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
Kevin@174
Why is it that you stop reading/processing information as soon as you see something that you think supports your predtermined conclusons?
The passage you quote talks about snowfall and melt. It does not talk about ice flow. Mass balance of a marine-terminating glacier depends on more than just snowfall and melt. Thre is not enough information in that quoted passage to support your conclusion that Antarctic Land Ice will increase.
Until you do a complete mass balance calculation, you will continue to arrive and unspported (and/or unsupportable) conclusions.
Sphaerica,
How do you read the quote from the AR4?
This is not cherry picked. This is AR4's summary of the TAR's prediction. It is not my interpretation. I copied the words directly.
How about the actual prediction from the TAR? Models predict.... Not Kevin interprets these models to predict. It says the models predict.
Explain how I am not understanding these predictions.
[JH] You seem to be more interested in playing "Gotcha" games with other commentors than engaging in a civil discussion of the science. As far as I am concerned, playing Gotcha is sloganeering which is banned by the SkS Comments Policy. Please cease and desist. If you do not, your posts will be summarily deleted.
Bob Loblaw,
How about the AR4's summary? The ice sheet is predicted to thicken!
I have shown IPCC's prediction that the ice sheet will thicken. Does someone have an IPCC prediction that the ice sheet will lessen?
[JH] You seem to be more interested in playing "Gotcha" games with other commentors than engaging in a civil discussion of the science. As far as I am concerned, playing Gotcha is sloganeering which is banned by the SkS Comments Policy. Please cease and desist. If you do not, your posts will be summarily deleted.
Kevin, the bottom line is that you're quoting FAR or TAR as a representative position. It's not. AR4 summarizes FAR but does not say, "And we still draw those conclusions." Discussing F/TAR might be interesting, but it's not relevant. AR4 is already being set aside. The science upon which AR5 rests is already in publication. Refer to it, as AR5 will. We now know more about the Antarctic. Get back into your time machine and return to the present.
Or don't, but don't be surprised if people ignore you, because F/TAR is just not that interesting.
DSL,
As I stated earlier, the latest prediction that the IPCC has made, predicts that Antartica will gain ice as temp increases.
The whole gist of this particular thread is that the ice will go down as temp increases, and that "Deniers" were incorrect in their belief that the increase in ice was contrary to predictions because it was only sea ice that increased, not Land ice.
I noted that there is a discrepancy in that the IPCC predicted an increase in Land ice, not a decrease. It very well could be that you are correct in that this thread was created after new research indicated that Land ice should decrease and not increase.
The AR4 did in fact come out prior to 2008, having come out in 2007 (with research obviously prior to that).
AR4 Ch 4.6.3.1 (2007): "Long-term data are very sparse, precluding confident identification of continent-wide trends."
Shepherd et al. (2013):
"We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth’s polar ice sheets. We find that there is good agreement between different satellite methods—especially in Greenland and West Antarctica—and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by –142 ± 49, +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes year−1, respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year−1 to the rate of global sea-level rise."
Antarctica, like Greenland, can show mass increase in the interior while still showing an overall net loss. That may be the source of some confusion.
Kevin - "...the latest prediction that the IPCC has made, predicts that Antartica will gain ice as temp increases."
That would be completely incorrect. From IPCC AR4, Chapter 4.6.2.2:
From the same document, FAQ 4.1:
[Emphasis in both quotes added]
---
You have been quote-mining old reports, not reading or incorporating the current science or observations, and clearly only looking at one side of the mass-balance equation while ignoring increased melting. I dislike saying this, but your last few posts have been nonsensical.
Everyone:
Please resist the temptation to "dogpile" on Kevin. Let his current conversation with DSL play out without interjecting comments.
KR excepted.
DSL,
I stated earlier that AR4 did not make a prediction, the prediction came from the TAR.
So, assume that AR4 is correct, and no trend is there. How does SkS come up with this thread then? Losing or gaining ice, sea or land, has no bearing, right?
[JH] You are now skating on the thin ice of sloganeering. Please cese and desist or face the consequences.
Kevin, where do the main articles rely on AR4? SkS is not a defense of AR4, nor would it matter in this case (see KR's response).
Kevin... "The ice sheet is predicted to thicken" ≠ Total ice mass balance will increase.
You're cherry picking and vastly oversimplifying.
DSL & Rob Honeycutt:
Kevin fell through the thin ice of slogannering and his most recent comment was deleted.
We know that Kevin has recused himself from participation, but lets take a quick review of insane denial, and clear things up along the way.
Kevin first quoted the 1990 IPCC First Accessment Report as claiming that Antarctica would experience increased snowfall. Kevin (1) quoted a 23 year old report and (2) proceeded to conflate increased snow fall with increased land ice. He also ignored the balance of the actual report, which very clearly lays out the details, as understood at that time, of Antarctic ice gain and loss. The tone of that report is nothing like Kevin's quote suggests.
When called on this, Kevin next quoted the 2007 IPPC Fourth Assessment Report -- but he chose to quote the FAR's review of the TAR —the Third Assessment Report, from 2001, 12 years ago. That section was a mere review of the previous report, in preparation for the more recent update. What's the point?
Somehow he skipped over the actual content of the FAR, which even more clearly than the first two reports discusses the ice gain and loss in Antarctica, including this:
Anyone can follow the link provided by KR to the actual page. People can judge for themselves what the IPCC has actually said about the subject, and how their understanding has progressed over time.
It is very, very important when faux-skepticism raises its ugly head to follow the quotes and the denial to the source, read everything with an open mind, and to understand what is truly there — not merely what some denier chooses to misrepresent.
Readers - There is actually a useful lesson in the last exchange(s) with Kevin. What he did was to selectively quote-mine old analyses (ignoring the last quarter-century of work), cherry-pick the data (East Antarctic while ignoring Antarctica as a whole), and misrepresent implications (wrongly equating increased snowfall with mass balance, ignoring greatly increased melt and calving). And concluding with a Bizzaro-world interpretation exactly opposite that of the IPCC.
This is in fact a fairly common denier tactic - select tiny bits of the science out of context and miscast them in contradiction to the whole. I strongly suggest reading the original sources (which isn't difficult if you start with abstracts and work your way up as you can or as desired), and check the quotes and sources.
IMO denial is broadcast with selective reading and presentation, some of which (see anything from Lord Monckton) is simply false. Armor yourself by checking the assertions from all participants.
I think it's a very good lesson in how "fake skepticism" works. You start with your preferred conclusion, find exceptions in the research that support than conclusion, then avoid attempting to understand the issue as a whole.
I have to admit, I see the attraction to doing this! It takes far less work to operate this way. Antarctica, in particular, is incredibly complicated (as if any aspect of climate change is simple). It's not easy to go through all the information and fully grasp what's going on. And it's especially hard when you clearly do not want to accept what scientists are saying.
How much time and energy does it take to quote mine, particularly when the targeted conclusion is going to be easily dismissed by readily available research? What a complete waste for Kevin, but what a nice, short example of the James Taylor School of Journalism for SkS.
Speaking of the complexity of Antarctica's climate...
Source: Antarctic ice tells conflicting story about climate change's role in big melt by Pete Spotts, The Christian Science Monitor, Apr 16, 2013
John Hartz - While not an SkS moderator, I might suggest that presenting 3-4 repeats of the same claims while disregarding other comments to be 'troll-like' behavior, and should probably be rewarded with the staged moderation warnings seen in other contexts here.
[DB] All parties: please return the discussion to the topic of this thread, Antarctica is gaining ice.
John, I have to question the logic of that Steig study reported in CSM. Basically, they looked at ice cores from the peninsula and high on the WAIS. The cores from the peninsula showed recent melting at a rate 10 times greater than the highest previous values while the cores from the WAIS showed melting at rates comparable to the highest previous values. From this they concluded that the peninsula is melting due to global warming and the WAIS due to natural variability.
The problem, as I see it, is that the majority of the WAIS ice loss is not occuring at the far inland locations where they gathered the ice cores. The WAIS (and the EAIS for that matter) are losing ice from the edges of the continent. Ice loss far inland may indeed be largely due to natural variability... but that is a tiny percentage of total ice loss. Much more is being lost at the edges of the ice sheet as warmer water (from global warming) causes ice shelves to break up and land ice calves into the oceans at a faster rate.
Essentially, the Steig study seems to be the equivalent of attempting to measure global warming by looking only at mid-day temperatures along the equator... the data which should show the least greenhouse warming signature. They failed to find a global warming signature in the WAIS ice loss because they only looked at the ice which is least likely to be impacted by global warming. If they had looked at ice loss around the edges of the ice sheet, where the vast majority of it is actually occurring, they should have gotten very different results.
Ok, so I am a noob here. but if I am reading this right there is increased loss of Land Ice in Antarctica and this fresh water freezes easier causing the sea ice to be greater? And even with the rise in temperature it is too small to cause the sea ice to melt. Is this basically the short version of the article?
I don't believe the ozone hole is the reason the south pole is getting colder. By saying this, we are basically saying that ozone is a more important greenhouse gas than CO2. If ozone is decreasing, in the presence of increasing CO2, the south pole should be getting warmer unless CO2 is less important than ozone as a greenhouse gas. But since the ozone is not currently decreasing, (it's been flat for years), this means we need to stop making this false claim. My null hypothesis is that ozone is NOT the reason the south pole is getting colder, for the reasons I gave. Disprove my null hypothesis, please.
What I mean is, since CO2 is much more important than ozone as a greenhouse gas, and CO2 is increasing, there is nothing O3 can do to make the south pole get colder. O3 can decrease, increase, stay the same, or drop to zero (it's close to zero anyway and has been for 30 years), there is no logical way we can deduct that O3 can make the south pole get colder. It is not logically possible, when CO2 is increasing. Impossible.
Morgan Wright @197 & 198, you appear to be missing several crucial facts in your discussion.
First, Antarctica is getting warmer, not colder. This has been shown in several recent studies, including by Steig et al (2009) and O'Donell et al (2010)
The rate of warming is low relative to much of the rest of the planet, an in particular the Arctic, but it is still warming. That has little bearing on the formation of sea ice, however, as during the Antarctic winter when sea ice forms, temperatures plummet so that it remains cold enough for sea ice to form even with the slight warming.
Second, it is not postulated above that ozone depletion encourages the formation of sea ice by cooling Antarctica, but rather by causing stronger winds, which push sea ice apart, exposing additional surface area in which sea ice can form. Reduced ozone does in fact cause cooling, but in the stratosphere, where the reduced ozone results in less UV radiation being absorbed, and hence less warming of the stratosphere. As it happens, increased CO2 reinforces this effect by radiating that heat which is captured away more effeciently. Therefore, at the relevant level of the atmosphere (the lower stratosphere) both reduced ozone and increased CO2 reinforce the same effect, ie, cooling the lower stratosphere.
The result of this colder air is that warmer air from the further north is drawn towards the low pressure system formed by the cooling of the air. This is particularly the case in the Southern Hemisphere summer, when the air north of Antarctica is particularly warm due to the Sun being more directly overhead. However, as the air is drawn towards Antarctica, it moves from a position of high rotational velocity to one of lower rotational velocity. Because angular momentum is conserved, this diverts the winds westward, forming a circumpolar vortex. The colder the Antarctic stratosphere, the further south the warm winds from further North penetrate, and hence the greater their angular velocity relative to the surface, ie, the faster the circumpolar vortex.
These faster winds then tend to break up the ice as explained above.
Third, the greenhouse effect over Antarctica is very weak, and sometimes negative. This may seem counterintuitive, but the greenhouse effect is a consequence of the difference in temperature between the source of IR radiation emitted at the ground, which is then absorbed by the atmosphere, and the temperature of the layer of the atmosphere which emits most IR radiation to space. In Antarctica, the surface is very cold. More importantly, most of the heat in Antarctica is brought by warm air from the north rather than from the direct radiation from the Sun. As a result, the air above Antarctica is very warm relative to the surface compared to, for example, the tropics. As a result, the greenhouse effect is very weak in Antarctica. Indeed, sometimes, and particularly in winter, the air above Antarctica will be warmer than the surface, resulting in a reverse greenhouse effect - ie, a cooling tendency from the greenhouse effect rather than a warming tendency. This can be seen in the figure below, showing IR radiation to space at various locations. You will notice in Antarctica there are humps at the same locations where in other areas their are dips. The humps indicate the atmosphere was warmer than the surface, and that at that time there was a reverse greenhouse effect.
Finally, a strengthened circumpolar vortex does in fact reduce the rate at which heat is transported into Antarctica. This does not cool Antarctica, for the strengthened vortex was created by an increased initial heatflow southwards. But it does significantly reduce the rate at which heat penetrates to the interior of Antarctica. This is plain in the heat map of Antarctica by O'Donell et al (2010) (above), where (I believe) the warming on the Antarctic Peninsula is much stronger than that in the rest of Antarctica. That is because it sticks out under the vortex (at least some of the time), and into the circumpolar currents driven by the vortex.
First, I did not say Antarctica is getting colder. I said the South Pole is. The chart you presented, of O'Donnell et al, clearly shows a large patch of blue over the south pole. Most other studies show the same thing. I understand the peninsula is warming and the pole is cooling. I am concerned about, and dispute, claims that the O3 hole is the reason for south polar cooling.
Second, you mention a low pressure system caused by the cooling of this air. This is never found. Cooling of air causes a high pressure system, always.
Third, you say CO2 increases cooling by radiating heat into the stratoshpere, and describe a reverse greenhouse effect over the pole. I appreciate that and find it interesting. I'm sure what you say is true because I've noticed the same thing flying over the arctic, where stratospheric temps outside the cabin were -40 F and the ground temp over northern Canada and Alaska were -60 or lower. Very interesting and probably more true of the antarctic. I see the hump in illustration (c) and vaguely remember that from college. Thank you.
Fourth, you say air north of Antarctica moves southward and the rotational velocity slows down because it conserves angular momentum. This is the opposite of how a vortex works. Air moving towards the center of a vortex always increases rotational speed as its radius from the center of the vortex decreases. Oh wait, at the end of the same paragraph you say the speed increases. Never mind. Maybe it was an error. However, a true vortex is caused by a low pressure zone and adjacent air moving into the low and rotating as it moves in due to conservation of angular momentum. In this case, the center of the vortex is a high pressure zone, the air is not moving in but moving west, and the rotation is caused by the rotation of the earth. It's not really a vortex at all. Compare this to how a hurricane works. Not even similar.
This conversation has been fun but says nothing about my original ozone skepticism.