Arctic Sea Ice

Circumnavigating Greenland

A quite spectacular event took place during the past two weeks, and if it had continued for a while longer, I'm sure it would've been reported widely. It's something I've semi-jokingly alluded to when setting up this blog back in 2010, in my third blog post called Dire Straits, and a partial answer to the question commenter fredt34* asked at the time:

The big hole opening in East Greenland re-activated my interest for this question: will we see Greenland being circumnavigable this year? If not, when?

That was July 23rd 2010, and now a little over 8 years later, we have almost seen it happen: a corridor of open water between Fram Strait and the Lincoln Sea (where Nares Strait starts). Here's an animation of NASA EOSDIS Worldview satellite images showing what has happened during the past two weeks, ending yesterday (click for a slightly larger version):

And here's the animation with only the first and last images, two weeks apart:

PIOMAS August 2018

PIOMAS data came in a bit later this month, and I'm a bit later still, but this gives us an opportunity to look at what may happen during the second half of the month.

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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:

Given the heat on the Siberian side of the Arctic and extensive melting in the Kara and Laptev Seas I had expected a larger drop. Nevertheless, a loss of 6229 km3 of sea ice volume is well above the 2007-2017 average of 6020 km3. This essentially means that 2018 has caught up some more with the years in front of it, and even slipped below 2016 (the difference is a mere 17 km3), which means it's in 5th position as of July 31. The difference with 2012 has been reduced with 610 km3, and is now 907 km3.

Here's how the differences with previous years have evolved from last month:

Aerosols and Arctic sea ice loss

A great article was posted on the Guardian website yesterday, written by Dr John Abraham, in which he highlights research that shows that if it weren't for aerosols, Arctic sea ice loss would've been even greater:

Pollution is slowing the melting
of Arctic sea ice, for now

Human carbon pollution is melting the Arctic,
but aerosol pollution is slowing it down

NASA satellite photo of the minimum extent of Arctic sea ice in 2005 that occurred on September 21, when the sea ice extent dropped to 2,05 million square miles (53 094 969 million square kilometers). Photograph: HO/AFP/Getty Images

The Arctic is one of the “canaries in the coal mine” for climate change. Long ago, scientists predicted it would warm quicker than other parts of the planet, and they were right. Currently, the Arctic is among the fastest-warming places on the planet. Part of the reason is that as the Arctic warms, ice melts and ocean water is uncovered. The ocean is darker than ice so it in turn absorbs more sunlight and increases its warming. This is a feedback loop.

Another reason is that the Arctic doesn’t get that much sunlight so increased energy from the atmosphere has a bigger influence there than it would have elsewhere.

Scientists have looked to the Arctic for clues and hints of human climate change over the past decades. The fact that the Arctic is warming has led to a 70% reduction in the volume of summer sea ice – an enormous loss of ice.

Decline in September Arctic ice extent (not volume). Illustration: NASA

A recent paper just published in the Journal of Climate by the American Meteorological Society takes an in-depth look at how fast the Arctic ice is melting and why. According to the paper, the authors completed a detection and attribution study of Arctic sea ice decline from 1953 to 2012. That is 60 years of data that tell the picture of climate change. The “detection” part of this study was about detecting what long-term trends are apparent over these six decades. The “attribution” part of the study is figuring out what is the cause of the trends.

Why six decades? Well the authors wanted to go back as far as they could while still accessing high-quality records of the ice extent. They used three different sets of data that record the extent of ice in the region.

In terms of attribution, the authors looked for “fingerprints” of human activity. Humans emit greenhouse gases that trap heat. We know that and we have known that for a long time. Greenhouse gases make the Arctic warmer. But, other things are happening too. There are natural changes to the Arctic. There are also other human pollutants that affect the ice. For instance, humans emit small particles called “aerosols” that can get into the atmosphere and block sunlight. So, these human aerosol emissions can actually cause cooling. 

The authors concluded that the combined cooling effect from human aerosols was detected in all three datasets of ice. That means, it didn’t matter whose measurements you used – the effect of aerosol cooling was present. 

So how much of an effect do aerosols have? It turns out 23% of the warming caused by greenhouse gases was offset by the cooling from aerosols. Unfortunately, this isn’t good news. It means that if/when humans reduce our aerosol pollution, the warming in the Arctic and the ice loss there will be worse.

Read the rest of the article here (I get quoted at the end of it!).

As we approach the final stretch...

For years we've talked about one of the most fascinating phenomena of Arctic sea ice loss as it progresses from year to year: The moment when the ice disappears regardless of the weather. We've seen some of that, back in July 2012, when extent and area numbers kept going down steadily, even though weather conditions weren't conducive to melt and should have caused a marked slowdown on the graphs (like they did in the preceding years). Some time later I concluded that this had to do with what I now call melting momentum.

The idea is that if during May and July the ice gets hit by lot of sunshine, lots of melt ponds form and they soak up a lot of heat. This doesn't immediately cause the ice to melt, but starts to make itself felt towards the later stage of the melting season. The built-up momentum keeps the melting going. For this reason I've been focusing on things like compactness, that tells us something about the amount of water within the ice pack, whether open water or melt ponds (satellite sensors can't see the difference).

But does this still hold true? Will there be a moment when the ice disappears regardless of melting momentum as well? We saw in 2016 that there wasn't much melting momentum built up during May and June, but despite the cloudiness, a record warm winter and persistent high air temperatures were enough to make the ice vulnerable enough for a big cyclone and massive dipole to have 2016 come in second on almost all graphs (see this overview). Yes, melting momentum is important, but there are other things at play as well, of course.

NSIDC Compactness (are divided by extent) as of July 29th

Now, this year has been extremely interesting so far. For the third time in a row, the winter preceding the melting season was relatively mild, the maximum was low (second lowest on record), and the trend line on many a graph went low from the get-go. Not as low as 2016, but low. However, as in previous years, clouds moved in and things slowed down to a crawl, taking the trend line as high up as 11th lowest on record on the JAXA sea ice extent chart last week. But then this happened in the last couple of days, suggesting spectacular melting on the Pacific side of the Arctic:

So, what's going on?

PIOMAS July 2018

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.

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PIOMAS June 2018

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:

PIOMAS May 2018

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:

The maximum for sea ice volume was reached during April. According to the PIOMAS model, it peaked on April 16th at 22,376 km3, which is the second lowest maximum on record, 1594 km3 above last year's stunning record low maximum, and 301 km3 below 2011's maximum. The total freeze during the 2017/2018 freezing season was the highest since 2013, but not all that much above the 2006-2017 average. This bar graph shows total freeze for the 2006-2018 period:

So, that's the maximum. After the maximum was reached, the trend line flattened, with sea ice volume going down by a meagre 91 km3 from the 16th to the end of the month, which can clearly be seen on Wipneus' version of the PIOMAS graph:

PIOMAS April 2018

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:

March 2018 turned out to be quite cold, relatively speaking (more on that below). And thus, as expected, volume increased by a lot, especially given that it was relatively low at the end of last month. In fact, with 2278 km3, sea ice volume growth during March was the largest in the 2007-2018 period, well above the average of 1832 km3. This means that the gap with 2017 has widened again, whereas the difference with all other years has become smaller. 2011 is now hot on this year's tail, being just 217 km3 behind. I expect this year to end up having the second lowest maximum on record, but you never know.

Here's how the differences with previous years have evolved from last month:

The 2018 trend line can clearly be seen moving back towards the pack on Wipneus' version of the PIOMAS graph:

Naturally, the trend line on the PIOMAS sea ice volume anomaly graph has shot up, moving away from the linear trend line again, meaning volume loss is slightly less than expected, if one were to extrapolate the data average into the future:

Bering goes extreme

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:

The 2018 melting season has started

For a while it looked like the record for lowest maximum was going to be broken for the third year in a row, especially after an extreme warm event shook the Arctic. But this anomalous heat was followed by anomalous cold, which was just enough to nudge JAXA sea ice extent above last year's record low maximum. By 13 thousand km2, to be precise, which is around 0.1% of total sea ice this time of year.

I don't mind, as I correctly guessed both this maximum's date as well as the final number on Arctic Sea Ice Forum polls, probably for the first (and last) time in my life as an Arctic observer, as the maximum is incredibly difficult to pinpoint.

Here's the best visual representation of maximums throughout the years, produced by ASIF member Hautbois, as it shows when the maximum of a given year was reached, as well as how high it got:

Not a record low maximum, but the fourth maximum in a row that has ended up (well) below 14 million km2. That's for JAXA sea ice extent data (formerly known as IJIS, now provided by ADS-NIPR).  The NSIDC has just reported that for their SIE product this year's maximum was also second lowest on record.

Looking at how much sea ice extent was created since the last minimum (total freeze), this past winter ended up fourth lowest since 2006. Of course, back in the day, minimums were higher than they are now, which meant there was less 'room' for re-freezing:

Here's the spectacular drop from anomalously warm to anomalously cold on the DMI 80N temperature graph, which normally isn't all that representative for the Arctic as a whole, but in this case it is: