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.
The animation on the right consists of NSIDC
sea ice concentration maps, one for each ASI update.
Check out the Arctic Sea Ice Graphs website (ASIG)
for daily updated graphs, maps, live webcam images and
the Arctic Sea Ice Forum (ASIF) for detailed discussions.
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:
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