Arguments
Human activity is driving retreat of Arctic sea ice
What the science says...
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Thick arctic sea ice is undergoing a rapid retreat. |
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Climate Myth...
Arctic icemelt is a natural cycle
"In 2007, the Northern Hemisphere reached a record low in ice coverage and the Northwest Passage was opened. At that point, we were told melting was occurring faster than expected. What you were not told was that the data that triggered this record is only available back to the late 1970s. We know the Northwest Passage had been open before." (Matt Rogers)
At a glance
The Northwest Passage is the sea route around the waters off northern Canada and Alaska. Its discovery and eventual navigation involves a fascinating tale of endeavour, adventure and tragedy, too, for some expeditions ended in disaster.
Of the many mishaps, by far the worst was that which befell Sir John Franklin and the 128-strong crews of his two ships: they were last heard of in 1845. It took many expeditions and almost ten years before their fate was finally pieced together. One thing became clear by then: the Northwest Passage does not take prisoners. Yet at the same time, those searches for Franklin and his crew generated lots of new chart cover of the waters between the islands making up the Canadian Archipelago.
Complete navigation of the Northwest Passage was finally accomplished by Norwegian explorer Roald Amundsen between 1903 and 1906. Amundsen's boat was relatively small at 47 tons and 70 feet long but usefully it had a very shallow draft. That meant it was able to pass through areas where a bigger boat would have fouled the bottom, thus offering a wider choice of courses to take. Amundsen's route was criticised in some circles because of that factor - what was the point of making the crossing if bigger freight ships could not? But Amundsen was motivated not by money but by science.
With his experienced crew of six, they spent two winters off the eastern side of King William Island, about halfway through the archipelago, collecting data on Earth's magnetic pole and local meteorology, traded with the Inuit and developed hunting and fishing skills. Leaving there in August 1905, they reached Nome, Alaska twelve months later. The ice had pinned them in for a third winter. There was not to be a single-season crossing for another 38 years, when Sergeant Henry Larsen of the Royal Canadian Mounted Police managed it in a schooner.
So yes, while the Northwest Passage was successfully navigated before 2007, the current state of the sea ice means that the picture is now quite different. Part of the reason for that is down to the age of much of the Arctic sea ice today. Sea ice that has yet to experience a summer melting season is known as first-year ice. It's relatively thin, fragile and more vulnerable to melting compared to the ice that has withstood one or more melting-seasons, known as multiyear ice. Multiyear ice can even give a good ice-breaker a run for its money. But now there's a lot less of it.
During many recent summers the Northwest Passage has become open: freight ships and even cruise liners have steamed through. That doesn't mean it's risk-free of course - there are still icebergs to watch out for. Nevertheless, it's getting to the point where there are various concerns being voiced about the number of ships passing through the area, on both ecological and political grounds. For the Northwest Passage, global warming really is a mixed blessing.
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
Arctic sea ice has aptly been termed a "canary in the global warming coal mine". In other words, it is regarded as a sensitive indicator of manmade climate change. Because of that importance, climate science deniers will often attempt to fob off the decline of Arctic sea ice as a natural phenomenon.
Satellite measurements of Arctic sea ice extent (fig.1) reveal a rapid decline over the past 45 years, particularly at the end of each year's annual melt season. The downward trend and the increasing difference between seasons are both in keeping with predictions of the effects of global warming.
Fig. 1: Monthly sea ice extent anomalies (solid lines) and linear trend lines (dashed lines) for March (black) and September (red) from 1979 to 2021. The anomalies are relative to the 1981–2010 average for each month. Image: American Meteorological Society State of the Climate 2021 (index here).
As the Arctic warms, the volume of ice in the region gradually declines. In particular, the thicker multiyear ice that used to be present in abundance has declined significantly (fig 2). Instead, today's ice-pack is dominated by first-year ice that is far more prone to seasonal melt. Combined with natural factors such as storms, this vulnerability can sometimes produce huge melt years such as 2012's record-buster.
Fig. 2: The age of the ice pack—which has been observed since the 1980s is used as a proxy for ice thickness. In mid-March 1985 (left), the winter maximum ice pack was dominated by ice at least 4 years old (white). In 2021 (right), only a small strip of very old ice remained tucked up against the islands of the Canadian Arctic. More than half of the winter ice pack was less than a year old (dark blue). NOAA Climate.gov image, based on data from the National Snow and Ice Data Center. Original can be found here.
So, how can one expect climate science deniers to claim all of this melting is simply natural? A popular misinformation-technique is to state that we are just seeing the effects of multidecadal natural cycles causing deep swings in Arctic sea ice coverage and volume. Direct observational support for such 'cycles' is of course impossible. Convenient, eh? Since 1979, we have relied upon direct observations of sea ice extent with contemporary instruments aboard satellites. That's not a long time in the grand scheme of things. What about before then?
In fact, thanks to ocean sediment cores and other physical clues left behind by past climate regimes, we do have pretty good insight into past Arctic sea ice extent. Combining various sources of information about past climate behaviour, we can figure out why changes in ice coverage have occurred in past times.
Natural climate variations have indeed caused significant changes in past Arctic ice extent. Of course they have. But it's important to remember that such changes in no way constitute airtight arguments against modern ice-loss being contributed to by anthropogenic global warming. Events of the pre-industrial past obviously had other causes. Today's losses of sea ice can in contrast be partly attributed to our disruption of the Carbon Cycle through fossil fuel-burning. Indeed, comparisons between past and present Arctic climate reveal different reasons for past and modern sea ice changes (Overpeck et al. 1997). Meanwhile, analysis of several hundred markers of past Arctic sea ice extent tells us that recent losses appear to have no parallel in records going back many thousands of years (Polyak et al. 2010).
Evidence from the past two hundred years shows how natural and anthropogenic influences on Arctic sea ice can be distinguished. Data demonstrate that the Arctic underwent an unusually cool period in the early 19th century. That was followed by recovery to milder conditions extending all the way into the 20th century. After the middle of that century, we see the accelerated warming of recent decades. This pattern is in good agreement with other observations of global warming such as increasing air and ocean temperatures.
It is worth saying again: both observations and model simulations indicate that the nature of the Arctic warming in the last two decades is distinct from the early twentieth-century mild period. Recent, additional reductions in Arctic sea ice are mostly caused by a new, anthropogenic mechanism (Johannessen et al. 2004) and are thus unique in Earth's history.
Last updated on 25 February 2024 by John Mason. View Archives
[DB] "Those "ice loss is accelerating" claims based on short time frames need to take this into consideration."
Short time frames...you mean like that covering the entire satellite record, perchance?:
Or this, hiliting that climastrological seasonal cycle?:
[Source]
So, when we've endured 316 317 consecutive months of global temperatures above the 20th-Century average (the last cooler-than-average month was Feb 1985), and the Arctic Sea Ice trends are linearly to greater-than-linearly down (that Arctic Amplification thingy), where's the recovery for crying out loud?
Regular readers are surely noting the zeal displayed by those that seize upon every last vestige of hope to deny the obvious: recently the world is warming due to human activities (fossil fuel derived CO2), and the Arctic Sea Ice is in a downward spiral as a result.
I repeat: only Maslowski's model comes anywhere close to replicating the metric-ed trend observed in the Arctic. And his model predicts a summer minimum with mostly-ice free Arctic Ocean by 2016, ± 3 years.
But by all means, that's only natural...
[DB] The AO is what it's name says it is: an oscillation. Thus, the long-term trend is nil. But the reality shows that what is happening in the Arctic is indeed unlike a natural cycle and fits the understanding of the Arctic Amplification response to the ongoing warming of the world. With the ongoing demise of the Arctic Sea Ice cap serving the role of the canary in the coal mine.
As far as colder air forming a negative response to the amplification, see:
BOE et.al (2009) "Current GCMs' Unrealistic Negative Feedback in the Arctic", Journal of Climate
H/T to the Artful Dodger.I'm debating a Watt-bot and he's claiming that Arctic ice decline is all due to changes in wind patterns. He's posted several articles, but the broadest claims are made here:
Wind contributing to Arctic sea ice loss, study finds
Anything in the article that points out this doesn't question climate change's role he describes as spin - even though the study itself only seems to attribute 30-50% of the ice loss to changing wind patterns, according to the article.
Apparently this line is the dominant response to Arctic ice loss at WUWT other than the occasional rallying cry of "Recovery" (such as we are currently hearing). Any thoughts on this?
In reference to my own question at #59: in case anyone else encounters this argument, I dug up the answer myself. This is from Joe Romm, and addresses that "single factor" talking point nicely:
Study: “It is clear … that the precipitous decline in September sea ice extent in recent years is mainly due to the cumulative loss of multiyear ice.”
muoncounter#46:
May I know the source of this graph? Haven't been able to dig it up.
PS - sorry, make that Muoncounter#49...
I was reading this the other day:
https://www.rmets.org/sites/default/files/qjcallender38.pdf
It was published in 1938, written in 1937. In the discussion chapter I found this citation:
"Dr. C. E. P. BROOKS said that he had no doubt that there had been a real climatic change during the past thirty or forty years. This was shown not only by the rise of temperature at land stations, but also by the decrease in the amount of ice in arctic and probably also in antarctic regions and by the rise of sea temperatures."
And:
"In reply to Dr. Brooks, the author agreed that the recent rise in arctic temperatures was far too large to be attributed to change of CO he thought that the latter might act as a promotor to start a series of imminent changes in the northern ice conditions. On account of their large rise he had not included the arctic stations in the world temperature curve "
There seems to have been a large melting during possibly up to 40 years where there was a local warming of both land and sea, melting large amounts of ice. The strange thing is that there seems to have been a 10-fold increase in temperature in the polar area compared to lower latitudes.
I thought this was a cool period and I don´t find anything in the graphs for temperature in the 19th century representing that increase which should have started 1900-1910. I´ve never seen it mentioned anywhere but in this article and old newspaper. I thought that the warming started later.
Bu the most interesting detail is that there was such a large difference between the polar region and lower latitudes. We don´t see that now as the ice is melting.
It indicates that we are missing something about polar ice melting. Are there any similar differences today? Are there any areas experiencing 10-fold temperature increase compared to other areas?
I guess that there is no way of investigating the extent of melting back then, but the small bits of information i have found indicates that it was much larger than today. Even if it was smaller or the same extent, it is confusing that there was such large melting during so many years during a period where data says the global mean was low.
Since the polar region doesn´t show a larger increase in temperature than other areas, and certainly not a 10-fold increase, maybe we don´t have that much to worry about, at least when it comes to polar ice?
Seroius and I think well founded question here.
In the source linked, http://nsidc.org/cryosphere/sotc/sea_ice.html they describe that antarctic ice has been increasing during this time period while arctic is decreasing. In terms of standard deviation from mean the arctic decrease has been twice as sharp, but:
1. In terms of volume of ice, are we net gaining or losing ice at the poles?
2. Since arctic ice is floating and antarctic ice is on land (pulling this from Inconvenient truth), should the antarctic ice be the main concern when it comes to rising sea levels? Or is that outweigh by the specific areas growing or shrinking (e.g. growing areas are sea ice, shrinking are land based)?
jfrantz @64, the linked source is describing sea ice for both Antarctica and the Arctic. Antarctica has a fringe of sea ice that is preserved even in summer, though with minimal extent (about 4 million km squared). In winter it becomes very extensive, exceeding in extent the Arctic sea ice maximum, mostly because it can extent into open ocean. In terms of sea ice extent, the reduction in Arctic sea ice has been far greater, as shown in the graph in the section on Antarctic sea ice extent in the linked source. That graph, however, only extends to Dec, 2012. A more recent graph shows the Antarctic sea ice extent anomaly to have declined astonishingly over the last two years, reaching Arctic (and hence negative) levels by Dec 2016:
(Source)
The low extent anomaly has continued into 2017:
(Source)
With regard to sea ice volume, we are primarilly dependent on models, as there are insufficient depth measurements of the ice to provide a region wide, continuous time series.
A region wide model for Antarctic sea ice volume reported in 2014, and showed sea ice volume to 2010:
The trend of 28.7 km^3/yr compares to Arctic trends of -260 km^3/year in April, and -320 km^3/yr in September shown for the Arctic:
Obviously the recent massive retreat in Antarctic sea ice extent will also have been reflected in a retreat in Antarctic sea ice volume, but as we do not know to what extent it has been matched by a reduction in sea ice thickness, we do not know by how much.
Finally, if Al Gore did say that "arctic ice is floating and antarctic ice is on land", that is misleading (at least out of context). The peak Arctic sea ice volume was about 33,000 km^3 in April (the time of maximum volume). That is dwarfed by the 2,900,000 km^3 volume of the Greenland Ice Sheet. Looked at differently, 14,000,000 km^2 area of the Antarctic continent, while five times the minimum Antarctic sea ice extent is about 80% of the maximum Antarctic sea ice extent. Whether we look at either volume or extent, both polar regions are a story of land ice and sea ice. However, Antarctica is landice surrounded by sea, while the Arctic is sea ice surrounded by land. That makes a very large difference with regard to the rapidity of temperature responses, and the rapidity of albedo changes with warming or cooling, both being much faster in the Arctic. With regard to sea level rise, however, both poles are a land ice story.
To sum, the earth is losing a trillion tons of ice per year:
- 159 Gt Antarctic land ice, McMillan el al, GRL (2014)
+ 26 Gt Antarctic sea ice, Holland et al, J Climate (2014)
- 261 Gt Arctic sea ice, PIOMAS
- 378 Gt Greenland, Enderlin et al, GRL (2014)
- 259 Gt other land based glaciers, Gardner et al. Science (2013)
Total = - 1,031 Gt
Losses outnumber gains by a ratio of 40:1
NASA's position on land-based ice sheet mass losses:
Greenland Land-based Ice Sheet Mass Losses, per GRACE:
Antarctica Land-based Ice Sheet Mass Losses, per GRACE:
As Tom notes, both the Arctic sea ice and Antarctic sea ice are more than 2 standard deviations below the long-term average. So that point bears repeating.
Arctic Sea Ice (per NSIDC):
Antarctic Sea Ice (per NSIDC):
If the Arctic Ocean ice cover is continuing to decline the melting season, in the future Are there will have the black sheet which absorb heat causing ice to melt more.On the other hands if the ice is continuing to melting Are it will reach some point to stop melting and gaining ice instead?
The ice movement can cause to loss of ice mass.The loss of ice mass is a key indicator for ice sheet.The major characteristic of the Arctic is the warming faster than the rest of the globe as a result especially in summer.The sea ice retreat has significant effects on high latitude ecosystems on the evolution of climate change itself.How the Arctic icemelt is a natural cycle because one of the reason because human activities?Then human activities cause to effect the climate change.And climate change of Arctic sea ice as natural phenomenon.
If it is a natural cycle then it will not effect only on the land but how about the shortwave radiation in the atmosphere or the Arctic troposphere.Another important feature of Arctic chemistry is the involvement of bromine gas in sudden ozone depletion events in the lower troposphere during spring.However human activities not effect only climate or temperature but it effect to living organisms and their habitats.
If it possible that polar bear immigrate to the other parts of the world because of the environment has changed.Furthermore maybe in the future there will have the technological solution to mitigate the problem that is happening.
Japanese (JAXA), Danish(DMI), US (NSIDC) and US MASIE data show minimum Arctic ice extent has not decreased since 2007.
DMI shows minimum Arctic ice volume has not decreased since 2003 when readings first began, however PIOMAS shows a decrease. One is obviously wrong.
The first IPCC report in 1990 showed sea ice extent from the early Nimbus satellites from 1973 to 1990. (Observed Climate Variation and Change chapter 7) Ice extent grew 500,000 square kilometres from 1973 to 1979 which was probably the highest extent since about 1910.
Ice decreased significantly in the 1920's through to the 1950's and increased until 1979. The current satellite monitoring started in 1979 but if it had started in in the 1920's, it would probably would be about the same as now.
If you look at the Atlantic Multidecadal oscillation index, you will see that there is a close correlation with Arctic ice
Bruce @70 ,
I presume you are talking about Arctic sea ice volume. Ice volume is distinctly more important than ice extent, in showing which way things are trending ~ particularly the summer minimum (for obvious reasons!).
PIOMAS shows a huge decline in summer ice volume over 40 years.
DMI shows the summer minimum volume for 2015 thru 2018 as being below the 2004-13 average. And 2019 YTD is also below the average.
( Sea ice extent in the 1920's and prior, was poorly monitored, for obvious reasons! We won't mention the war . . . or the Titanic. )
Bruce, I must confess I don't see what point you are aiming towards. Please go into details, if possible. Were you leading towards a Pacific oscillation?
bruce @70,
May I add some numerical bones to the comment from Eclectic @71,
DMI Arctic Sea Ice plots the 2016 minimum as being 1.7cukm below the average minimum 2004-13. Using PIOMAS monthly data the 2016 minimum sits 2.2cukm below th 2004-13 average, this not a great difference given the measurements being undertaken. So your assertion that one of these must be wrong requires some explanation.
You further assert that 2007 provides the lowest annual minimum for Arctic Sea Ice Extent in JAXA, DMI, NSIDC & MASIE when all these show the minimum year as being 2012. A plot of rolling 12-month averages (as per the graph in the OP above) shows a reasonably constant reduction in Arctic Sea Ice Extent, from 12.3M sqkm in 1979 to 10.3M sq km today. The lowest annual average Arctic SIE occurred in 2016.
You assert solely on the basis of IPCC FAR Fig 7,20a (below) that 1979 saw "probably the highest extent since about 1910." Fig 7.20a does show a downward wobble in 1974 prior to the satellite era (as does the graph in the OP above) but this is small relative to the reduction in SIE over the satellite era. The 1974 dip, all of 0.3M sqkm, is shown in the graph in the OP above which also shows the reduction in SIE over the satellite era, something not well set out in Fig 7.20a.
Finally, while values for the AMO does have reasonably uncontroversial sources, this is not the case for all sources of 20th century Arctic SIE records. Perhaps you could thus be clear as to your source of 20th century Arctic SIE data.
With the absence of any further comment from commenter bruce, it might be worthwhile joining a few dots to make sense of his intervention @70.
The insistence that Arcric SIE annual minimums have "not decreased since 2007" follows from denialist insistence that there has been an Arctic version of the 'hiatus' - Arctic Sea Ice has not been diminishing as it did in previous AGW years and the trend is now flat. Swart et ak (2015) 'Influence of internal variability on Arctic sea-ice trends' has been cited as showing evidence of this 'hiatus' operating over the 6-year period 2007-13 and which is now assertedly extended for significantly more years. Thus the "not decreased since 2007" is not interested in the 2012 minimum as the denialist assertion concerns the multi-year trend not the individual years.
The data used for IPCC FAR Fig20 is described thus:-
It is obviously not the best of data given it shows such a small drop in SIE 1979-1990. It may be possible to find this data within literature of the time (the likes of say Mysak & Manak (1998) also use some JIC data) but it doesn't in anyway resemble modern satellite SIE data.
The AMO's "close correlation with Arctic ice" is probably simple nonsense. Even denialists like Connolly et al (2017) found it difficult to fabricate an Arctic SIE racord based on Arctic temperature that was much different to more respectable records using similar methods. The graphic below is from Cea-Pirón & Cano-Pasalodos presented within a Judith Curry blog-comment-thread. SIE records such as HadISST & Marsh et al (2016) developed from historical ice records show significantly higher SIE over the earlier pre-1950 years, perhaps 2M sq km higher. None of these show any AMO-like wobbles.
But what Connolly et al did manage to achieve was to present a graphic to the world (below) from Alekseev et al (2016) [paywalled] (but without the actual post-1979 SIE data plotted as in Alekseev et al (2015) Fig3b) and without mentioning the finding predicting of an ice-free Arctic summers by 2030.
If you are happy with the most basic of similarities being considered as being a "close correlation", the likes of this Alekseev et al (2016) graph may be assumed as an upside-down AMO graph but the assertion doesn't actually pass muster. Firstly the Alekseev et al graph is simply an upside-down version of a rather crude Arctic summer temperature record which are then no more than assumed as a proxy for Arctic summer SIE minimums. And even then, the upside-down AMO does have a very different shape. The 1950 AMO(us-d) was the same value as recent values with a peak inbetween in the 1970s (rather than 1960s) and a 'hiatus' since 1999. So AMO(us-d) is a long way off from being a proxy for Arctic SIE values.
MA Rodger @73 & prior,
thank you for the depth of knowledge which you add (to this and other threads) .
Being more than 48 hours, it is very likely that the commenter will not return to elaborate or dispute over his original comment.
( Each time there is a "drive-by" , I am yet again amazed at the chutzpah of a "drive-by-er" who chooses to raise his head above the parapet while possessing only a thumbnail of information/misinformation on the topic in question. How does a large bucketful of chutzpah manage to evaporate so quickly, before the making of a second comment? It seems the liquid chutzpah must be a highly volatile substance.
Eclectic @74,
This particular "drive-by-er" does have a history in the SkS comment threads. As far as I can see, he doesn't stick around to discuss points he raises but there is perhaps evidence of 'lurking' in this comment as it is replying to a previous in-thread comment.