Arguments
Has Arctic sea ice returned to normal?
What the science says...
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Thick arctic sea ice is in rapid retreat. |
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Climate Myth...
Arctic sea ice has recovered
"Those who have been following NSIDC and JAXA sea ice plots have noted that this has been an extraordinary year so far, with Arctic sea ice hitting the “normal” line on some datasets. ...
As of today, JAXA shows that we have more ice than any time on this date for the past 8 years of Aqua satellite measurement for this AMSRE dataset." (Anthony Watts, 22 April 2010)
At a glance
One of the great metrics of climate change, because it is easy to visualise, is sea-ice in the Arctic. Every year, the ice margins retreat in the northern summer, reaching a minimum extent some time in September. It then refreezes through the long, dark cold winter months, until its maximum extent is reached in March.
Arctic sea-ice has a seasonal component - so-called 'first year ice' - and the more perennial 'multi-year ice'. First-year ice is relatively thin - 30-40 centimetres is typical. Multi-year stuff is thicker - 2-4 metres and much of it is situated between the north coast of Greenland and the North Pole.
Most of the annual, seasonal decline in ice extent, observed by satellites for more than 40 years, is due to first-year ice melting: the more robust multi-year ice takes more energy to remove, but nevertheless it is in decline, too. Calculations of sea-ice volume reveal that trend.
How does sea-ice form? We all know the freezing temperature of saltwater is lower than that of freshwater, hence the spreading of rock salt on the roads on frosty winter nights. Similarly, the ocean temperature needs to fall below -1.8°C (28.8°F) for sea-ice to form. In the freezing season it starts freezing over once the upper 150 metres or so of the ocean are close to that temperature.
Melt varies a lot from one year to another. This should come as no surprise: sea-ice, being on an ocean, moves about a fair amount. Variations in ocean-currents are particularly important since if sea-ice can be 'exported' out of the Arctic, it enters what is basically a hostile environment, where it melts away to nothing. Incidentally, such floes are a lot smaller than icebergs like the one that famously destroyed the Titanic in April 1912. Such ice behemoths originate where glaciers 'calve' upon reaching the sea.
Weather is a highly variable driver of sea-ice melt. Prolonged strong winds from the right direction can cause mass-export of ice into warmer waters. Then again, winds from the south transport warm air over the Arctic Ocean, causing the melting to intensify. But they may also bring in extensive cloud-decks, blocking a lot of incoming Solar energy. No surprise then that melt seasons vary a lot from one season to another.
As in most things related to climate change, it's the multidecadal trend that is key and that is unequivocally downwards, both in terms of extent and volume. Sudden spurts of growth are interesting, as are record meltdowns such as that in 2012. But that's it. Trend is the critical bit. The data clearly show that since 2010, when the statement in the box above originated, eight out of the ten lowest Arctic sea-ice minima have occurred. The only two melt-seasons outside of that time-frame were in 2007 and 2008. For the big picture regarding Arctic sea-ice, ignore the noise from one year to the next and look at all the data. It's heading one way - down.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
Discussions about the amount of sea ice in the Arctic often confuse two very different measures of how much ice there is. One measure is sea-ice extent which, as the name implies, is a measure of coverage of the ocean where ice covers 15% or more of the surface. It is a two-dimensional measurement; extent does not tell us how thick the ice is. The other measure of Arctic ice, using all three dimensions, is volume, the measure of how much ice there really is.
Sea-ice consists of first-year ice, which is thin, and older ice that has survived one or more melt seasons, so that it has accumulated volume. This thicker multi-year ice is particularly important because it makes up most of the volume of the sea-ice. Volume is also the important measure when it comes to climate change, because it is the volume of the ice – the sheer amount of the stuff – that science is concerned about, rather than how much of the sea is covered in a thin layer of ice*.
Over time, sea ice reflects the fast-changing circumstances of weather. It is driven principally by changes in surface temperature, forming and melting according to the seasons, the winds, cloud cover and ocean currents. In 2010, for example, sea ice extent recovered dramatically in March, only to melt again by May.
Because sea-ice is subject to such powerful short-term effects, we cannot conclude anything about the health of the ice from just a single year’s data. It is over multiple decades that an obvious trend emerges. According to the National Snow and Ice Data Center, the overall trend in Arctic sea-ice minimum extent from 1979 to 2022 is down - by 12.6 percent per decade, relative to the 1981 to 2010 average (fig. 1). The average loss of sea ice works out at about 78,500 square kilometres per year. That's like losing an area the size of the state of South Carolina or the country of Austria - every year!
Fig. 1: Sea-ice extent in a) September, at the seasonal minimum (top panel) and b) March, at the annual maximum (bottom panel), for the period 1979-2023, . The trend is clear. Source: NSIDC
Multi-year ice volume is in steep decline. As you might imagine, thick ice takes a lot more heat to melt, so the fact that it is disappearing so fast is of great concern (fig. 2).
Fig. 2: Arctic sea-ice volume anomaly from PIOMAS. Daily sea-ice volume anomalies for each day, computed relative to the 1979 to 2022 average for that day of the year. Tick–marks on the time axis refer to the first day of each year. The trend for the period 1979- present is shown in blue. Shaded areas show one and two standard deviations from the trend. Error bars indicate the uncertainty of the monthly anomaly plotted once per year. Source: Polar Science Center, University of Washington.
It is clear from the various data sets, terrestrial and satellite, that both the sea ice extent and multi-year ice volume are reducing decade by decade. The full extent of annual ice reduction is seen in September of each year, at the end of the Arctic summer, and is on a long-term downward path. Multi-year ice volume has not recovered at all, and is showing a steeply negative multidecadal trend.
* Footnote: Although a thin layer of ice doesn’t tell us much about the overall state of ice loss at the Arctic, it does tell us a great deal about Albedo, the property of ice to reflect heat back into space. When the sea ice diminishes, more heat passes into the oceans. That heat melts the thick ice and speeds up the melting of thinner sea ice, which in turns allows more heat to accumulate in the oceans. This is an example of positive feedback.
Last updated on 4 February 2024 by John Mason. View Archives
Just saw some great news about significantly increasing multi-year arctic ice! (2014 compared to 2013 and previous). Hopefully we will see a continued gain in "older" (2-4+ year old ice) ice extent. nsidc.org/arcticseaicenews/files/2014/04/Figure5-350x618.png
Juan_H... It's nice to be optimistic but this is unlikely to be anything more than a temporary change. We're still likely looking at seasonally ice-free conditions starting around 2030.
It's just that, on the way to the bottom the numbers are going to bounce around like this.
Note that the NSIDC states along with the graphic Juan presented...
"The percentage of the Arctic Ocean consisting of ice at least five years or older remains at only 7%, half of what it was in February 2007. Moreover, a large area of the multiyear ice has drifted to the southern Beaufort Sea and East Siberian Sea (north of Alaska and the Lena River delta), where warm conditions are likely to exist later in the year."
There's an interesting post or two by Tamino noting that ice variability greatly increased around 2007 - smaller amounts of ice are simply going to be more affected by yearly weather.
The 'significant increase' seems to have gotten us back to ~ March 2008 multi-year ice levels... yet PIOMAS shows that after the 'high' ice volume at the end of last summer's melt, the final March 2014 volume was lower than every previous year except 2011.
That seems contradictory... until we consider that the multi-year ice chart shows percentages. The percentage of the ice which is now multi-year is similar to what it was in March 2008. However, the total amount of ice has decreased and thus the 'same percentage' actually means less multi-year ice. This can also be seen on the PIOMAS average ice thickness graph. There, 2014 is higher than all years since 2008, but significantly below 2007. The average thickness has increased because the percentage of thick ice is higher while the total ice volume has declined.
Volume will always be the determining factor because it quite simply is the amount of ice. The fact that the volume at the end of March 2014 was slightly lower than that of March 2012, which went on to have the lowest summer volume (and extent) ever, tells me that there has not been any 'recovery' in sea ice. We are at essentially the same place we were in 2012. Thus, if we again see weather conditions like that year we could again see new record lows this year. If we get better weather conditions maybe we'll start to see an actual recovery in a few years, but it clearly hasn't happened yet and doesn't seem likely to as the planet continues to warm.
Interesting aside: When nearly all of the sea ice has melted out, the last remaining bits will be large 'ice islands' of very thick ice broken off from land. At that point, the 'multi-year ice' in summer will be near 100% while the ice extent and volume will be near zero.
I suspect that in the upcoming years we'll see a trend of growing percentages of summer multi-year ice (and average ice thickness). Not because the ice is 'recovering', but simply because the thicker multi-year ice will be the last to go.
CBD,
Broken off glacier ends called ice islands and ice bergs are not sea ice, they are land ice. If they are the only ice left than sea ice extent is zero. The extent of these ice islands is very samll, even near Greenland.
jetfuel, so what if anything is up from year to year? In the 35 years of the satellite record for ASI area, area at minimum exceeded the previous year's minimum fifteen times, yet the overall trend is strongly negative. If this year's minimum drops below last year's, what will it tell us? Very little. Just as 2013's increase at minimum over 2012 told us very little. As for multiyear ice, there's so little left--like volume--that variance can be played up into quite a rhetorical pudding: "multi-year ice has doubled over last year!"
Please do not respond to any future comments by jetfuel until a Moderator has had a chance to ascertain whether or not it is in full compliance with the SkS Comments Policy. From here on out, jetfuel is on a very short leash. His/her shennanigans will be stopped one way or another.
per nsidc: "The multi-year ice in the Arctic Basin increased from 2.25 to 3.17 million square kilometers during the year.
Multi-year sea ice made up a total of 30% of the Arctic icepack the previous compared to 43% this winter." (2014)
Also from another nsidc article: "It was the sixth-lowest extent recorded since satellites began measuring sea ice in 1979. The number is above the 2012 record extent but is still below the long-term average. "
3.17M out of the 5.02M min for 2014 is 63% of remaining ice being multiyear ice. 3.17M of the 2014 max of 14.9m is 21.3% multiyear ice. The 7% number is stale news as of today. Out of the last ten years, only one year, 2006, had more min sea ice worth mentioning than 2014. Any trend line drawn for the last 2-8 years shows upward trend in Arctic minimums, if it accounts for 2012 as being an anomolous year due to rare wind storms that caused unusually high melting by pusing huge sections of sea ice south. Throw out that datapoint or bump it up to 4.4M and the trendline is unquestionably upward since summer of 2007. It appears as though we are headed more towards another 5.0M+ min next year, making it a 9 year upward trend in Arctic SI mins. At what point can we call this a turnaround? At what point do we stop being so confident that the Arctic will be seasonally ice free by 2030? Not when 8, going on 9 years are pointing the other way? My guess is that 9 years won't be enough to quiet the 2030ers.
[JH] Future posts of this nature will be summarily deleted.
[PS] Jetfuel, you have had cherry-picking explained to you. You were invited to respond if you didnt understand. Your continued use of cherrypicking as an argument would imply either wilful ignorance or trolling. Moderator tolerance is at the end.
jetfuel... Them's bettin' words! I'd put $100 on seeing a new Arctic sea ice minimum within the next 3-5 years.
Do you really not understand the difference between the two sides here, jetfuel? You're taking a small group of data points – isolated from any science – and are trying to extrapolate what you would prefer to see happen.
The other side is looking at science. We're looking at what's been happening over the past 150 years. We're looking at the changing radiative forcing of the planet. We're looking at interconnected climate systems with ocean/atmosphere/land/ice, and hundreds of other factors.
When you look at all these things combined you get exactly one answer relative to Arctic sea ice: It's going away and, at this point, there is nothing we can do about it. Even the oil companies know this and, in a very sad irony, are spending lots of money planning how to drill the Arctic ocean.
You can play around with Excell and make plots for what you want to believe, but it's wrong. There is functionally zero chance that Arctic sea ice is going to see a recovery to anything like we saw 20-30 years ago.
I would almost be willing to bet that we'll see initial ice free conditions (defined as <1M/km2) within the next ~5 years.
jetfuel - Let's see, insufficient data to establish trend significance (2-8 years, check)? Cherry-picking established.
Tamino had an interesting post in 2012, Sea Ice Forecasts, noting that Arctic ice extent statistics demonstrated a change in 2007 - with an amplified annual cycle, more year-to-year variation than before. This change persists today with yearly swings in extent averaging larger than previously observed. A reasonable understanding of this change is that the much reduced ice volume and thickness has made Arctic ice extents more susceptible to wind/weather effects than earlier, thicker ice.
Meanwhile, ice volume continues to decrease.
[Source]
jetfuel, you're cracking me up. You toss out 2012 but don't toss out 2007 for similar reasons. Why? Because if you did, you'd have no "recovery" claim. Instead, the long-term decline would be even more obvious, and 2013 would look like a normal year in that long-term trend. Your logic is identical to the "no warming since 1998" logic, and it's just as goofy.
I wonder: did you run the same analysis after 2007 and conclude that science had massively underestimated future sea ice loss and that the Arctic would be ice free at summer minimum within three years?
[Moderator's Comment] All: Three repsonses to jetfuel's nonsensical comment #59 is quite enough. Dog-piling is a prohibited by the SkS Comments Policy.
Interested party,
You would be better off studying climate science that chaos theory when you want to comment on a climate board. The natural trend now is cooling. Without human influence the temperature would be cooler. Your general comment seems to suggest it is impossible to know anything. Scientists feel we can learn and project what needs to be done.
Perhaps you can sugggest a specific topic you want to discuss and we can help you figure out what you want to learn.
interestedparty... "...to comment on the obvious."
Therein lay the problem. You don't have to be an expert but you would need to have a little bit of humility regarding a complex field outside of your own when it comes to understanding what is, and what is not, "obvious."
What, pray tell, would you think is so obvious that specialists in the field have failed to already consider and include in their overwhelmingly agreed upon positions regarding man-made causation of global warming?
Interestedparty... I would highly suggest you read the SkS commenting policy before posting any further.
[PS] It would seem that Interestedparty does not have the slightest interest in abiding the comments policy.
There's a BBC story today about a paper by Rachel Tilling to be presented at the AGU. She mentions "a decline that looks a bit like a sawtooth, where we can lose volume but then recover some of it if there happens to be a shorter melt season one year". Unfortunately the news story doesn't make it clear what the period of this sawtooth would be. The minimum this year seems to have recovered nearly to 2009 levels, but the longer-term trend is still towards an ice-free Arctic summer by the 2020s, as shown in ArctischePinguin's graphs here.
alan2112drums:
Further to your comment on the Antarctic thread, please see the original post and review the findings on sea ice.
You may also wish to review the behaviour of the sea ice relative to the IPCC AR4 projections (here) - note that this information is only from 2009, so it doesn't show the record low set in 2012 - or the behaviour of the sea ice over the last (not quite) 1,500 years (here).
Basically, Arctic sea ice has fallen off the proverbial cliff. Al Gore got that right, at any rate.
Arctic sea ice minimum in 2014 (September) was 5.02 million km², which NSIDC reports is the 6th lowest on record. Arctic sea ice maximum in 2014 (March) was 14.8 million km², which NSIDC reports is the 5th lowest on record.
Arctic sea ice behaviour year-over-year is not monotonic, and as far as I can see the Daily Mail is taking advantage of this fact to form a narrative that casts doubt on the science, when in fact what is seen is merely the result of stochastic fluctuation.
Just to be clear, what I perceive the Mail as doing is:
In reality, Gore echoed Wieslaw Maslowski's prediction.
Maslowski's prediction, originally made in 2006, was that Arctic sea ice would decline to <1,000,000 square kilometers extent (with no ice at the North Pole) by the end of the September melt by 2016, +/- 3 years. So 2013-2019. [Source, slide 6]
But that truth is always inconvenient to deniers, who revert to their preferred idiom of mendacity, prevarication and lies indiscriminately, without pretext needed.
Responding to off-topic comment here (as is #68 & #69 above).
The David Rose item in the Rail on Sunday of 30/8/14 basically does the usual Rose trick of "hiding his bogus decline" in AGW predictions by making such predictions as extreme as possible and then proving them to be in error. Sadly, and Rose is a real saddo, he is unable to do this without misrepresenting those extreme positions and his proofs.
To debunk his 30/8/14 piece would take a while to write out. But it would likely start something like this.
☻ Rose misrepresents what Gore said in 2007. Firstly Gore was reporting what others had said and secondly he mentioned two predictions for an ice-free summer - 7 years and 22 years. Rose usually plays an extremly strong game misrepresenting AGW comment.
☻ The 25th August date is a bit of a cherry-pick. A couple of days earlier and it would have been "since 2009" not since "since 2006" because 2009, 2013 and 2015 SIE were very similar through the height of the melt season.
☻Rose mischaracterises the period 2012-14. Most of the SIE increase (90%) occurred 2012-13. His comment about 'consentrations' is likewise a mischaracterisation. Most of the SIA increase (95%) occurred 2012-13. So his news story is a year out-of-date. SIV is however more even between the two years.
☻ Judy Curry is more a denialist blog-mom these days and no longer a pukka climatologist. Her assertion that the "death spiral" is (or will be) entering a reversal which will last decades is air-headed lunacy of her own creation.
And on and on and on.
Just caught this on Yahoo earlier:
Link to Mashable article
[DB] Link truncated.
Quantummist,
Your quote from NSIDC is interesting. I wonder why you picked a quote from Feburary 2014 istead of a more recent quote.
This years NSIDC report did not mention the CRYOSAT data. Nevin has a good article on the January 2015 PIOMAS data here. PIOMAS and CRYOSAT usually agree. The data does not really have anything unusual to report. Perhaps next week when the new PIOMAS data comes out it will be more interesting since, as the moderator pointed out, Arctic sea ice is currently at it's all time low for the date.
michael sweet @72, perhaps more interesting is the Cryosat data, which for the most recent update (Dec 15) showed reduced ice volume relative to 2013:
At that time, Piomass was showing the ice volume to have been the largest since 2008, whereas Cryosat ranked it fourth in its five years of observation. The drop in volume relative to last year is more consistent with the sea ice extent figures, as linked by moderator PS:
As of today, NSIDC's Charctic graph is showing 2015 as the lowest SIE on record having just dipped below 2006. JAXA, who show a less icy 2006, put 2015 well below 2006 & 2011.
Mind, the timing of the maximum freeze is a little delayed nowadays compared with the climatology in the graph @73 so there is still a couple of weeks for things to change around.
Re @73 & @74 - A whole range of Arctic sea ice metrics, now including Cryosphere Today area and DMI extent, are currently at their lowest ever levels for the date in their respective historical records:
Arctic Sea Ice Area Lowest Ever (For the Date!)