Arguments
Is Antarctica losing or gaining ice?
What the science says...
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Antarctic sea ice extent has expanded at times but is currently (2023) low. In contrast, Antarctica is losing land ice at an accelerating rate and that has serious implications for sea level rise. |
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Climate Myth...
Antarctica is gaining ice
"[Ice] is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap." (Greg Roberts, The Australian)
At a glance
Who discovered the great, South Pole-straddling continent of Antarctica? According to the National Geographic, Captain Cook came within an estimated 80 miles of it in the late 1700s, but the three first 'official' discoveries all took place in 1820 by Russian, British and American teams of seafarers respectively.
Since that initial discovery, Antarctica has attracted and inspired researchers and explorers alike. It's a challenging place, fringed by sea-ice that, unlike the Arctic, has not steadily declined but whose extent fluctuates on a seasonal basis: it's currently (February 2023) at a very low coverage, but it can and does recover from such dips. Antarctic sea-ice is no great problem, with the exception of albedo-loss in low extent years: if it all melted, it would have no effect on global sea-levels. It's the stuff on land we need to focus upon.
The land of Antarctica is a continent in two parts, divided by the 2,000 m high Transantarctic Mountains. The two parts differ in so many respects that they need to be considered separately. East Antarctica, that includes the South Pole, has the far greater landmass out of the two, some 4,000 by 2,500 kilometres in size. Although its massive ice-sheet, mostly grounded above sea level, would cause 52 metres of sea level rise if it completely melted, so far it has remained relatively stable. Snow accumulation seems to be keeping in step with any peripheral melting.
In contrast, in the absence of ice, West Antarctica would consist of islands of various sizes plus the West Antarctic Peninsula, a long mountainous arm pointing northwards towards the tip of South America. The ice sheet overlying this mixed topography is therefore grounded below sea level in many places and that's what makes it far more prone to melting as the oceans warm up. Currently, the ice-sheet is buttressed by the huge ice-shelves that surround it, extending out to sea. These slow down the glaciers that drain the ice-sheet seawards.
The risk in West Antarctica is that these shelves will break up and then there will be nothing to hold back those glaciers. This has already happened along the West Antarctic Peninsula: in 1998-2002 much of the Larsen B ice-shelf collapsed. On Western Antarctica's west coast, the ice-sheet buttressing the Thwaites Glacier – a huge body of ice with a similar surface area to the UK - is a major cause for concern. The glacier, grounded 1,000 metres below sea level, is retreating quickly. If it all melted, that would raise global sea levels by 65 centimetres.
Such processes are happening right now and may not be stoppable - they certainly will not be if our CO2 emissions continue apace. But there’s another number to consider: 615 ppm. That is the CO2 level beneath which East Antarctica’s main ice sheet behaves in a mostly stable fashion. Go above that figure and the opposite occurs - major instability. And through our emissions, we’ve gone more than a third of the way there (320 to 420 ppm) since 1965. If we don’t curb those emissions, we’ll cross that line in well under a century.
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
Arguments that we needn't worry about loss of ice in the Antarctic because sea ice is growing or even that sea ice in the Antarctic disproves that global warming is a real concern hinge on confusion about differences between sea and land ice, and what our best information about Antarctic ice tells us.
As well, the trend in Antarctic sea ice is not a permanent feature, as we'll see. But let's look at the main issues first.
- Sea ice doesn't play a role in sea level rise or fall.
- Melting land ice contributes to sea level rise.
- The net, total behavior of all ice in the Antarctic is causing a significant and accelerating rise in sea level.
Antarctic sea ice is ice which forms in salt water mostly during winter months. When sea ice melts, sea level does not change.
Antarctic land ice is the ice which has accumulated over thousands of years in Antarctica by snowfall. This land ice is stored ocean water that once fell as precipitation. When this ice melts, the resulting water returns to the ocean, raising sea level.
What's up with Antarctic sea ice?
At both poles, sea ice grows and shrinks on an annual basis. While the maximum amount of cover varies from year to year, there is no effect on sea level due to this cyclic process.
Figure 1: Coverage of sea ice in both the Arctic (Top) and Antarctica (Bottom) for both summer minimums and winter maximums. Source: National Snow and Ice Data Center
Trends in Antarctic sea ice are easily deceptive. For many years, Antarctic sea was increasing overall, but that shows signs of changing as ice extent has sharply declined more recently. Meanwhile, what's the relationship of sea ice to our activities? Ironically, plausible reasons for change may be of our own making:
- Ozone levels over Antarctica have dropped causing stratospheric cooling and increasing winds which lead to more areas of open water that can be frozen (Gillett & Thompson 2003, Thompson & Solomon 2002, Turner et al. 2009).
- The Southern Ocean is freshening because of increased rain and snowfall as well as an increase in meltwater coming from the edges of Antarctica's land ice (Zhang 2007, Bintanja et al. 2013). Together, these change the composition of the different layers in the ocean there causing less mixing between warm and cold layers and thus less melted sea and coastal land ice.
Against those factors, we continue to search for final answers to why certain areas of Antarctic sea ice grew over the past few decades (Turner et al. 2015).
More lately, sea ice in southern latitudes has shown a precipitous year-on-year decline (Parkinson 2019). While there's a remaining net increase in annual high point sea ice, the total increase has been sharply reduced and continues to decline.
How is Antarctic land ice doing?
We've seen that Antarctic sea ice is irrelevant to the main problem we're facing with overall loss of ice in the Antarctic: rising sea level. That leaves land ice to consider.
Figure 2: Total Antarctic land ice changes and approximate sea level contributions using a combination of different measurement techniques (IMBIE, 2017). Shaded areas represent measurement uncertainty.
Estimates of recent changes in Antarctic land ice (Figure 2) show an increasing contribution to sea level. Between 1992 and 2017, the Antarctic Ice Sheets overall lost 2,720 giga-tonnes (Gt) or 2,720,000,000,000 tonnes into the oceans, at an average rate of 108 Gt per year (Gt/yr). Because a reduction in mass of 360 Gt/year represents an annual global-average sea level rise of 1 mm, these estimates equate to an increase in global-average sea levels by 0.3 mm/yr.
There is variation between regions within Antarctica as can be seen in Figure 2. The West Antarctic Ice Sheet and the Antarctic Peninsula Ice Sheet are losing a lot of ice mass, at an overall increasing rate. The East Antarctic Ice Sheet has grown slightly over the period shown. The net result is a massive loss of ice. However, under a high-emissions scenario, ice-loss from the East Antarctic ice-sheet is expected to be a much greater in the decades after 2100, as reported recently by Stokes et al. (2022). That’s a scenario we must avoid at all costs.
Takeaway
Independent data from multiple measurement techniques (explained here) show the same thing: Antarctica is losing land ice as a whole and these losses are accelerating. Meanwhile, Antarctic sea ice is irrelevant to what's important about Antarctic ice in general.
Last updated on 14 February 2023 by John Mason. View Archives
Karly wrote "An interesting example of how science is not done."
well quite, science is done by publishing papers in peer reviewed scientific journals and it is not done by gratuitously insulting those who disagree with you ("If I had but the time and you had but the brain—").
FWIW I have a first class degree and a PhD, and I have published a fair few journal papers, including a couple on climate. However that is irrelevant as in science it is the validity of the argument that matters, not its source. Perhaps you should pay a bit more attention to the scientific argument rather than engaging in inaccurate ad-hominems.
Oh, for heaven's sake. Validity is not measured by peer review...many, many peer reviewed papers have been shown to be erroneous as knowledge has progressed. Duncan Steel has calculated a change in spring insolation over time. Either his calculations, using accepted orbital mechanics and physics are correct or not. No-one has yet shown they are incorrect. What the effect of that change in insolation is may well be arguable, but it's the change that's significant, and unless you can show the calculations (of the change in insolation) are incorrect you have little to add to the discussion of his 'essay'
kiwiradical Validity is indeed not measured by peer review and many peer-reviewed papers have indeed been shown to be wrong. However, the proportion of peer-reviewed papers that are wrong is rather less than the proportion of ideas on non-peer reviewed websites where people publish their ideas without submitting them to external scrutiny first. That is why scientists use peer-review.
The key thing here is that Duncan Steel has responded to criticisms of his work with gratuitous insults. That is not the way science ought to procede.
kiwiradical @352, granting that Steel is entirely correct about all that he claims with regard to changes in insolation only, his theory that it is a significant effect does not follow. The reason it does not follow is that absent data on albedo, the the changes in insolation average out to near zero over the globe and over the year. They are inconsequential. Steel knows that, so he makes some attempt to indicate potential albedo changes that might make the effect significant. I have criticized those attempts @342 above, something you have ignored. Specifically, my criticisms were that:
1) The change in albedo he assumes is not justified by the magnitude of the effect, in that he conjectures that a 4.33 day drift in perihelion relative to the vernal equinox results in a 30 day drift in ice and snow melt;
2) The change in albedo he proposes is contradicted by emperical evidence of recent changes in snow and ice; and
3) He incorrectly includes feedbacks from AGW, from other natural warming, and from the drift of the perihelion in calculating the forcing of the the effect.
Since then I have done some analysis that may help give some idea of the impact of the third point. Specifically, I have used Steel's image of latitudinal absorptivity by day of year to determine the absorptivity by day of year. I have then plotted that against both the introduced drift in seasonal ice and snow cover that he appeals to, and the current insolation by day at that latitude:
The units are standard deviation units. To determine the change in the energy balance, you would actually need to take the integral of the produces of the absorptivity and the insolation, in original units. It is far simpler, however, to compare them in StDev units so that you can compare the position of the peaks.
Many people don't realize that the peak in insolation substantially precedes the peak in ice and snow melt, a fact that can be seen by comparing the blue and orange curves above. The failure of the peaks to coincide significantly reduces the total energy input from the sun in high latitudes.
That being the case, the effect of delaying the ice melt by another thirty days (Steel's model for the albedo 250 years ago) will by itself, without any change in insolation, greatly reduce the energy absorbed at high latitudes. It does so by pushing the albedo and energy peaks further out of phase (blue and yellow curves).
It is evident from this diagram, and without need of calculation that Steel's albedo model will introduce a large "forcing" all by itself, and without any change in insolation. What is worse, however, is that the insolation change is a mere 4.33 day drift in insolation, just 14.4% of the albedo drift. There is slightly more to it than that, but that is the most important effect. That effect can be approximated by blue line four days the right, to represent the insolation change. (Let me emphasize that that is not exact, but it is close enough for estimating the effect.)
The forcing from the insolation change can then be determined as the change in the integrated products of the orange line and the blue line relative to the orange line and the blue line shifted four days to the right. The effects of the feedbacks from all forcings combined (assuming Steel's albedo model is correct) is then the difference between the integrated product of the blue and the orange lines, and the blue and the yellow lines. Transparently, that will be of the order of 15% of the feedbacks. In other words, only about 13% of Steel's calculated "forcing" is an actual forcing effect of the change in insolation.
That is a large error on Steel's behalf (far larger in effect than any he is attributing to the climate scientists). It is somewhat mute because of the clear errors in his albedo model; but the flaw in method revealed would have exagerated the absolute value of the apparent impact of the effect no matter what albedo model was used.
Put simply, he is counting feedbacks as part of the forcing - and not just feedbacks from the forcing under consideration, but feedbacks from any forcing, including some which are far stronger and hence far more dominant than those he has found.
While on the topic of his albedo model, I noticed today a nuance that I had previously ignored. Specifically, he describes the model, saying:
Note that northern latitudes from March to June is when the change in insolation is strongly positive. He has deliberately excluded changes in albedo for periods when the change in insolation has been negative, thereby exagerating the effect still further. (Note that the time restriction on the adjustment means he assumes snow and ice will freeze at the same time 250 years ago as they do currently, not later as I have stated elsewhere. That assumption is still falfified by the fact that they are freezing later. It also means the graph above is not representative of his model in that it applies the adjustement to the entire year. The adjustment applied as he states, however, would introduce discontinuities into the graph, which would consequently be underspecified. Therefore, until he sees fit to fully specifiy the model, it stands as a reasonable approximation.)
kiwiradical @352.
You say "Either his calculations, using accepted orbital mechanics and physics are correct or not." You ignore the possibility that the subject of the calculations of duncansteel are already being accounted for. And also that the effect may or may not be significant.
duncansteel is actually presenting two effects although he doesn't make this at all clear.
In his published paper he calls one CIT. This is undisputedly already taken onboard by climatology (although to read his paper you wouldn't think so). And note that the effect of this orbital change is small in comparison with solar variation which is itself small in comparison with AGW. So in the grand scheme of things it is insignificant.
A second orbital effect duncansteel calls CSI in his 'essay'. This is smaller again than CIT and duncansteel has identified its absence from a set of NOAA insolation tables. (These tables provide insolation data for the last 10 million years in 1,000 year steps.) It is probably no great loss from such tables as the impact of CSI is much smaller than even CIT. There is remaining doubt as to whether or not this CSI is accounted for already or whether it is something so far overlooked. Sadly it is duncansteel who should be the arbitor of his rather poorly described theorising, a role he appears poorly matched to, while the poor description makes it inconvenient for other to take on that role for him. Add in his crazy climatological inferences (as per @354) and all sympathy for duncansteel quickly discipates.
The tenor of duncansteel in this matter can perhaps be judged by where he has come from on this matter. He talls us he was inspired to the research that led to his 'CSI/CIT trumps AGW' hypothesis by Thomson (1995) 'The Seasons, Global Temperature and prescession'. Thomson may be beating the drum for orbital effects to be accounted for better in AGW calculations but Thomson's two concluding paragraphs show clearly that duncansteel is way off on his own concerning the implications of such effects w.r.t AGW.
@351
Good on you. I have an Honours BSc, a PhD, an MSc, and a DSc. I have also published over 150 peer reviewed journal articles. Did you think you were going to intimidate me?
Given Dikran opened his remarks on qualifications with 'FWIW' and then described his own qualifications as irrelevant to the science, I don't see an attempt at intimidation. I consider it a response to your statement:
To me it looks like you have invited posters to lay out their expertise, only to accuse them of intimidation when they do.
Can we actually have the qualifications of the commentators?
Dr Steel is a world expert on astrophysics. It seems only fair that tthose criticising him should acknowledge their own expertise.
If they are reluctant, then I think it is reasonable to discard their opinions as complete rubbish.
[Rob P] - Presumably you'd be happy with a proctologist performing open heart surgery on you?
Actual experts on any given subject are those that have their ideas published in the scientific literature and their research subjected to scrutiny by their peers. Convincing ones peers of the validity of your research in a given scientific discipline is a good measure of expertise. Does Dr Steel have any publications relevant to the subject under discussion? Is there any indication of support for his ideas in the relevant scientific community?
Karly,
Dr Steel has the option of returning to defend his ideas in this forum, submitting his ideas to peer review, or leaving us with the impression that he is not to be taken seriously. So far, your efforts on his behalf have not really changed those options or improved that impression, but it is not to late to offer something useful. If you have specific comments to make on the content of his theories, rather than impressionistic views of the various personalities involved in this discussion, please share them.
Karly, everyone possesses a set of naive algorithms for establishing the veracity of arguments that are beyond their comprehension.
If you acknowledge that the contention between Steel and Curtis/Rodger is in fact, beyond your comprehension you will need to resort to your truthiness algorithm.
The thing is, people don't necessarily want to engage in the requisite PhDenis measuring competition that you propose. Opinions have been provided, which the informed reader can use, along with the behaviour of the parties involved, to come to a conclusion.
karly @358:
I take this to be an admission by karly that neither they, nor Dr Steel, are able to defend his numerous blunders on climate science, nor his completely falsified model of albedo changes; and that therefore they need to shift the grounds of debate to argument from illegitimate authority. (Illegitimate because Dr Steel has no qualifications on climate science; and illegitimate because karly is "... not a physicist, astronomer or climate scientist".)
Of course, having previously declared their incompetence to assess the empirical evidence and the cogency of arguments offered, it is a bit difficult now for karly to claim to be able to assess the arguments on their merits.
"I have read [karly's contribution down] this thread with sheer astonishment." For someone to proclaim "I have an Honours BSc, a PhD, an MSc, and a DSc." Full stop. That is strange enough to raise questions as to why it would be said truthfully.
And for that same person to also state that which is now erased by the moderators, that raises little doubt as to the answer to that question.
Karly, even though I don't hold a DSc., trust me when I tell you that holders of multiple degrees almost always act with a certain humility (although that doesn't stop them behaving with extreme 'robustness' when the occasion calls for it, and may times when it isn't). It is not at all necessary for clever people to tell the world that they are clever. Their abilities speaks for themselves.
And why is it necessary to know the qualifications of a commenter? Why would you say "If they are reluctant, then I think it is reasonable to discard their opinions as complete rubbish"? Somebody capable of post-graduate qualification should be able to judge the veracity of a commenter here by what they say alone. Or if not, the comment can be checked by a little research on this wonderful interweb the world is now blessed with. I thus would suggest to you that this thought @358, as you relate it to us, it is actually very "unreasonable."
karly wrote "Good on you. I have an Honours BSc, a PhD, an MSc, and a DSc. I have also published over 150 peer reviewed journal articles. Did you think you were going to intimidate me?"
No, it was you that questioned the qualifications of those posting criticisms of Dr Steel's work here, I was merey indulging your curiosity. I also made it clear that qualifications mean nothing in scientific discussions, what matters is whether the argument is correct. That would be an odd thing to write if I was trying to intimidate somebody. My reason for mentioning this was to point out that questioning qualifications is an ad-hominem attack.
". It seems only fair that tthose criticising him should acknowledge their own expertise."
why should anybody do that, given that your response to me indulging your curiosity on this point was a personal attack?
I note that karly is trying very hard to avoid discussing the actual content of Dr Steel's argument, which seems pretty odd for an academic such high apparent calibre.
"If they are reluctant, then I think it is reasonable to discard their opinions as complete rubbish."
That is the most stupid thing I have read in a while. (-snip-) It amounts to a blanket argument from authority. Not to mention we're not talking about opinions but specific criticisms that can be adressed in methodical fashion. It is hard to understand how someone with as much alphabet soup as Karly claims can have such a lapse in rational thinking. The argument can obviously be turned on its head to say that, if Dr Steel has no training in atmospheric sciences whatsoever, his opinion on climate should be dismissed as complete rubbish.
Now, how about discussing that albedo problem?
[RH] Let's check the tone here.
"Dr Steel is a world expert on astrophysics."
But that doesn't make him an expert on climate. Changes in insolation and their radiative effects on climate are understood by climate scientists. It's well understood as a very slow and minor forcing, whereas we are witnessing a large and rapid change in climate today that is consistent with the large radiative forcing of man-made greenhouse gases.
Expert or not, Dr. Steele's credentials _do not automatically make him correct _. That is the basis of the fallacy of arguing from authority.
As has been pointed out on this thread, Steele has made some rather elementary and invalidating errors. Science stands or falls based on content, on whether or not it fits the evidence. Steele's hypothesis fails that test.
I know someone in the comments section must've already brought it up, but I don't really want to fish through eight pages. Can anybody tell me what's the deal with the papers from Frezzotti et al and Zwally saying that in fact the Antarctic is actually gaining ice overall over the last 800 years?
Antarctica gaining Ice Mass (balance*) — and is not extraordinary compared to 800 years of data
[JH] For future reference, the SkS search engine is a useful tool.
@dvaytw 367:
For a detailed discussion of Zwally et al (2005) and similar papers, see Robert Way's article, New and Improved Ice Loss Estimates for Polar Ice Sheets posted on Oct 1. 2014.
dvaytw - Long story short, that title is based on a misunderstanding. Frezzotti et al 2013 is discussing the surface mass balance, which is the amount of incoming mass in Antarctica, comparing ice cores to models for that quantity. This is an input quantity only.
They are not looking at the total mass balance, the total change of ice mass due to the balance of input (snow) and output (melt, glacier calving), which show Antarctic mass loss.
I suspect the emphasis of that 'skeptic' title is due to a misunderstanding of that point.
Just thought that I would note that there is very nice review article on Antarctic sea ice increase and theories about why this happening by Eric Steig here. In short, it is the winds, but it is also rather complicated. Also, the transient response (what we see here) is likely different from the equilibrium response. It also points an interesting paper by here where a model driven by all the observed changes in winds pretty much reproduces the pattern in sea ice seen. h/t to Realclimate but thought this was an interesting addition to this thread.
I am not a scientist, merely a layman that discusses politics and current events with my 20 year old son studying engineering, physics and math at the University of Waterloo in Canada. He supports the claim that climate is changing and the polar ice cap is shrinking. I am a right wing skeptic so I am searching for more info on this claim. Our only right wing media (Sun News) regularly scrutinizes these and other topics with in depth reports and documetaries. I find them extremely interesting and much more balanced than what I see on main stream media, (hence my skepticism). I found this article from "mail online", also called "Daily Mail" and was hoping this forum could do a "peer review" of sorts on it. (I'm sorry to have copied & pasted the entire document but I knew no other way to share it here).
Read more: http://www.dailymail.co.uk/sciencetech/article-2738653/Stunning-satellite-images-summer-ice-cap-thicker-covers-1-7million-square-kilometres-MORE-2-years-ago-despite-Al-Gore-s-prediction-ICE-FREE-now.html#ixzz3MSUzouTW
[Rob P] Please don't copy/paste screeds of text. I have removed it but, in the future, a simple link will suffice. Also, note the correct threads for this are the Arctic sea ice and polar bear myths - as Composer99 points out.
alan2112drums:
I believe you can simply share the link (which you did at the bottom of your post - unless that's for a related post) and either paste/quote relevant highlights or paraphrase what you think are the key points, rather than copy/pasting the entire article - especially since the Daily Mail still has copyright on its own content.
Please note that this original post & thread are meant to discuss the behaviour of Antarctic ice, and as such remarks about either the Arctic sea ice or polar bear populations - which appear to be the main poitns of contention raised by the Daily Mail article - are off-topic.
Threads for further follow-up (including responses):
alan2112drums:
I have responded here to the point raised by the Daily Mail about sea ice. Perhaps others will offer additional perspectives.
I must leave it to others to address the polar bear matter - although the on-topic post I have shared does, too.
(I have to get to cleaning a bathroom. Fun times.)
I have placed some updated information on Polar Bears here.
I have replied to that nonsense about Al Gore and Arctic Sea Ice demise by such-and-such date, here.