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.
July 27th 2014
The 2014 melting season so far:
- coming out of an over-all mild winter
- prolonged cold, cloudy start, very little melt ponds
- at the end of the start some weather patterns conducive to melting
- after a couple of weeks high pressure areas are replaced with lows
And that's the point where we are at right now. As forecasted two weeks ago, the low times have led to slow times. Not that there has been any prolonged period of fast declines this year. Sure, high pressure was dominating the Arctic for a while, leading to clearer skies and thus more insolation. But more is needed for sea ice area and extent numbers to drop substantially. Things like wind to bring in warm air and move the ice around.
Like a band once sang: "You're perfect, yes, it's true, but without me you're only you." The same applies to high pressure areas. Yes, they are conducive to melting, but without lows, there are no strong winds to speak of, there's no transport, things get static. There has been relatively very little movement this year. At least when lows dominate (like last year), the ice pack gets dispersed, with holes showing up all over the place.
The big question now is whether 2014 ends up near 2013 (higher even), or not.
Sea ice area (SIA)
Occasional century breaks are offset by low daily losses, keeping the 2014 trend line on the Cryosphere Today graph near the top of the 2005-2014 range:
Last year the trend line completely stalled around this time of year. It will be interesting to see if there's a repeat.
Here's the link to my CT SIA spreadsheet.
Sea ice extent (SIE)
On the IJIS graph the 2014 trend line has now definitely moved away from the top years, going well above 2013, making the graph more in line with the CT SIA graph:
The current daily average for July is among the lowest in the 2005-2014 period, 20K per day lower than 2012 and 2013.
Here's the link to my IJIS SIE spreadsheet.
Cryosphere Today area per IJIS extent (CAPIE)
With SIE stalling, and SIA keeping more or less the same rhythm, CAPIE has finally started to drop compared to two weeks ago when the daily value was higher than any other year in the 2005-2014 period. But it's still among the highest, which means that basically there's little divergence and a low melt pond cover fraction. I don't expect it to go much lower, as in a couple of weeks what little melt ponds there are, start freezing up again.
Regional SIE and SIA
Regional graph of the week, taken from the Regional Graphs page on the ASIG:
For this update we turn to the Beaufort Sea. As can be seen on the graph above the melt there is comparable to previous years, except for 2013. Although the SIA trend line was dropping hard (see graph here) while the Sun was shining a lot over this region during parts of June and July, this speed has now leveled off.
Wipneus posted this animation a couple of days ago on the ASIF, based on his own calculation of AMSR2 data, stating: "As a cyclone moved over the Beaufort, the ice there is visibly left in a worse state."
Wipneus sent me this custom-made map that shows what has been happening in the past two weeks. Red = ice two weeks ago, open water now; blue the other way around:
The Beaufort Sea is important, because a lot of multi-year ice moved into it during winter:
The amount that survives in the coming weeks, will play a role in the general health of the ice pack. This is something to keep an eye on.
Sea Level Pressure (SLP)
Here's the two-week animation of Danish Meteorological Institute SLP images:
The 6-day forecast from the last ASI update came about, with a low moving in on the American side of the Arctic (see regional graph of the week above to see the effect on the ice in the Beaufort Sea). The low then moved out again via the central Arctic.
Like I wrote at the time: "except for relative thinness (we assume) in some fringe areas, sea ice decrease could stall completely as soon as the weather becomes less conducive for melting and stays that way for a while." This is obviously what happened, and it is also tied to that slow start of the melting season, a period when melt pond formation is probably crucial for the remainder of the melting season. To put it simply, a lack of melt ponds doesn't help 2014 pull through slower periods, like we saw happen so explicitly in 2012.
Towards the end of the animation we see high pressure regaining control of the American side of the Arctic, and so it's with particular interest that we look at what the ECMWF model is forecasting for the coming 6 days (click for a larger version):
It looks like the high is remaining put over the Beaufort again, strengthening even beyond the 6-day forecast (which isn't very reliable, so we'll have to wait and see how this plays out), and also spreading over the Chukchi and East Siberian Sea. This could be bad news for the ice there. If this set-up persists for a while, sea ice extent and area decrease should accelerate again.
It's been relatively warm over the Canadian Archipelago recently, and still is, which could have consequences for the Northwest Passage. The ice is still looking relatively strong over there, and just like last year the central passage might remain closed, but it could open up if these temps keep up:
Given the ECMWF SLP forecast, it's interesting to see what the GFS temperature anomaly forecast displayed on the ClimateReanalyzer website (from the Climate Change Institute at the University of Maine) is showing:
It looks like therewill be an end to the warm spell over the Canadian Archipelago in the coming days and the Kara region remains cool, but at the same a lot of heat is pulled over Eastern Siberia, which will actually spill past the coast line, far into the ice pack. This is not forecasted to last long, but won't be good for the ice nevertheless.
As for sea surface temperatures, things have been cooling down practically everywhere, compared to two weeks ago, and now definitely look cooler than August 4th 2013, never mind 2012 around this time.
This is one of the factors behind the slow times.
The Arctic is slowly creeping towards the final stage of the melting season, with 2014 now even trailing last year after two weeks of cold and cloudy weather over large parts of the Arctic. But 2013 stalled big time around this time last year, so if the current forecast plays out, the difference shouldn't become larger. 2014 might even dip below 2013 again.
This forecast needs to be extended though, at least for a while, if 2014 is to end below 2013. Of course, there still is quite a bit of melting potential in regions like the Kara, Beaufort and East Siberian Sea, but there is not much help to be expected from melt ponds, sea surface temperatures or the ice pack's compactness.
It all comes down to insolation and wind now.