August 4th 2013
"As the weather is switching again, things will probably slow down." That's what I wrote two weeks ago for the conclusion of ASI 2013 update 5, and never has a greater understatement been made. At least not on this blog.
The weather did switch from an ideal set-up for ice decrease (causing one of the most rapid decreases on record) to a situation that is next best for ice decrease, with a fierce, but short storm at its heart, finally followed by the neither-fish-nor-flesh set-up where weather is fickle in the Arctic and never really settles on a stable pattern that can deepen to one of the other two states.
This almost always slows down ice decrease, and I say 'almost' because last year it didn't. Frankly, I was expecting it wouldn't have as much of an impact as it did in the past two weeks, because we started the year out with a record amount of first-year ice. And despite (or because of) the slow start to the melting season the melting potential is huge.
But huge or no huge, the impact of the weather has been huge as well. In fact, it's so big that I'm starting to doubt my eyes.
Sea ice area (SIA)
I don't know what is going on over at Cryosphere Today, but the melting has come to a complete standstill. In the past 10 days the ice pack has not lost, but gained 20K km2! That's so crazy for this phase of the melting season that I barely have words for it. It's unique as far as the record goes.
Here are the graphs for this month and the previous one:
2013 is now above all other years, except for 2005 and 2006. Again, it doesn't seem to make sense, given the amount of first-year ice and the fact that ice loss was so rapid in preceding weeks. The only explanation that makes sense to me (which I saw on the ASIF), is that the clear skies during those 10 days of weather conducive to ice loss caused a lot of melt ponds, which are now freezing over again because of the cyclonic conditions.
But how long can that be kept up? There's still 5-6 weeks to go until the end of the melting season, but 2013 is trailing 2012 by over 1.2 million km2. A new record has become impossible for all practical purposes.
Here's the link to my updated CT SIA spreadsheet.
The complete standstill stands out clearly on Jim Pettit's SIA graph:
Sea ice extent (SIE)
The slowdown is much more spread out on the IJIS graph. It announced itself earlier than in the CT SIA data and has gone up steadily, joining the cluster of slower melting seasons:
Here's the link to my updated IJIS SIE spreadsheet.
Cryosphere Today area per IJIS extent (CAPIE)
Now, here's where it gets interesting. Because CT SIA has plateaued so radically, and IJIS has continued to go down, albeit at a slow rate, the result of dividing one by the other has been that our CAPIE index has shot up dramatically:
For a thorough explanation of what CAPIE is, read the CAPIE subsection in this ASI update.
This year is almost 14% more compact than 2012! This can't be due to convergence of the ice pack because of the cyclones we have had so far, which caused a lot of divergence, pushed the ice floes away from each other, creating holes within the ice pack. So again, the only possible reason I can come up with is freezing melt ponds, perhaps combined with ice floes falling apart in small pieces that spread apart, but don't melt out just yet. But even if that were the case, that still would't explain it.
This is crazy. :-)
Regional SIE and SIA
Regional graph of the week, taken from the Regional Graphs page:
The Beaufort Sea also was a good candidate for this update's entry, but the East Siberian Sea (ESS) was perhaps a tad more spectacular, as can be seen on this map that Wipneus has custom-made for this ASI update, showing the differences that have taken place since the previous ASI update. Red = ice two weeks ago, open water now; blue the other way around:
The ESS has been behind the curve for all of the melting season, but is playing catch-up now and will soon be completely empty of ice. When the stubborn piece of fast ice west of Severnaya Zemlya comes loose - and it is disintegrating as we speak - the Northern Sea Route will be officially open again from one end to the other.
The ice in the Northwest Passage is also melting fast in situ, but the western entrance of the main route could remain blocked by multi-year ice. We'll see how that plays out, with some interesting weather coming up.
Sea Level Pressure (SLP)
The two-week animation of Danish Meteorological Institute SLP images shows what has been going on weather-wise:
We see the big cyclone (reaching a lowest core pressure of 977 hPa) come into being and dissipate fast, followed by that set-up where neither high-pressure systems do major damage to the ice pack with their clear skies, or persistent cyclones with their winds. Apparently it has been enough to cause that major slowdown, or even standstill on some graphs. I'm amazed.
And I'm also amazed when I see what the ECMWF model has in store for the Arctic. Check out the 6-day weather forecast (click for a larger version):
Okay, so we have high-pressure systems taking over the Canadian Archipelago and Greenland, with a sort of a Dipole system setting up, but the low-pressure system on the Siberian side of the Arctic grows into another big sub-980 hPa cyclone? You have got to be kidding me...
Here's a close-up of the forecast for Thursday:
If 2012 was the 'year of the cyclone', 2013 is more and more turning into the' year of the cyclones' (plural). I don't know what to say about this right now, but I'm sure we'll discuss it in weeks to come. This is one strange melting season.
It's still pretty warm in a large part of Siberia, causing numerous wildfires and broken records (see for instance here), and Alaska seems to be baking again as well. Over the Arctic Ocean it's back to anomalous cold again:
The Siberian heat is also very pronounced on the DMI SST anomaly map, where temps in the Barentsz and Kara Seas seems to have gone up some more, with other zones staying more or less the same compared to two weeks ago:
Just a meagre 7-10 days of weather conducive to melt, compaction and transport of Arctic sea ice, is what the Arctic saw at the peak of the melting season, but still the 2013 trend line was well on its way to catch up with the big melters on most graphs. The last two weeks changed all that.
The change is actually so radical that I can see two possible conclusions:
1) The sensors are still having a very tough time making sense of what's going on below, due to enhanced cloudiness and the structural properties of the ice pack's weak parts. And so, under the right conditions, we could be seeing an above average melt in August.
2) A slow start to the melting season kills all momentum for the remainder of the melting season, which would go a long way in explaining the fact that total ice kept decreasing in 2012 when the weather switched, and this year it didn't.
That's all fine and dandy, but of course the melting season is far from over yet. I've been expecting that melting potential to come to full fruition for weeks now - and saw some of it in those few weeks in July - but even with some more freaky weather coming up, I don't know what to expect any longer. This melting season is completely draining me, making me feel like I don't know anything.
Like I've been saying for weeks now a new record is a very difficult proposition. But even ending below 2007, 2010 and 2011 will be quite a feat, and that's something I didn't expect. At least not like this. I've seen slowdowns before, but this is out of this world.
We'll know more (hopefully) in two weeks.