During the melting season I'm regularly writing updates on the current sea ice extent (SIE) as reported by IJIS (a joint effort of the International Arctic Research Center and the Japan Aerospace Exploration Agency) and compare it to the sea ice extents in the period 2005-2010. NSIDC has a good explanation of what sea ice extent is in their FAQ. I also look at other things like sea ice area, concentration, volume, temperature and weather forecasts, anything that can be of particular interest. Check out the Arctic sea ice graphs webpage for daily updated graphs, maps and live webcam images.
August 20th 2011
Switching weather patterns slowed down the sea ice decrease, as they often do. I must admit I was expecting a bit more after the massive drop in sea ice extent of 127K (the second highest daily drop IJIS recorded during August) last week. I was also expecting CAPIE to go up again (after it hit a record low percentage on August 12th), but because extent would catch up, not because area would shoot up by more than 100K in two days.
On the other hand, despite adverse weather patterns, this year has managed to nibble away at 2007's lead and halved it in 10 days time. This of course says something about the state of the ice, which is so weak it melts anyhow or easily gets compacted in specific areas (see the latest animation). Perhaps not this year, but we are approaching a time when weather patterns will no longer be able to prevent extent and area numbers to drop through the floor.
To repeat what I wrote on August 9th: "If 2011 manages to get within 150K of 2007 by August 20th, the race is on again." I don't think this will become about, as the difference is 250K with only one day to go. It's now very probable that the 2007 minimum extent will remain the record. At the same time the combination of slush puppie ice and relatively high sea surface temperatures make it difficult to rule anything out, as we enter the final weeks of the melting season.
Nothing in the Arctic is a dead certainty.
Sea ice extent (SIE)
Here's the current IJIS SIE graph:
As said, 2007's lead has been almost halved from 470K to 251K from August 9th to 19th. Except for 2008 which had a very big extent decrease in August, 2011 has managed to increase its lead over other years. Barring a really early end to the melting season, this year is bound to end up somewhere in the top 3.
The current difference between 2011 and the other years is as follows:
- 2005: -608K (-45,000)
- 2006: -813K (-37,697)
- 2007: +251K (-57,041)
- 2008: -391K (-70,333)
- 2009: -598K (-48,654)
- 2010: -383K (-51,736)
Between brackets is the average daily extent decrease for the month of August. 2011's average daily extent decrease for August is currently -62,508 square kilometers.
If 2011 loses as much sea ice extent as...
- 2005 did after this date it will bottom out at 4.71 million square km
- 2006 did after this date it will bottom out at 4.96 million square km
- 2007 did after this date it will bottom out at 4.51 million square km
- 2008 did after this date it will bottom out at 4.32 million square km
- 2009 did after this date it will bottom out at 4.65 million square km
- 2010 did after this date it will bottom out at 4.43 million square km
Sea ice area (SIA)
After a massive drop of more than 200K square km Cryosphere Today sea ice area basically hasn't moved for 6 days now, with increases and decreases alternating. Consequently, 2011 has relinquished its number 1 position and is now 174K square km behind 2007. On this graph made and updated by Larry Hamilton we can see how close this year is to equalling 2007, 2008 and 2010:
What with the increases in the past days, the Cryosphere Today SIA anomaly graph has gone up a bit again:
When it comes to the Regional Graphs it looks like the Arctic Basin and Canadian Archipelago have reached last year's minimum with a few weeks left to go. Because of massive divergence of slushy ice in the East Siberian Sea SIA is still higher there than last year, which makes it a key area for potential new records. The same goes to a lesser extent for the Greenland Sea, which is also has a relatively high SIE and SIA because of very slow ice transport through Fram Strait.
Cryosphere Today area per IJIS extent (CAPIE)
This year's trend line has gone up a bit again due to the SIA increases, but is still relatively low for this time of the year, meaning there is a lot of compaction potential, should weather patterns choose to push the ice pack together:
Unfortunately last week's distribution of sea level pressure areas didn't remain stable for a few days longer, as it would have been interesting to see what it would have done to area and extent numbers. Right now, highs and lows are in exactly the wrong opposing spots for sea ice decrease. Of course, cloudy conditions now retain heat as the sun is setting earlier every day and air temperatures start dropping below freezing. But in this final phase of the melting season it's ice displacement and compaction that determine the numbers. As much as the ice allows it of course.
Here's an animation of SLP images from the DMI Centre for Ocean and Ice of the past week:
We see how that huge high quickly dissipated and disappeared altogether, with a new high appearing north of Scandinavia. There hasn't been measured any particularly low sea level pressure in the Arctic this past week, so no really big cyclones to shred the ice pack to pieces.
The Arctic Oscillation Index has been quite negative and is now moving back up again. The forecast ensemble is showing neutral conditions for the coming two weeks. According to the ECMWF weather forecast maps the highs and lows remain as they are, which means we won't be seeing any increased SIE and SIA decreases the coming week:
The highs are going to take over the entire Atlantic side of the Arctic and extend over Greenland. This will prevent any meaningful ice transport through Fram Strait. No big cyclones are to be expected yet either, so the slush puppie ice is spared for now.
Mind you, the ECMWF forecast maps change quite radically from one update to the next, meaning it's not entirely clear what is going to happen exactly. We'll have to watch it on a day-to-day basis.
Anything is always possible, but it will be difficult for this year's melting season to go below the 2007 record minimum extent. Another 10 days or so and we'll have to start pricking up our ears to see if we hear a certain lady with a certain BMI index is clearing her throat. If the diva takes her time, 2011 will certainly go below 2010 and thus secure a top 3 spot.
There's a lot of melting and compaction potential, but the key question as always is whether time and weather conditions will permit full use of it. That's a lousy conclusion, but all I can do for now. :-)
TIPS - Other blog posts and news articles concerning the Arctic and its ice:
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