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:
It's no surprise 2017 is still lowest on record, according to the PIOMAS model. If during the last week of April the Arctic wouldn't have cooled down (somewhat) like it did, the gap with previous years would've grown even bigger. But as it is, things haven't changed all that much since the end of March. The lead over number 2, 2011, has decreased from 1731 to 1642 km3. The difference with record low year 2012 (at the minimum) is practically unchanged.
Here's how the differences with previous years have evolved from last month:
The annual maximum was also reached in April and I will discuss it below, but first want to go through the usual graphs shown in this update. Starting with Wipneus' version of the PIOMAS sea ice volume graph showing more details:
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):
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):
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:
The lowest point has been reached on all sea ice area and extent graphs, and so the melting season has ended. I'll have more on the details later this week, but here's a quick preview of one of the most important features of this melting season, and that's the decimation of multi-year ice (MYI) on the Pacific side of the Arctic.
Here's a nice video that shows how the melting season developed and ended, based on AMSR2 data. It's made by Felicia Brise of the University of Hamburg, and I've taken the liberty to upload it to YouTube:
There's a stunning contrast between the destruction on the Pacific side of the Arctic, and the relative stable and compact situation on the Atlantic side of the Arctic, even though the ice there was thinnest at the start of the melting season. In fact, this region of first-year ice was so large that it even covered the North Pole, perhaps for the first time on record. I even speculated in my 2014/2015 Winter analysis that under the right conditions the North Pole could become ice-free this year.
But the opposite happened, the first-year ice on the Atlantic side was spared (there was also remarkably little transport of ice through Fram Strait) and it was the multi-year ice on the Pacific side that took barrage after barrage of warm, sunny weather. Now that the ice age distribution maps (developed by J. Maslanik and C. Fowler, and currently produced by M. Tschudi of CCAR) have been updated, we can see how things have proceeded since my last blog post on the subject three weeks ago:
As expected, all of the 5+-year old ice on the Pacific side of the Arctic has disappeared in truly spectacular fashion. As there wasn't that much 4-year old ice to begin with, there will be less of the oldest class of ice next year. On the other hand a lot of the 3-year old ice (green) will become 1 year older, and as said, first-year ice (dark blue) got off lightly.
Nevertheless, it seems that part of the rebound in MYI that happened since 2012 has been wiped out (something I speculated about almost two months ago in this guest blog for the Guardian Environment page). We'll know how much exactly when the NSIDC puts up their monthly analysis two weeks from now. Of course, ice age doesn't necessarily tell us how thick the ice is - this isn't our (grand)fathers' Arctic anymore - but it gives us an idea of long-term changes in the Arctic.
Another indicator is sea ice volume, both modelled and observed. To know whether 2015 will dip below rebound years 2013 and 2014, we'll also have to wait a week or two for the PIOMAS model to be updated. Either way, yet another fascinating melting season is now behind us. Thanks for watching.
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:
If you want to know where you're going, it helps to know where you're coming from. This also goes for Arctic sea ice. Even though the long-term trend is down, it's difficult to tell what will happen in any given melting season. Two things can help us get an idea: initial sea ice state and subsequent weather conditions. This post is about how the sea ice has fared throughout the freezing season and what shape it was in last month when sea ice growth slowly came to a grinding halt and winter started to make way for spring.
For that I'm going to compare the 2014/2015 freezing season with those of the preceding three winters, just like I did last year. That way we can see how the past winter compares to the winters preceding the 2012 record smashing melt and the two rebound years following it. If you want to compare some of the images below with other freezing seasons, you can dig through the 2011/2012 and 2012/2013 winter analyses. And click on the images if you want to have a closer look.
Ice age
We kick off with the AARI ice age maps for the end of April that show the amount of multi-year ice (MYI) in the Arctic (brown colour):
Last year's genetically modified rat has been replaced by a woolly mammoth (I'm sorry, I can't help but seeing animals in these maps), but the amount looks about the same. What is interesting this year is that the MYI looks a lot more fragmented on the Pacific side of the Arctic, with some young ice (pink) and even open water in the Chukchi Sea.
This has everything to do with a cracking event that took place a couple of weeks ago. It wasn't as spectacular as the cracking event of February/March 2013, but it was still quite big, and more interestingly, it took place at the very end of the freezing season. We have to wait and see if there's any consequence for the melting in this region. On the one hand there's a lot of first-year ice (FYI) between the MYI floes which could melt out early. On the other hand heat might be released to the atmosphere, cooling the water below the ice, making it more resistant to melting.
Either way, it's visible on different maps, such as the ASCAT radar images. Here's a comparison for day 109 (April 19th):
With another interesting freezing season behind us, it's time to compare to previous winters and get an idea of this melting season's foundation. As we have seen in the last two years, the start of the melting season plays an important role, and so it might very well be that the end of the freezing season plays a role as well (what holds for the Arctic summer often is the opposite during winter). If only for the fact that the end of the freezing season is immediately followed by the start of the melting season. Sorry for being so simplistic.
OK, we'll repeat the format from last year and compare the 2013/2014 freezing season with three other freezing seasons. In this case, I have chosen the last three winters (ie preceding the 2011, 2012 and 2013 melting seasons). No 2007? No 2007. I know it's blasphemy, but we have to move on. Click on the images if you want to see a larger version.
Ice age
It's clear that after last year's 'rebound' the Arctic now contains a lot more multi-year ice than in the last 3 years, as can be clearly seen on these AARI ice age maps for the end of April:
2011's vomiting cow doesn't look all that smaller (the brown colour represents the multi-year ice), but this year's genetically modified mouse is still a tad bigger, with a large bulk of multi-year ice taking up position in the Beaufort and even some of the Chukchi Sea. Whether this will prove to be a protective barrier, as witnessed in 2010 and 2011, remains to be seen.
These ASCAT radar images also show that this year the ice pack contains a lot more whiter ice. Here's a comparison for day 109 (April 19th):
The melting season is about to shift one gear higher, and so I thought it'd be useful to have a comprehensive look at this past winter (just like we did last year). As we saw in this recent PIOMAS update, it seems that this year's conditions for ice formation were better over on the Siberian side of the Arctic.
The Beaufort Sea had relatively little multi-year ice flowing in which should make the pack weaker there, as evidenced by the large cracking event of February and March. The image on the top right shows a map of the ice pack, where this year's thickness is compared to last year's (red = thicker, blue = thinner).
I want to look further into this by comparing the 2012/2013 winter with those of previous record years, such as 2006/2007, 2010/2011 and 2011/2012. Click on the images if you want a larger version.
I'm starting this blog post off with a conclusion that was reached a while back already: sea ice on the Atlantic side of the Arctic looks vulnerable, sea ice on the Pacific side should be thicker.
Right, with that out of the way we can now look at various aspects of the 2011/2012 freezing season, and compare them to previous years, to be precise the previous freezing season of 2010/2011, and the freezing seasons leading up to and following that other record year: 2006/2007 and 2007/2008. Simply put: I'll be comparing 2007, 2008, 2011 and 2012 before their respective start of the melting season.
I'll try not to use too many words, but I'll be using a lot of images. Click on them images if you want a bigger version.
Ice age
I'll start with the AARI ice age maps. These images are for the end of April, and they look upside down, because it's from the perspective of the Russians who produced them:
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