We tend to focus on the end of the melting season, also known as the minimum, because that's when the ice covers the least amount of water. That's all fine and dandy, but of course, it's just an arbitrary measuring point. For instance, this year's minimum for the JAXA sea ice extent data set was 6th lowest on record, but flash forward to the first week of October and this year's trend line is third lowest on record and could soon be second lowest on record:
This, as always, had to do with the weather, which has been pretty crazy the past two weeks. First, fierce winds pushed back against the ice edge in most of the Arctic Ocean, delaying the ice pack's expansion, while at the same time continuing to melt that last, stubborn sliver of ice extending towards the East Siberian Sea. The result has been a continuing decline of sea ice extent in the Arctic Basin, and to a lesser extent in the East Siberian Sea, where, normally, the trend line should have been going up already (image courtesy of Wipneus, ASIG Regional graphs):
Another factor that has come into play these past few days, is heat. It's mostly coming from the Pacific, where sea surface temperatures are running quite hot again, as can be seen on these DMI sea surface temperature anomaly maps, comparing this year's start of October with those of 2016 and 2017:
The melting season hasn't started in earnest yet, but it seems the Bering Sea hasn't received the memo. For almost the entire winter, sea ice has been reluctant to form there, and now that the Sun has returned, the ice edge has started to retreat to record high latitudes, past the Bering Strait all the way up into the Chukchi Sea. Here's how that looks on Wipneus' regional graph:
To emphasize how truly exceptional this is, here's a comparison with the situation in all other years from the 2006-2018 period (images retrieved from the University Bremen sea ice concentration maps page on the ASIG, click for a larger version):
Now, if this was it, other years would maybe catch up in the next few weeks, but this isn't it. The coupled HYCOM-CICE model from the Naval Research Laboratory forecasts the sea ice to continue to drift northwards, until the end of the month at least:
This is starting to become an annual tradition, here on the Arctic Sea Ice Blog. Just like last year and the year before that, the record for lowest global sea ice minimum has been broken. The lowest global sea ice extent minimum on record (NSIDC and JAXA) was reached two weeks ago. I wanted to wait a bit and see whether the record for NSIDC global sea ice area would be broken too, but it wasn't, although the minimum came in at a solid second place, practically on a par with last year.
And here you see the anomaly of all those trend lines in chronological order, having hovered between 2 and 4 σ (standard deviations) since the 2016 crash:
Not enough Antarctic sea ice melted to clinch the lowest Antarctic sea ice minimum record (coming in second lowest 'only'), and so the decisive nudge was given by the sea ice in the Arctic, refusing to freeze along some of the edges, most notably in the Bering Sea. Here's how the graph for that region looks as of today, with some of the open water even spilling into the adjacent Chukchi Sea, which is highly unusual for this time of year:
Another month has passed and so here is the updated Arctic sea ice volume graph as calculated by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center:
A month of somewhat slowing extent increases has been reflected in the PIOMAS sea ice volume model output. Total volume growth during November 2017 was third lowest for the past decade. 2017 dips below 2011, thus regaining third position again. The difference with number two, 2012, is reduced from 1210 to 733 km3, whereas the gap with crazy winter year 2016 grew some more, from 1142 to 1482 km3.
Here's how the differences with previous years have evolved from last month:
Wipneus' version of the PIOMAS graph shows more clearly how 2017 has moved into third position:
During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Because of issues with data based on the SSMIS sensor aboard DMSP satellites, I mainly focus on higher-resolution AMSR2 data from the Japan Aerospace Exploration Agency (JAXA), as reported on the Arctic Data archive System website. 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.
After an unprecedented warm winter and an unprecedented early opening of the Beaufort Sea, the 2016 melting season isn't showing any signs of shrugging off the 'unprecedented' label. What has struck me most so far, is that unprecedented things have been happening on both the Pacific and Atlantic side of the Arctic.
I've been closely observing events in the Arctic for almost a decade now, and have been writing about them since 2010, and during that time I have gotten used to this sort of see-saw, where fast melting on one side of the Arctic would be compensated by events unfolding slowly on the other side of the Arctic. But this year is different. This year the ice pack is under attack on both sides of the Arctic.
I have written separate blog posts to describe these events (see here and here), and in weeks to come these ASI updates will provide a comprehensive overview on what is happening to the sea ice in the Arctic, and how this melting season is unfolding.
Sea ice extent (SIE)
Let's jump right into it. Here's the latest JAXA SIE graph:That gap is pretty intense. I wasn't kidding when I said 'unprecedented'. Last year - orange line - was already quite spectacular, but this year is crazy.
As commenter Jim Pettit wrote on the Arctic Sea Ice Forum earlier today:
It's been a week since I announced that the ice in the Beaufort Sea was going to come under early pressure. Here's a quick update on what has happened so far, how the forecast played out, and what the short-term conditions for this part of the Arctic will be.
As expected, the Beaufort Gyre kicked into action, big time, with winds causing large cracks in the ice pack, moving it westwards and away from the Alaskan and Canadian coasts. The massive polynyas that are left behind, get partially covered with a thin veneer of ice.
Here's an animation showing the difference between LANCE-MODIS satellite images on the first of the month and two weeks later:
Quite impressive, isn't it? As if someone threw a giant brick into it.
Here's an animation showing all days between April 1st and 14th (the file is somewhat large, apologies if it loads slowly):
As I write this, a storm is battering the ice pack on the Pacific side of the Arctic. It's not as huge as the Great Arctic Cyclone of 2012, but it's pretty decent as far as cyclones go, and it's doing its thing in that part of the Arctic where the ice pack looks weakest, but was strongest at the start of the melting season.The timing of this event is perfect for discussing one of the most important aspects of this melting season.
The image on the top right shows the ice age distribution at the start of the melting season, red being the oldest multi-year ice at that time. Due to a very intense high pressure area over the Beaufort Sea at the end of the freezing season, heavy winds drove the ice pack apart there (a so-called cracking event), causing this multi-year ice to become interspersed with very thin ice. That's the dark blue spots between all the red.
During the very first phase of the melting season the Beaufort Sea region witnessed a heat wave causing a lot of this thin ice to melt out. Because the ice pack wasn't pushed back together again, many of the multi-year ice floes were surrounded by warming waters, and ever larger holes within the ice pack on the Pacific side of the Arctic started to form. The animation below shows what happened between week 27 and week 32, or June 29th to August 9th:
Just towards the end of the animation the holes are showing up. Unfortunately these maps aren't updated until the minimum has hit, but we can still get an idea of what happened after August 9th by checking out the sea ice concentration maps provided by the University of Bremen. The following animation shows how the holes separate a so-called 'arm' of multi-year ice from the rest of the ice pack:
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 2005-2014 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.
I wanted to wait for the latest PIOMAS update and do another melt pond analysis for June, but given the current circumstances and the forecast I've decided to squeeze this ASI update in first.
As we've seen in previous ASI updates this melting season hasn't had a flying start, but it hasn't been as slow as 2013 and 2014 either. With extent going low real fast, but area lagging behind, the compactness numbers indicated little melt pond formation and no divergence to speak of. Melt ponds - and to a lesser extent openings within the ice pack - are important because they lower the ice pack's albedo and soak up a lot of sunlight, preconditioning the ice for further melting. This melting momentum, as I call it, can play a decisive role in the latter half of the melting season, trumping weather conditions.
Of course, weather still plays a very significant role in the final outcome of a melting season. This year hasn't seen any substantial preconditioning and is more similar to rebound years 2013 and 2014 than record years 2012, 2007 and 2011. In fact, this year has been very much like last year, in the sense that there is hardly any movement. Very little ice is transported through Fram Strait to the North Atlantic ice graveyard, and there is no compaction or divergence to speak of because of a lack of strong winds. Most of the extent/area decrease is caused by so-called in situ melting, or melting on the spot.
However, there is one big difference compared to last year and that's heat. Despite a very cold start, there have been several outbreaks of warm air over the ice, slowly but radically shifting the balance between extent and area data. The impact is felt on the surface of the ice pack, but doesn't translate directly into a decrease. Not yet. In theory, it should percolate through after a while, especially if the heat persists. And right now the Arctic sea ice pack is undergoing a massive heat wave which shows no signs of letting up.
More on what has happened and what is going to happen below.
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.
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:
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 2005-2012 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.
Here's another rehearsal for when I grow up and make good videos with a title roll and background music and everything. By the way, I make a big mistake as I go along. Can you hear what it is?
This update should actually be called 'Bye bye, Beaufort and Chukchi', but it doesn't sound as good. As announced in the previous ASI update the trend lines on various graphs have started to drop precipitously, with thin ice on the fringes (Hudson, Baffin, Kara) disappearing fast.
Despite a slow start unlike any other in recent years, which I described in this recent blog post, 2013 is still hanging in there, slowly leaving the less aggressive melting seasons behind and moving towards the record years of 2007, 2011 and 2012.
The question now is how things will proceed, as the amount of easy-to-melt ice is starting to run out. Even though this year's ice pack consists of a record amount of first-year ice, the weather still plays an important role. The interesting thing about last year's melting season was that decrease rates slowed down somewhat when the weather turned bad in July, but didn't stall, like they did in previous years under similar circumstances.
I think the same will go for this year as well, also because area/extent numbers are quite bit higher, and thus still a lot of melting potential. But there's no telling what could happen if the weather is very conducive to melting/compacting/transport for a week or two, and it looks like we're having some of that up ahead.
Sea ice area (SIA)
July is a month where trend lines on the Cryosphere Today
sea ice area graph get divided in the two camps of winners and losers, with 2010 moving from one to the other. Because of steady, substantial drops since the last week of June the 2013 trend line has slowly started to move from one camp to the other.
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