginning to Greenlands melt season. On the flip side the late July temps have seen Greenlands melt come to very early end.

[Neven]

There's a fantastic segment on the Arctic Sea Ice Forum for discussing Greenland and its glaciers, with people presenting all kinds of analysis and satellite images. Really top quality stuff.

The same goes for the Antarctica segment.

Information is everything.

[Phil]

Hi Neven,
Purely out of interest for your alliteration, 'Jenga' is swahili for build, and build with an exclamation mark - Jenga! Build!
I found this out when a couple of years ago I delivered a skills development for Protected Area Managers at a research station in Kenya called Mpala, and stayed in a house called Jenga, which was built with funds donated by the woman who invented and marketed the game. She used to live nearby.
Thank for all your work:)
Phil

[Neven]

Thanks, Phil. I wouldn't be able to sleep in a house called Jenga. Just imagine someone pulling out the wrong piece of wood. ;-)

[Phil]

Very good :) :)

[RunInCircles]

I have been watching the north pole web cams for a few years. My memory tells me that the melt ponds always start freezing over by the last week in July or the first week in August. Does anybody else remember it this way? How many think that the block of ice just north of Alaska will still be there at the end of this melt season?

[Jim Hunt]

A couple of yachts have now managed to make it through the Bellot Strait on the southern route through the Northwest Passage:

http://GreatWhiteCon.info/2015/08/is-the-northwest-passage-open-yet/

Here's an animation of a satellite's view of what's been happening to the sea ice in the vicinity over the summer of 2015:

http://youtu.be/sZtQ8XDxBAI

[Jim Hunt]

RunInCircles,

Perhaps your memory is faulty? I seem to recall "north pole web cams" (which of course aren't anywhere near the North Pole by then!) falling over into the melting ice by the end of July 2011:

http://youtu.be/h1Xc0rUtJ4A

Here's the view from another one at the end of July 2013:

Click the image for the bigger picture.

[G man]

Well it looks like the melt will shut down very soon with winds howling up Baffin Bay and Northward up the Fram. Also with winds in the Arctic central H-pressure almost forming a wall of wind slamming the ice cap up against the Canadian Archipelago stopping any escape through the Fram. And temps according DMI are about to go below freezing anyday now.

http://earth.nullschool.net/#current/wind/surface/level/overlay=mean_sea_level_pressure/orthographic=-48.34,85.94,497

[jdallen_wa]

With respect, G-man, temps won't be far enough below zero, and, there is still an awful lot of energy still present and *entering* the Arctic such that momentum will continue for several more weeks.

Also, don't underestimate the influence of moisture being carried along as well. It is premature to predict an end to the melt.

I will note on the forums, weather like this was noted at the end of July, and someone predicted a "sharp slowdown". The next week following saw something 600,000 KM2 of melt, iirc.

I don't expect that here, but I'd caution you against making broad vaguely supported assertions.