What a coincidence. Just like last month, I will have to precede the PIOMAS update with a short news flash that a very strong cyclone is barreling through the Arctic. But this time too, the cyclone will be short-lived, and so it's not entirely clear whether, on the whole, it will be damaging or beneficial. It has gone further into the Arctic this time.
Either way, the cyclone' has bottomed out at 968 hPa according to Environment Canada, which is just 2 millibar more than last month's cyclone:
With their sub-970 hPa pressures these cyclones come close to the Great Arctic Cyclone of 2012 (963 hPa), but I think they lack in other parameters such as longevity to really deserve the GAC epithet. Nevertheless, to see two of these monsters in June and July in what hasn't otherwise been a very noteworthy melting season so far, is quite noteworthy. We might even see another one before the melting season is over, which could be a sign of some yet to be identified change going on in the Arctic, causing these extremely warm winters, followed by relatively cold and cloudy summers.
But that's all speculation. Let's look at the updated PIOMAS volume numbers.
Before kicking off this latest PIOMAS update, there's a little piece of information I'd like to share: A massive cyclone is passing through the Arctic right now. The cyclone has bottomed out about half a day ago at 966 hPa, which is slightly lower than the 968 hPa storm we saw at the end of August 2016, and slightly higher than the Great Arctic Cyclone of 2012 (963 hPa). Even though pressure levels are similar, this current storm can't match the other big ones when it comes to longevity. But at the same time, bear in mind it's only June, and not August.
And also remember what IARC chief scientist John Walsh said back in 2012:
This past week’s storm was exceptional, and the occurrence of Arctic storms of extreme intensity is a topic deserving closer investigation. With reduced ice cover and warmer sea surfaces, the occurrence of more intense storms is certainly a plausible scenario. The limitation at present is the small sample size of exceptional events, but that may change in the future.
I think it's safe to say it's changing.
Here's an image of the moment this current cyclone reached its lowest pressure, according to Environment Canada:
I will soon discuss the consequences of this storm for the ice pack, and apologize for not having started writing regular ASI updates yet (too busy).
Okay, now for the PIOMAS update.
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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:
According to the PIOMAS model, volume decrease for May 2018 has been below average: 2285 vs 2650 km3. This means that 2018 is 5th lowest right now, and the difference with last year has grown to a massive 1915 km3, which is 299 km3 more than last month. It has also been overtaken by 2012, which saw a huge volume reduction in May. Likewise for 2016 and 2011, with 2010 not far behind now either.
Here's how the differences with previous years have evolved from last month:
There's just no end to this run we have had with anomalously warm temperatures, and storms blowing in from the Atlantic.
As we speak, a very powerful winter storm is battering the ice pack on the Atlantic side of the Arctic, as shown on this SLP map (source):
Lowest pressure was probably reached yesterday at 957 hPa, but it's still raging at 958 hPa right now. Remember, the GAC-2012 clocked in at 962 hPa, and the series of powerful storms we saw last August bottomed out at 968 hPa. Storms tend to be stronger during winter.
In the short term this might actually increase sea ice extent, as strong winds will be pushing out the ice towards the Atlantic, but in the longer term it will probably be detrimental to the ice pack, as a lot of the ice being pushed out is older and thicker. The storm and the moisture it brings with it, will also cause more snowfall, insulating parts of the ice pack so that the ice grows thicker at a slower pace, and thus be thinner than it could have been when the melting season starts.
The ECMWF forecast is showing another strong storm forming 9-10 days from now, but that's very far out, and so the forecast can change. But the storm we're seeing right now (I briefly mentioned it in this previous blog post), was also forecast 10 days ago and then came about. We'll have to wait and see what happens.
Now, what is causing all these storms and all that moisture to be transported all the way to the Arctic? We saw the same thing during last year's winter, but this time it's even worse. It might have to do with all the heat that the recent El Niño brought with it, but previous El Niños didn't seem to have such a marked effect. Perhaps it's something else, another reaction to Arctic sea ice loss, some sort of vicious cycle.
Yesterday this video was posted on Peter Sinclair's ClimateCrocks blog, showing an interview with Dr Jennifer Francis (Rutgers University) at the AGU 2016 Fall Meeting this past December:
Another effect of this possible feedback is more clouds during summer, shielding the ice from the Sun's rays. But as we saw during last year's melting season, this didn't help much (except for preventing new sea ice extent/area records). That's probably because heat doesn't just enter the Arctic via the atmosphere, but via ocean currents as well.
As reported in the last ASI update, the forecast Dipole has now set up. Yesterday's last analysis chart provided by Environment Canada, at 18Z, showed the high pressure moving in via the Bering Strait at 1037 hPa, while a rapidly weakening storm that had moved in from Siberia (lowest central pressure was 967 hPa, two days ago) was still at 974 hPa on the other side of the Arctic. This then evolved to a massive 1041 hPa on one side of the Dipole, and 977 hPa on the other:
That's a humongous pressure gradient of 63-64 hPa! You don't see that often around this time in the Arctic, a not so nice story for the grandkids. Right now, the high is still at 1041 hPa, but the low has weakened further to 980 hPa. That's still a pressure gradient of 61 hPa.
It means very strong winds are blowing over the ice pack, from Siberia to Canada, compacting the ice pack and further pushing open water towards the pole, as can be seen on this animation of Uni Bremen sea ice concentration maps:
If one looks carefully at the ice in the so-called Wrangel Arm, you can clearly see the ice flash in and out of existence. There comes a point where the ice no longer flashes back, but in the meantime it makes for wild swings on the CT sea ice area graph, as calculated by Wipneus:
A high-pressure area has been moving in over the Beaufort Sea lately. It's quite big and quite high in pressure. Environment Canada has the current pressure there at 1042 hPa:
I've coloured the land masses to make it easier to orient. I've also put in the red arrows to show which way the winds blow along the so-called isobars.
This is the second notable high of this year, following another big one in February that produced strong winds that pushed the ice away from the coast. This phenomenon called the Beaufort Gyre resulted in what we call a cracking event around here (see this blog post). Of course, the Arctic was plenty cold around that time and so the leads froze over again, but the marks are still visible on this AVHHR image (provided again by Environment Canada):
On the one hand those leads let heat escape from the ocean water, on the other hand the thin ice between the enormous floes will melt out easily as soon as sunlight and higher temperatures start taking over, possibly making the entire zone more vulnerable early in the melting season.
The reason I've decided to dedicate a blog post to this, has to do with the current ECMWF forecast for the coming 6 days:
I think this winter is going to get studied like crazy, for quite a while. It’s a very interesting time. Jennifer Francis, Washington Post
The extraordinary temperature anomalies in the Arctic since the start of the year haven't gone unnoticed in quite a few media outlets, and I apologize for not having joined the fray of actuality. On the other hand, context trumps actuality, as we need to compare to previous years and get a feel for what this prelude to the melting season may mean. In that sense, I'm early with this year's winter analysis (compared to last year).
Let's start studying like crazy, shall we?
It's a lot of text and images, so if you're feeling a bit tl;dr-ish today, skip to the conclusion at the bottom of the page.
Surface air temperature
Here are the monthly temperature graphs for November-February in the Arctic Circle, from 2005/2006 to the past winter, based on the NCEP reanalysis dataset:
Last November saw the highest average monthly temperature in the 2005-2015 record, followed by a lower December, relatively speaking. Things then get a little bit crazy after the turn of the year, with the January 2014 record getting broken by almost 3 °C! February isn't far behind either, almost 1.5 °C higher than the already 'warm' February of 2014. This is unprecedented.
To see where temps were least low, I've created average temperature maps using the Daily mean composites page from NOAA's Earth Science Research Laboratory website, comparing the 2015/2016 freezing season to those preceding the years with the lowest minimums on record (click for a larger version):
Winter is supposed to be a time when things quiet down in the Arctic, animals hibernate in complete darkness, and all that can be seen from satellites is this great, icy mass getting bigger and bigger. That's how it goes most of the time, despite the spectacular summer sea ice losses of the past decades. But of course, there are exceptions, and this winter is one of those. In fact, it's an exceptional exception.
I want to highlight a couple of things to give you an idea of what's going on in the Arctic right now. As some of you may already know, this year's trend line is the lowest on record in practically every graph (see here). So far, it has played a major role in the breaking of Global sea ice area and extent minimum records, and it looks highly possible that last year's Arctic sea ice maximum record gets broken too. Mind you, that record was already spectacularly early and low, which is why I referred to it as Mad Max at the time.
It's a bit too early to be calling the max, which I vowed never to do again anyway, but here's the current situation on the Cryosphere Today sea ice area and JAXA sea ice extent graph (as provided by ADS-NIPR):
2015 peaked on this date in the CT SIA data set, but this year is currently 700K lower (last week's preliminary peak was almost 600K lower). The 2015 maximum occurred on February 15th in the JAXA SIE data set, but this year's preliminary peak is almost 274K lower. That's no small change, if things stay this way.
When area/extent is exceptionally low, it's usually a sign of something going on one side of the Arctic, while things are relatively quiet on the other side. This year, however, there's stuff going on on both sides of the Arctic. I'll start with the Pacific side of the Arctic, where regional extent is again very low in the Bering Sea, though high in the Sea of Okhotsk (these graphs are produced by Wipneus and can be found on the Regional Graphs page):
Everybody wants clean air. We in the West do, the Chinese do, and it'll also be high on the wish list of Indians and people from other developing nations, once their living standards go up. But good things can also have drawbacks. And in this case it could be a drawback that a place like the Arctic really doesn't need, as this recent Alaska Dispatch News article explains:
Cleaner atmosphere means more Arctic sea-ice melt, study says
This April 9, 2015 natural-color satellite image shows sea ice and cloud streets between Labrador and Greenland. A recent study found that cleaner air -- the result of efforts to reduce emissions of sulfur dioxide and other harmful aerosols -- will also have the unwelcome side effect of hastening the melt of Arctic sea ice.NASA Earth Observatory
To protect human health and safeguard the environment, governments and utility companies around the world have worked -- successfully -- to reduced the amount of sulfur dioxide released into the atmosphere.
But there's a downside to cleaning the air of sulfur dioxide and similar pollutants: Arctic sea ice is more exposed to solar heat, and more of it melts.
Now, Environment Canada researchers, in a study published in Geophysical Research Letters, have put a number on the sea-ice melt that reduced emissions of sulfur dioxide (and certain other aerosols, tiny particles that are suspended in the atmosphere) are expected to cause: about 400,000 square miles or 1 million square kilometers.
That's the amount of ice melt, according to the study's calculation, that's likely to be attributable to reductions of human-caused emissions of sulfur dioxide and similar light-reflecting air pollutants by the end of the century. That figure will account for 25 to 40 percent of the expected seasonal sea-ice melt, depending on future emissions of carbon dioxide and other greenhouse gases, the study says.
That doesn't mean there should be a slowdown in air-quality controls, said one of the study’s authors.
“We want to avoid that interpretation,” said Nathan Gillett, an Environment Canada research scientist and manager of the Canadian Centre for Climate Modelling and Analysis.
Removing sulfur dioxide and other pollutants from the air is important to protect people and the environment, even if it also removes some material that shields Arctic sea ice from melt, Gillett said.
“We’re really just pointing out that it’s part of the picture and should be considered,” he said. “We’re not trying to weigh costs and benefits of sulfur dioxide here."
This is a continuation of Part 1, wherein I posted several graphs and maps depicting the 2015 minimum, and the weather conditions leading up to it (Tamino has a great blog post showing the long-term sea ice extent trends, all of them, not just the cherry-picked, meaningless one the GWPF selected to mislead).
Before jumping into the ice age and volume data that is (perhaps) most interesting, intriguing, but also incomplete, I want to refer to one more factor that - besides weather conditions and ocean heat flux - can play an important role in how a single melting season plays out: land snow cover.
Here are the monthly Northern Hemisphere snow cover anomaly graphs from the Rutger University Global Snow Lab during the melting season:
It's clear snow cover got pretty low during June and July. It's a bit of a chicken-or-the-egg kind of mutual influence thing, with an albedo feedback leading to warming over land, leading to increased snow melt, etc. which then starts to influence the Arctic and its sea ice as well. There's been ongoing speculation on this correlation between land snow cover and sea ice for years now, and my guess is that there's a there there, but as it isn't the only influence, it's hard to quantify it. Either way, it has to do with (global) warming, as attested by commenter Al Rodger's guest blog a few years ago: The untold drama of Northern snow cover.
And so we turn to multi-year ice. I'll repost this animation from a blog post I posted two weeks ago, showing how virtually all of the older, thicker multi-year ice on the Pacific side of the Arctic has melted out this melting season:
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:
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