During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2013 period (NSIDC has a good explanation of sea ice extent and area in their FAQ). I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything of particular interest.
August 24th 2014
Purely from a melting perspective - never mind the consequences which are already happening, or the way the public views AGW - this has been quite a boring melting season. It has some interesting features nevertheless, like the Northern Sea Route opening yet again and clear sailing up to 85N (more on that later this week). And we still don't have an answer to the question which of the two rebound years, 2013 and 2014, will end up with the lowest minimum. Which in itself is still kind of exciting.
The late momentum that started 2-3 weeks ago has kept ice decline steady, but it wasn't enough to cause massive drops. There was some compaction and quite a bit of melting on the Pacific side of the Arctic, but this was offset somewhat by refreezing melt ponds and a lack of transport on the Atlantic side of the Arctic. The momentum has now stopped building up, as insolation has practically stopped playing a role and the minimum will largely be determined by compaction and transport.
We'll have to see what the year of in situ melting can come up with as we enter the last few weeks of the melting season.
Sea ice area (SIA)
With that massive melt pond refreeze on the Pacific side of the Arctic, the 2014 trend line (on the Cryosphere Today graph) was highest in the 2005-2014 period for a couple of days, but has now started dropping again. According to Wipneus, who estimates the CT SIA numbers two days ahead on the ASIF, it will continue to do so, and thus will get closer to the 2013 trend line:
Here's the link to my CT SIA spreadsheet.
Sea ice extent (SIE)
On the IJIS graph the 2014 trend line has continued to drop very steadily, and is now slowly dipping under the 2013 trend line, which had started to stall around this time last year:
Here's the link to my IJIS SIE spreadsheet.
Cryosphere Today area per IJIS extent (CAPIE)
I think it's safe to say that CAPIE reached its minimum percentage a while back, on July 25th to be precise, which is very early (just like last year). It wasn't just very early, but very high as well: 70.4%. For comparison, 2012 noted a minimum of 59.7% on August 12th.
But it didn't stop there. After the minimum, the CAPIE percentage for this year shot up like crazy, making for an amazing sight on the CAPIE graph (see below). This year has really been marked as the year of in situ melting, with little momentum (melt ponds and open water between floes) and transport. That makes this possible:
Read the CAPIE segment in ASI 2014 update 2 for a more thorough explanation of what CAPIE stands for.
Here's the link to my updated CAPIE spreadsheet.
Regional SIE and SIA
Regional graph of the week, taken from the Regional Graphs page on the ASIG:
This week we turn to the Chukchi Sea, where the ice took quite a battering during the last two weeks, with lots of Sun and warm compacting winds from the North Pacific. It resulted in this custom-made Wipneus™ map using ASMR-2 data from Uni Hamburg, that shows the changes in the Chukchi in the past two weeks. Red = ice two weeks ago, open water now; blue the other way around:
There was a hole, but it got assimilated by the open water.
As said, the Northern Sea Route has opened yet again (what, 8th year in a row now?) and it's possible to sail up to 85N thanks to the Laptev Bite, much earlier than last year. More on that this week.
Sea Level Pressure (SLP)
Here's the two-week animation of Danish Meteorological Institute SLP images:
We see how the high-pressure area that dominated for a couple of weeks dissipates and moves away from the Beaufort, with lows now pushing in from Siberia. This in turn has caused something of a pressure gradient right across the Arctic, causing some transport on the Atlantic side of the Arctic. Not that much through Fram Strait, but rather through Victoria Channel (formerly and erroneously known as Olga Strait) between Svalbard and Franz Josef Land, leaving patches of low concentration in its wake.
It will be interesting to see how large these can get before freezing over again. Last year saw rather large patches of open water near the Pole. But then again, 2013 was the year of persistent cyclones pushing the ice pack apart. This year it's more compact.
The 6-day ECMWF weather forecast shows more of the same, with cyclones taking over the Arctic (click for a larger version):
This is a bit of a double-edged sword. Normally, low pressure areas mean clouds, lower temps, ice pack dispersion. But as we now enter the transition phase between melting and freezing season, open skies can cause more heat to leave than enter the Arctic. In this sense, clouds can dampen the fall in temperatures.
It's very complex, and so there's no telling (at least, for me) what will happen exactly in the coming week. It does seem as though there will be a stop to what little transport there has been on the Atlantic side of the Arctic.
The relative heat over the North Pacific is still visible on the NOAA/ESRL/PSD/NCEP surface air temperature map:
But north of 80° latitude, just like every year, temps have started to go down, as can be seen on the DMI 80N temp graph:
Speaking of which, SSTs in the North Atlantic still don't look too high on the DMI SST anomaly map, although elsewhere there's still a lot of red to be seen (here are the maps for August 25th 2012 and August 18th 2013):
With just 2-4 weeks left in this melting season, we wait and see where the minimum will end up. With 2014 relatively high, but steadily declining, and 2013 stalling around this time, the race is still somewhat exciting. Unless 2014 completely stalls over the next two weeks, which of course, is also possible.
But more important than this rearguard action, are the implications for ice pack health. As we have seen, modeled volume is now higher than it has been for a couple of years, and with a substantial part of the ice on the Pacific side of the Arctic surviving, multi-year ice will see another rebound. Last year's volume rebound had been all but wiped out at the start of this melting season, but maybe the ice pack gets some more flesh on the bones after this year of in situ melting.