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.
May 19th 2014
Welcome to the first update of the 2014 melting season.
There are two things that determine the outcome of a melting season: initial ice state and subsequent weather conditions. The last two melting seasons were so diametrically opposed that we actually learned a lot in this respect. Or, at least I did.
In 2012 the initial ice condition and first half of the melting season was so conducive to massive sea ice melt, that it didn't matter all that much what the weather did during the second half of the season. Even during cloudy, colder periods sea ice extent and area kept dropping. In 2013 it was the opposite: initial ice state (probably influenced by the cracking event of March that year) and a cold, cloudy first half of the melting season were slowing the sea ice melt so much that even spells of clear, warm weather couldn't change the melting season's outcome.
Of course, we don't know what the weather will be like weeks and months from now, but we can somewhat estimate the initial ice state (see my 2013/2014 Winter Analysis) and check the sea ice pack's pulse in these crucial first weeks of the melting season. One very important influence I've been obsessing over every now and then, is the amount of melt ponds on the sea ice. These small lakes on ice floes can greatly accelerate melting as they decrease albedo, meaning that more sunlight gets absorbed by the ice.
I've always known this was important, but have now become convinced that it could be of paramount importance, in the sense that it can perhaps not make, but definitely break a potential record melting season. And all of it happens in May. Melt pond May. And probably the first half of June too.
I'll be focusing on this a lot in weeks to come.
Sea ice area (SIA)
This is the time of year when the trend lines on various sea ice area and extent charts start to converge with differences becoming more prominent again in June. It can still convey some information, as we saw last year on the Cryosphere Today SIA graph. The 2013 trend line started the month out low, but was highest at the end of it. This was a sign (in hindsight, I didn't see it as such at the time) that cold and cloudy conditions were already having a big influence on the final outcome of the melting season. The slow SIA decline meant that there were less melt ponds than in years before.
Mind you, I'm not saying that SIA or SIE numbers in May are a proxy for melt pond cover fraction, but last year really jumps out in this respect. This year the trend line is more or less in the middle of the pack, as you can see on this graph based on the latest data:
Sea ice extent (SIE)
Things look different on the IJIS sea ice extent graph, with 2014 going second lowest after 2006 (and 2004 according to Espen on the Arctic Sea Ice Forum). Here's the graph based on the data:
Here's the link to my IJIS SIE spreadsheet.
Regional SIE and SIA
Regional graph of the week, taken from the Regional Graphs page:
Sea ice has disappeared quickly from the Bering Sea (and the Okhotsk Sea) this year, with sea ice in the Chukchi Sea also declining faster than usual.
The map below, custom-made by Wipneus for this update, shows the changes over the past two weeks. The map is made using University of Hamburg AMSR2 data. Red = ice two weeks ago, open water now; blue the other way around:
You can quickly compare this year's sea ice cover and concentration with previous years, using the Concentration maps page on the Arctic Sea Ice Graphs website.
Sea Level Pressure (SLP)
Of course, sea level pressure plays a crucial role in determining the position and percentage of melt ponds on the Arctic sea ice pack, as it gives an idea of where the open skies are and if there is a transport of warmer air from lower latitudes into the Arctic. Open skies mean lots of insolation and are there where the SLP is high.
This two-week animation of Danish Meteorological Institute SLP images shows what has been going on with regards to SLP:
A short-lived cyclone was pushed away by a high pressure system coming in from the American side of the Arctic, causing a short-lived Dipole set-up, ending with another cyclone going towards the centre of the Arctic Ocean. In short, nothing conclusive. May 2014 isn't jumping out so far, compared to previous years on the SLP Patterns page on the Arctic Sea Ice Graphs website.
Let's see what the weather will be like for the coming 6 days according to the ECMWF model (click for a larger version):
That cyclone towards the end of the DMI 2-week animation, moves over to the centre of the Arctic and stays there for a couple of days, pulling in air from Siberia that is above freezing over the Siberian Seas, and pulling the sea ice away from the Siberian coast (which has already started and is showing up on the sea ice concentration maps). After that high pressure more or less takes over again.
The forecast, of course, becomes less trustworthy as it goes further out, and in the past couple of days there have been quite some oscillations from one ECMWF forecast to the next. So we'll have to wait and see.
Temps have been low lately over much of the Arctic, which of course reduces the amount of melt ponds. This NOAA/ESRL 1-day anomaly map shows the current situation (the 7-day and 30-day maps can be found on the ASIG):
The trend line on the DMI 80N temp graph started dipping at almost exactly the same time as last year, now going up a bit again:
As far as sea surface temperatures are concerned, things have been warming up in the Atlantic sector over the past weeks and are perhaps slightly warmer than a week later last year, but the colours on these maps can fluctuate:
The start of this melting season has been a mixed bag so far, with some similarities with regards to last year, like cyclones dominating and relatively low temps, but perhaps not that strong either. It was around this time, in the last 10 days of May that 2013 really began to deviate with a very persistent cyclone dominating the Arctic for weeks. There is no sign of that on the weather forecast maps so far.
On the other hand, SIE and SIA are relatively low for the time of year, and those cold temps seem to be confined to the Arctic Basin so far, with lots of interesting things already happening on the fringes, like the relatively early opening up of the Eastern Siberian Sea.
It will take a couple more weeks for more info to roll in. We will then have a somewhat vague idea of those initial ice state conditions and what happened during this crucial first half of the first half of the melting season. If we can guess what is happening with regards to melt pond formation, we might at least be able to tell if a new record is a possibility.
I'm not ruling it out, of course (one mustn't rule things out when it comes to the Arctic), sea ice volume is as low as the last couple of years, but there is more multi-year ice this year and the heart of the Arctic seems to have gained some strength due to last year's rebound (see, again, the 2013/2014 Winter Analysis). It now all depends on the weather.
Which we'll be watching here and on the ASIF. Enjoy the Arctic sea ice, it's the only Arctic sea ice you've got.