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
Tuerqas @223, here is a USGS map of the major fault lines around the world:
The key thing to note is that there are no fault lines within the Antarctic plate, and hence no fault lines within Antarctica. Therefore East Antarctica and West Antarctica are not moving away from each other at all, let alone at an increasing rate. They are not even on different tectonic plates. That is why there are very few earthquakes in Antarctica (see also),and limited volcanic activity.
There are some minor faults within the Antarctic plate, but I can find no evidence of rifting or mountain building in Antarctica more recently than 65 to 100 million years ago. Given that, absent peer reviewed evidence to the contrary, it appears you have simply made up (or swallowed somebodies line) about increased vulcanism in Antarctica.
One at a time, DSL: Non-theoretic studies are relatively sparse on many
topics concerning Antarctica. What I can do is point out that if you look up a list of volcanoes in Antarctica with eruption history, there were 9 with listed dates or approximate guesses of dates going back to 5550 BC. Four of the have been in the last 50 years. That seems like pretty significant evidence to me that there is increased activity.
scaddenp: Roger Highfield an AGW proponent wrote an article in Feb 2006 about how Krakatoa is still cooling the earth today. I said decades. An expert who fully believes in AGW said a century. What is your evidence for 'a couple of years'? I agree there have been no eruptions of this type in the Antarctic region, yet there have been at the very least 4 in the last 50 years that have not spewed tons of debris in to the stratosphere. Is the heat, contained under ice, insignificant? As DSL obliquely points out, there is little interest in doing studies in Antarctica that minimize AGW, so we don't know. I do know that geothermal heat activity has kept a place like Iceland free of ice and livable since long before the industrial age. it shows to me that volcanic heat is capable of affecting glaciers on a significant scale.
Tom Curtis: I could find no maps that show the plates from either of the pole sides so you may be 100% correct. It is evident in your picture above that the Antarctic plate splits nearly in half as it approaches the Scotia plate. I could not find a map that shows both this plate picture and the placement of the Seal Nunatak volcanic range. I did read that the range splits the Antarctic plate and that it was on plate fault line, but it was from a skeptic author so I won't bother pushing it.
<Snip> (removed accusations of fraud and inflammatory political comment)
[PS] Please read the comments policy. Compliance is not optional. Note particularly political rants and accusations of fraud etc. This is a site for discussing the science. There are other places which welcome commentary of this type.
Tuerqas, you wrote @ 227: "I could find no maps that show the plates..."
So what did you base your contention @ 223 on that: "... geological studies clearly show that the tectonic plates between the eastern and western antarctic ice sheets have been moving (away from each other causing volcanic emission) at an increasing rate."
Roger D, please read more carefully. I could find no maps with a polar oriented view. Need I explain to you that a flat map makes the north and south pole areas look bigger than they really are? The only tectonic plate map I could find was the same one Tom Curtis linked and if it were accurate, the Antarctic plate is larger than the Pacific plate. Are you maintaining that the map above is accurate in size and that the Antarctic plate is actually larger than the pacific plate? If you are, I know how seriously to take you. If you now understand my point and can provide a tectonic plate picture as seen with the south pole at the center so that the Antarctic plate is not vastly distorted, it would be greatly appreciated.
To the editor, I understand that ad hominem attacks will be deleted and am delighted. How about blatant misrepresentations, like taking part of a commentary quote out of context for badly scored 'gotcha' attempts? Are they deleted?
[RH] Roger has asked you to substantiate the fundamental position you've put forth. That's hardly a "gotcha." Everyone who comments at SkS, regardless of their position on AGW, is expected to be able to cite sources for their claims.
Edit: Just to clarify. When you state something as clear as "geological studies clearly show" that should be accompanied by references to the actual geological studies (plural in this case) that are clearly showing what you are saying.
Tuerqas:
"Non-theoretic studies are relatively sparse on many topics concerning Antarctica."
No kidding?
"What I can do is point out that if you look up a list of volcanoes in Antarctica with eruption history, there were 9 with listed dates or approximate guesses of dates going back to 5550 BC. Four of the have been in the last 50 years. That seems like pretty significant evidence to me that there is increased activity."
Does it? And you say nothing about the increased observation of Antarctica in the last fifty years? But that's not really what we're talking about here. We're talking about generally increased volcanic activity that would result in the kind of general net decline in Antarctic land ice. Am I correct in assuming you've picked up the meme going around concerning Antarctic geothermal flux in the Thwaites region.
Can I get an acknowledgment that this part of your original claim is baseless: "one can even get an admission that volcanic activity has been steadily increasing in the antarctic."
Tuerqas @227, in no particular order:
1)
In fact Iceland is one of the few areas at its latitude to have icecaps, which are largely absent at that latitude in Eurasia, and found futher north in Canada. Greenland has ice sheets further south, and hence represents the unusual case. Further, there is no correlation between volcanism in Iceland and the lack of ice caps:
This does not mean that geothermal activity is not a factor in keeping parts of Iceland ice free. However, it is not the major factor, even in Iceland.
2)
Comparing with Iceland again, since 900 AD there have been more than 205 eruptions in Iceland. More than, because 13 of the "eruptive events" have been "fires", the most recent of which (Kraffla 1975-84) contained 9 distinct erruptions. Over that period there has been an "...An apparent stepwise increase in eruption frequency is observed over the last 1100 years...", but that merely "... reflects improved documentation of eruptive events with time". Given that exploration of Antarctica has been exlusively restricted to the last 150 years, with significant observations restricted to the establishment of Antarctic bases in 1958 and later, an increased observation of erruptions in the 20th century proves no more than an increased frequency of observation in the 20th century.
3)
That is not obvious to me at all. What is obvious is that the map only shows some of the coastal regions of Antarctica and so gives no true indication of its width. This map will give you some indication, with the Scotia Plate lying just north east of the Antarctic Peninsula (60 degrees West):
4)
The Seal Nunataks are near the Larsen Ice Shelf on the Antarctic Peninsula, and hence most certainly do not split Antarctica. Indeed, as can be seen from the map above, observed volcanism in Antarctica is largely restricted to a coastal band south of the Pacific Ocean.
Tuerquas - Yes you are correct about volcanic influence lasting more than decade. You did not provide a link but I assume you refer to an article where Highfield (a science editor) reports on a paper by Gleick et al. While the aerosol influence last less than a decade, the influence on surface temperatures continues because of the slow mixing of cooled waters on the ocean surface.
However, as to effect in the antarctic, a better representation of volcanic record is from ice core. Ie from this paper. Interesting the major impacts on Antarctic ice have been mostly from tropical volcanoes rather than local ones which does not support your thesis.
Tuerqas @229.
Are you having a laugh? How many maps with a southern projection do you need?
And you ask "Are you maintaining that the map above is accurate in size and that the Antarctic plate is actually larger than the pacific plate?" Are you entirely unfamiliar with the Mercator Projection?
Indeed, do you find Wikipedia difficult to cope with? It is hardily an obscure source and it says of the Antarctic tectonic plate "The Antarctic plate is roughly 60,900,000 square kilometers. It is the fifth biggest plate in the world." and of the Pacific Plate "At 103 million square kilometres, it is the largest tectonic plate."
<Snip> Inflammatory tone
[PS] Can everyone please cool it and stick to the science.
Shepherd et al. (2012) estimate the mass balance of the entire Antarctic Ice Sheet to be -81 ± 37 gigatonnes per year. The tolerance band is less than Lake Superior's 2014 ice volume change when 2 feet thick ice formed over the 32 thousand square mile lake. Canada has over 320 thousand square miles of lakes that get ice each winter. Antarctica's 81 GT loss per year may not be much when compared to the millions of GT there.
Are you serious? Let's suppose say that Canada's lakes gain and lose say 1000Gt of ice between summer and winter. Only a change in the surface area of lakes frozen or a change in timing (which would both affect earth albedo) would have any climate significance. On the other hand, 81Gt of ice loss from Antarctica is going straight into sealevel rise. Furthermore, as rock is exposed albedo is reduced.
jetfuel, setting aside the different effects of ice in different locations outlined by scaddenp... you are also comparing the antarctic annual volume loss rate to (vague generalizations of) the Canadian annual volume maximum. That is obviously illogical.
That 81 GT average was over the period 1992 - 2011... twenty years. So the total ice loss for that period was ~1,620 GT. Meanwhile, the total annual ice gain in Canadian lakes over the same period was, what? Approximately zero? In Summer they are melted out so we've gone from zero ice volume to zero ice volume. In winter they freeze to varying extents, but setting aside the one anomalous year you cite, the overall trend has likely been decreasing ice volume. In any case, any changes in average volume over the course of the year have been minimal compared to the Antarctic ice loss.
jetfuel is IMO grasping at straws, and has been for some time.
Although that's really all that needs be said, I should add that jetfuel is trying to compare cumulative year-over-year land ice mass loss in Antarctica with (cyclical) seasonal river/lake ice volume gain in Canada - and ignoring the inevitable melt-away of the latter.
At best, maybe jetfuel would be on to something if the change in seasonal ice/snow cover in Canada is measurably altering the albedo, as scaddenp notes, but I doubt we'll see jetfuel come up with any evidence showing the existence or magnitude of such an effect.
The twenty year cumulative 1620 GT loss of Antarctic Land Ice, when compared to the 26450000 GT on Antarctica is .00006 or .000003 per year on avg. as a fraction. Since 97% of all water is ocean water, and Antarctica holds 61% of all fresh water, all those 20 years of melt together have dilluted the oceans by .0000010 as a fractional addition of fresh to salt water. What evidence is there that that tiny fractional change alters the temp at which the ocean salt water freezes or makes any discernable change to the behavior of the oceans? How could a large percent of the 81 Gt of net melt per year exposing rock? The ice is 8200 feet thick even on the penninsula. As far as am I serious, I was comparing to the seasonal N.A. lake ice because 81 out of 26.45 million gigatonnes isn't an appreciative amount of loss. If a larger amount of temporary lake ice gain is unimportant, how is that amount (81 GT) of loss important?
[JH] Please document the sources of the data that you have used in the above post.
You have a history of posting comments like the above without providing any citations. You have been repeatedly asked to provide documentation. For the most part, you have ignored these requests. If you continue this pattern of behavior, you will relinquish your privalege of posting on this website.
jetfuel: "What evidence is there that that tiny fractional change alters the temp at which the ocean salt water freezes or makes any discernable change to the behavior of the oceans?"
Are you assuming that Antarctic runoff is instantly dispersed throught the world's ocean volume?
Jetfuel: "If a larger amount of temporary lake ice gain is unimportant, how is that amount (81 GT) of loss important?"
This is almost identical to the "temp changes by 15-20C over the course of year in some places; therefore, getting worked up over 0.7C in fifty years is ridiculous" argument. The thing is, Antarctic land ice loss will continue and accelerate as glacial terminators erode more and more quickly. Antarctic land ice won't reach equilibrium with global climate for hundreds if not thousands of years.
DSL .... is global warming and the related CO2 rise causing Antarctica to lose its land ice?
[TD] Donny, you need to read the original post before commenting on this thread, so you don't waste space and everyone's time asking questions that already are answered. If you then want to ask specific questions about, or object to (with data to back you up), contentions made in the original post, please do go ahead.
And make sure you read the intermediate tab, Donny. You might also want to look at the literature on the subject.
I have. Wanted to hear your educated opinion.
The problem I have with the original post (yes intermediate) is what study was used to make the leap that despite sea ice gains the thermal energy of the warming oceans make its way through the ice (which is an insulator) and causing land ice loss. Land ice loss seems more likely to come from geothermal dynamics. The authors original post would make more sense if all land ice loss was relegated to the coast. ... not sure from my readings if that is the case.
I also wonder if the antarctic ocean waters cool more in the summer because of a lack of sea ice. There may be too much thermal mass (as well as other variables) involved to see seasonal trends.
"What evidence is there that that tiny fractional change alters the temp at which the ocean salt water freezes or makes any discernable change to the behavior of the oceans?"
DSL:"Are you assuming that Antarctic runoff is instantly dispersed throught the world's ocean volume?"
Remember when the Malaysian airline went down in the Indian Ocean west of Australia? Remember how the surface wreckage was expected to have moved by 150 miles per day? It's called currents. .00006 over 20 years isn't much of a fraction of fresh water addition to water moving many miles per day. Most AGW arguments are based on substantial dispersion of one substance into another. When the dispersion doesn't support your ideas, sorry, you can't make it stop. Unusually high Antarctic sea ice is surrounding most of the continent across thousands of miles of sea ice perimeter. My question remains.
And not to pile on .... but why is the increased atmospheric moisture level going to result in increased perception in the desert of Antarctica?
Jetfuel. ... it probably freezes before it can disperse.
DSL: "The thing is, Antarctic land ice loss will continue and accelerate as glacial terminators erode more and more quickly. Antarctic land ice won't reach equilibrium with global climate for hundreds if not thousands of years."
The quick increase of a miniscule rate is not of any consequence. Eventually people will be educated that 81 GT to 24.5M GT is like a couple droplets to an avg size swimming pool.
But wait. ... if most of the melting comes in the summer (which I would assume but don't know for sure) then yes the water would have time to disperse before the ice started to form again.