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September 22nd 2012
I left for a vacation after all the records had been broken and have returned just in time to see all the minimums get hit on the various graphs. In the past couple of years the National Snow and Ice Data Centre in Boulder, Colorado, has built up a well-deserved reputation of being the number one source of information when it comes to Arctic sea ice. When they called the minimum three days ago, it was picked up far and wide by news agencies around the world, an even better response than when all the records started to break one by one a little over a month ago.
I remember well the excitement I felt around this time in 2010 and 2011, checking all the graphs and satellite images every hour, trying to predict when the melting season would end. But none of that this year. Maybe it's because I still feel overworked, despite my vacation. Maybe it's because the records were broken so early in the season, preceded by several spectacular events. Maybe it's because this melting season was so freakish that it was practically impossible to pinpoint the minimum a few days in advance.
All those factors play a role, but what I think is going on, is that this stunning melting season has made me even more acutely aware of the gravity of what is taking place. This melting season has provided the final and definite confirmation that the ice is thin, PIOMAS has it largely right, and I have a very hard time finding indications that this is going to turn around real soon. To be able to watch and write about the Arctic sea ice, I used to block out the realisation of risks, so that I could make a joke here and there and be scientifically reticent in my own amateur way, keeping up appearances, acting objective.
But my bubble has burst. I'm already watching past the minimum. As the melting season ends, it feels as if things are only beginning. The age of consequences.
Sea ice extent (SIE)
Now that AMSR2 is operational, IJIS doesn't seem to revise the last data point, so I'm including it for this latest graph:
On September 16th the trend line shortly dipped below 3.5 million km2, reaching a minimum extent of 3.489.063 square kilometres. That's more than three quarters of a million below the 2007 record, and more than a million below 2011. I knew that there was a good chance the record would be broken this year, but never imagined it would be by such a large margin. Especially not with circumstances that in many ways were the opposite of those in 2007.
The current difference between 2012 and other years is as follows:
- 2005: -1,551K (-15,967)
- 2006: -2,083K (-6,049)
- 2007: -520K (-15,357)
- 2008: -1,009K (-12,195)
- 2009: -1,637K (-2,158)
- 2010: -1,151K (-19,717)
- 2011: -982K (+156)
Sea ice area (SIA)
Cryosphere Today sea ice area has also bottomed out, a couple of days later than in the previous 5 years, which is slightly surprising, as the ice pack was much smaller and thus the ice edge much further North. One would expect darkness and freezing temperatures to cause the minimum to occur a bit earlier. But the Arctic doesn't give a rat's ass about expectations.
This year's trend line dove almost 700K below the previous record lows of 2007 and 2011, reaching a minimum area of 2.234.010 square kilometres. Considering the fact that sea ice area at the end of the melting season is a very decent metric (melt ponds having frozen over or emptied due to fracturing) the 1 million km2 threshold is coming awfully close.
Jim Pettit sent me some more of his excellent stat-facts:
- Area bottomed out this year at 2,234,010 km2. That’s 670,730 km2 below the previous record low set just last year.
- As of yesterday, 2012 area has been below last year’s record (and 2007’s, too) for 33 consecutive days.
- Since the area maximum was reached back in March, area has dropped by 11,474,501 km2. That’s an area 16.5 times larger than Texas, or 6.5 times larger than Alaska.
- 83.7% of the ice area present at maximum disappeared this year. That’s the most ever, easily beating 2nd place 2008, which lost 78.38% of its maximum area. (http://iwantsomeproof.com/extimg/sia_9.png)
- As of yesterday, 2012 area had been the lowest ever for that particular date for 83 consecutive days (since June 30), 99 of the last 104 days, and 111 days overall.
- The area negative anomaly has been greater than 2 million km2 for the past 50 consecutive days. (That’s nearly half--47.2%--of all the days in the satellite record with a negative anomaly equal to or greater than 2 million.)
- This stat doesn’t seem to impress or even interest anyone beside me, but I think it’s pretty telling anyway: until this year, area had never fallen below half of the daily average. It’s now done so 17 of the past 18 days.
The thing to look out for now, is the CT SIA anomaly and whether it will go below the record of -2.635 million km2 that was reached on October 19th 2007. It's close, but might take a while longer if refreeze is rapid:The current difference between 2012 and the other years is as follows:
- 2005: -1,921K (+10,244)
- 2006: -1,778K (-7,447)
- 2007: -616K (-8,666)
- 2008: -704K (-7,583)
- 2009: -1,386K (+9,485)
- 2010: -922K (+1,916)
- 2011: -882K (+9,275)
Between brackets is the average daily area de/increase for the first 19 days of September. 2012's average daily area decrease for those 19 days is -7,610 square km per day.
Cryosphere Today area per IJIS extent (CAPIE)
CAPIE tells us something about the compactness of the ice pack. In this phase of the melting season, a low percentage basically tells us that the ice pack is spread out a lot. When the CAPIE trend line shoots up, compaction is going on. See this blog post for everything you want to know about this measurement we devised ourselves at the ASI blog.
Here's the graph:
As you can see, 2012 is lowest of all years since 2005. This means that the pack is more spread out than in those years (also explaining the rapid climbing of IJIS extent number we're seeing in the past couple of days). Imagine what would have happened with compacting winds, like were seen in 2007 (light blue line). SIE and SIA would probably have been even lower.
Regional SIE and SIA
Regional graph of the week:
There it is again, the Cryosphere Today Arctic Basin SIA graph, showing the amount of sea ice area in this region for the last 33 years. Although the short-term graph - showing this year and last year - is showing an uptick due to all that open water north of 80 degrees latitude that is starting to freeze and close, I wanted to show the long-term regional graph one last time.
There was talk of a plateau since 2007. This no longer holds. The question for the next 2-3 years: Will Arctic Basin SIA return to that plateau? Is this year the start of a new plateau? Will it go even lower?
Sea Level Pressure (SLP)
Let's have a look at the animation of Danish Meteorological Institute SLP images since the start of this month to get an idea of what happened:
That big high over the Siberian Seas that formed around the 8th of September would normally have been end of season in 2010 and 2011. I can't get rid of the impression that this year didn't respond as fast to that SLP configuration, despite the fact that the ice edge was very close to the cold North Pole.
High pressure means open skies, and as the ice pack is getting darker and darker, there's a lot of heat radiating away, cooling the water down, causing it to freeze. Let's see what the 6-day weather forecast by the ECMWF model has in store:
I'm seeing mostly low pressure systems dominating the central Arctic (and another big one bothering Alaska). Low pressure means cloudiness, and clouds trap the heat, so in theory we should see a moderate re-freeze. On the other hand: the ice pack is so small, and there are so many dispersed ice floes on the edges and within the ice pack itself, that I wouldn't bet on a slow re-freeze just yet.
Air temperature above 80N has finally started to go down, but look how far above the average it still is (compare to other years at DMI):
Red and orange has been a feature on the DMI SST anomaly maps practically all summer, but things look much better than on the image from ASI update 10:
Things still look relatively hot in the three B's: Baffin Bay, Beaufort Sea and Barentsz/Kara Sea. We will keep an eye on how this plays out this winter, as it happens to be the most important thing to be looking out for.
The melting season has come to an end, but where in previous years this meant hibernation time, I fear this freezing season could have some events in store that will make dozing off more difficult. There is a lot of interesting research into the effects of disappearing sea ice on weather patterns that will be put to the test again this winter.
And what happens this winter, especially with regards to ice volume, will have a major influence on next year's melting season. If volume keeps dropping we will almost certainly see another melting season where sea ice extent and area will just drop and drop, regardless of what the weather does. We might see another big Arctic summer storm. We might see the entire surface of the Greenland Ice Sheet melt again, due to a high that's stuck over it. We might see another record low, getting the Arctic another step closer to ice-free conditions.
This isn't ending. It's only just beginning.