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
OK on second read where you say the air moves from a position of high rotational velocity to low velocity, you were talking about the velocity of the rotating earth, not the rotational velocity of the air. OK never mind. As long as we are on the same page.
Now, what about the ozone? Or lack thereof.
Morgan Wright @200 & 202:
1) The South Pole itself is not in the blue patch shown on the O'Donell et al map, but rather on the border. The temperature trend at the South Pole as measured by instruments on the surface is scarcely distinguishable from zero (0.007 C per decade), but is not falling. But, does that really matter. Does any part of your argument actually hinge on the South Pole cooling while Antarctica in general warms?
2) I'm so glad your vast fount of knowledge has put the American Meteorological Society in its place:
Or possibly you just don't know everything about meteorology, and you got that one wrong.
3) I say that increased CO2 cools the stratosphere by radiating from the stratosphere, not into it.
4) I say that when air moves from a location with high rotational velocity (m/s following a circumference) to a location with a low angular velocity, the air will conserve angular momentum and hence be diverted at right angles to the the initial impetus, resulting (at the poles) in a vortex around the pole. The greater the reduction in rotational velocity of the surface on over which the air is located, the greater the relative velocity of the air to the surface as a result of conserving angular momentum. I think, however, you had figured this out by your post 201.
5) I am not much concerned about your original ozone skepticism. The OP does not claim that decreased ozone cools the surface. Rather it claims that decreased ozone increases the velocity of the circumpolar vortex, thus breaking up pack ice and allowing more ice to form at the surface, thereby contributing to greater sea ice extent. The mechanism for doing this involves cooling of the stratosphere, not the surface. Reduced ozone cools the stratosphere by the very simple mechanism that less ozone results in less UV radiation being absorbed, and hence energy in the stratosphere.
You are welcome to be as skeptical as you like about your straw man. It just has no relevance to the topic discussed on this thread.
http://i.imwx.com/web/multimedia/images/blog/antarctica_wind_pattern.jpg
South polar high, as I said. Winds go towards the sea, rotation of the earth to the east causes the wind to turn west to make polar easterlies.
Most papers on the subject state that the south pole, and much of Antarctica, are cooling. Study the following chart from NASA:
http://www.hyzercreek.com/nasa2005.jpg
The original explanation of how ozone is causing the south pole to cool is wrong, since the ozone level is not changing, (it is already at zero), and yet the south pole is cooling. Your attempt to tweak the ozone hole explanation with a new twist also does not work...you say the ozone fails to absorb UV in the stratosphere, causing more sea ice to form in the winter. This is impossible, because there is no sunlight at the south pole in the winter, and therefore no UV.
http://i.imwx.com/web/multimedia/images/blog/antarctica_wind_pattern.jpg
Listen to me closely. Look at the above link and notice that the vortex has its center over the south pole and is blowing outward, not inward. Polar cooling of the air in winter causes high pressure which sends frigid air north along the surface. At the pole the air has almost no angular momentum, so as it moves north it will not spin as in a vortex. Rather, as the air moves north, the west-to-east rotation of the earth underneath it becomes increasingly fast, making the air blow to the west relative to the earth even though the air itself has little motion. These are referred to in the literature as polar easterlies. They are not really a cyclone because they are caused by the rotation of the earth, not conservation of angular momentum. 200 miles from the pole the earth is rotating around 50 MPH but 1000 miles from the pole the earth is rotation 250 miles per hour. You can see the winds can become frighteningly fast fairly quickly.
The colder the pole, the stronger the high, and the faster the northward motion of the air, and the sooner it can get north before picking up angular momentum from the friction against earth's surface. Therefore, the colder the pole, the stronger the polar easterlies will be. The increase in the polar easterlies is caused by increasing cold. Therefore, the increase in sea ice is caused by increasing cold at the pole. Therefore, we need to know why the pole is getting colder. It's not a straw man to mention the O3 hole, since we need to know whether it's cooling due to the ozone hole, or whether it's cooling because AGW is a false hypothesis.
This web site is for skeptics of skeptics. All the skeptics are saying the antarctic sea ice is increasing because it's getting colder down there, and there is no AGW. Skeptics of skeptics are saying.....Some are saying, ok the south pole is getting colder but it's from the ozone hole. Some (this OP) are saying it's not even getting colder, the sea ice is from the wind, and part of that explanation is to pretend the wind is coming from the wrong direction and saying the south pole is a low pressure vortex. We need to iron this out.
Morgan Wright @204:
1) Of recent papers on Antarctic temperatures all that I have checked show warming. These include not only Steig et al, and O'Donnell et al, but also:
Muto et al (2011), which shows warming of 1 - 1.5 C in East Antarctica, most of which has been in the last two decades.
Bromwich et al (2013), which shows "Central West Antarctica [to be] among the most rapidly warming regions on Earth".
Screen and Simmonds (2012), which shows mid tropospheric warming and stratospheric cooling over all of Antarctica, with the stratospheric cooling being concentrated in Spring and Summer.
Schneider et al (2010), which shows a 0.1 C per decade trend averaged over all of Antarctica, with warming strongest in the pensinsular, and second strongest in the West Anarctic spring.
And finally, because your initial comments regarded the South Pole, we have Lazzara et al (2012), who show a cooling trend at the South Pole till about 2000, and a rapid warming trend thereafter:
It should be noted that when the data is extended to include 2012, the trend of the full data sets becomes positive (as previously noted).
So, there is little doubt from recent literature that Antarctica is warming, with most of the warming being in the last two decades, and in West Antarctica. If you have a paper published in the last 5 years that disputes that, I would be interested to see it - but I see no reason to reject recent studies in prefference to older studies, particularly given that the older studies are now obsolete due to the recent rapid warming trend.
2) You are simply wrong about ozone. Ozone has never fallen noticably below 100 Dobson Units in the period of observations:
Your repeated errors on simple matters of fact are very damaging to your case.
You are also wrong to claim the effect cannot occur because it happens in winter when the sun does not reach the pole. That is first, because the effect occurs in the Autumn when sea ice is growing, but when the sun can still reach the pole. It is also because the ozone hole often extends beyond the Antarctic Circle, which together with its high altitude ensures sunlight reaches regions of depleted ozone long after the pole falls into shadow at the surface.
I will respond to your other points later.
Thanks for the graph showing that ozone has not lowered since around 1988, backing up my argument, that it cant be the cause of south pole cooling.
I also read the Lazarra paper you cited, in which he shows that the south pole winter temperatures are decreasing slightly as the south pole summer temperatures increase slightly, but that neither of which is statistically significant. So let's just say the south pole is staying the same, i.e. not warming.
Now, let's iron this whole thing out. South pole, not warming. Rest of earth, warming. The earth is a heat engine where most solar forcing is in the tropics, heated tropical air moving toward the poles, cold air returning toward the tropics to be heated again. So the earth is a heat engine, like a Sterling Engine, and it operates on the difference in forcing at the equator vs the poles.
So, the south pole is not changing, the equator is getting warmer, so the heat engine is getting stronger. That's why there is more polar easterly wind around Antarctica. That's why there is more antarctic sea ice. Has nothing to do with ozone which is just a stupid theory. Drop it. Let's never mention the word ozone again. There is no UV in Antarctica in the winter, almost none in the spring or fall. I'll give you the summer, which is when no sea ice forms. So, ozone has nothing to do with it. Time to burn the straw man.
OK I'm done with this. Case closed. Forget ozone forever, ok?
Morgan,
This is a scientific board. You must refer to the scientific literature or no one will bother with your posts. You have linked to several blog posts, including an unlabeled graph from a frisbie golf site (this one: http://www.hyzercreek.com/nasa2005.jpg). At the same time Tom has linked to a number of peer reviewed publications. Please bring your posts up to the standard used here or stop posting.
You will not convince anyone here with a frisbie golf graph with 2005 in the link. No one cares what your interpretation of the data is. Link to peer reviewed papers that support your view.
Morgan Wright@206: "Now, let's iron this whole thing out. South pole, not warming"
While I realize that this is not peer reviewed, or even strictly speaking a scientific result, it might bear some counter value to the claim above:
"The 2013 winter – the months of June, July and August – will already go down as the warmest such season at the South Pole since records began in 1957. That trend continued into September – now the warmest on record – with four new daily maximum record temperatures falling in the middle of the month."
And while MW does refer to a NASA-produced anomality-picture from 2005 (apparently), there are newer ones, which are showing that the anomality is positive.
So, old information says cooling. New information says warming.
Morgan Wright @204 (cont), I have been a bit confused about my account of the effect, specifically with regard to the location and altitude of the relevant winds. In particular, I thought the relevant winds were those bringing warmth into the upper troposphere of Antarctica, whereas they are those related to bringing warmth to the Antarctic Ocean. To avoid furhter confusion, I think it best that I lay out the observations directly.
First, the winds involved are those bringing warmth along the surface from about 30o to about 60o South:
These result in westerly winds (clockwise around the pole as viewed from below) just above the edge of Antarctica in the region where the seasonal sea ice forms, ie, the west wind drift:
These have been strenthening, and it is their increased speed that is one of the postulated causes of increased Antarctic sea ice.
Gillet and Thompson (2003) show a comparison between the observed increase in westerly strength and that prediced from a model driven only be reductions in ozone set to match observed reductions:
Gillet and Thompson indicate the strongest effect occurs in the spring in the stratosphere, but then propogates downward to summer (summer and autumn according to Turner et al, 2009).
How could ozone drive this pattern?
The west wind drift is formed by air coming south and then rising as it encounters colder air from Antarctica. For it to rise, air above it must disperse, ie, move either north or south. If it does not disperse, the rising air will cause a build up in pressure that will stop further rises in air. The air moving south in turn must fall at or near the south pole in order to make room for more air. That, however, creates a problem. The air moving south is typically of a similar temperature to the surface in Antarctica, or warmer. If it falls, it will be warmed by increase pressure, making it warmer than the surface air. As a result it will not fall any further. Unless upper troposphere are over Antarctica falls to temperatures approximately 6.5o C per km of altitude above the surface, it cannot fall, with the consequence that pressure will build up at altitude stopping further circulation. Therefore the air coming south must be cooled, primarilly by radiation to space. The radiation to space is made less efficient by the existence of a warm stratosphere above the air, generating IR radiation from above, and limiting the net cooling of the upper troposphere. At this stage, reduced ozone results in a cooler stratosphere and more efficient cooling of air in the upper troposphere. Reduced ozone, of course, cools the stratosphere by the simple expedient of reduced absorption of UV radiation from the sun.
It should be evident that increase CO2 should also result in more efficient cooling of the upper troposphere. When the air below this effect is overwhelmed by increased IR radiation from below. But over Antarctica, increased CO2 should also accelerate the circulation of the polar cell, and hence indirectly that of the mid-latitude cell, and with it the west wind drift. Models do in fact show this effect, but show it to be significantly weaker than the effect of reduced ozone.
I'm wondering about Transantarctic mountains, altitude, humidity, dehumidification, increased cloud cover and the creation of more Antarctic ice through this process. This is the process I'm thinking about and I want to know if it's possible or not. Can someone please tell me where this 'theory' goes right or wrong.
The warming earth causes the atmosphere to hold more moisture all the way from the North pole to the south pole. When this moisture reaches Antarctica it's forced to altitude by the Transantarctic mountains.
This rise of moist air across the cold altitudes of the Transantractic mountains causes whatever moisture that remains in the air to create clouds over the TransAntarctic mountains.
These clouds then spread out and reflect the sun dropping temperatures even further causeing even more cloud cover and increased percipitation in the cold zone.
In other words, the TransAntractic mountains are acting as a giant dehumidifier thats causing clouds to further cool an Area of Antarctica along with increased ice creating snow.
Found the article of value in terms of understanding.
The statistic seem obvious, towards,100 Giga tons of Land Ice melt, per annum, will result in 0.2mm in sea level rise, p.a. rough maths and a benchmark.
The trend line in round numbers, seem supported, by scientific evidence.
The overal position of Antartic Ice increasing correct, but peridic in nature, the desalination of the area, and lowers water tempratures, will increase freezing, perhaps minor, but will affect tidal range globally, on an annual basis.
The objective of the article that focuses on land mass ice, being the more significant component, and Sea Ice being an anual effect stated, but not quantified, as the absolute measure being the more important element.
The overall effect being higher sea levels and a slighly greater tidal range, prediction.
http://www.nytimes.com/2014/05/13/science/earth/collapse-of-parts-of-west-antarctica-ice-sheet-has-begun-scientists-say.html?hp&_r=0
"Two papers scheduled for publication this week, in the journals Science and Geophysical Research Letters, attempt to make sense of an accelerated flow of glaciers seen in parts of West Antarctica in recent decades."
"The collapse of large parts of the ice sheet in West Antarctica appears to have begun and is almost certainly unstoppable, with global warming accelerating the pace of the disintegration, two groups of scientists reported Monday."
"The new finding appears to be the fulfillment of a prediction made in 1978 by an eminent glaciologist, John H. Mercer of the Ohio State University. He outlined the uniquely vulnerable nature of the West Antarctic ice sheet and warned that the rapid human release of greenhouse gases posed “a threat of disaster.” He was assailed at the time, but in recent years scientists have been watching with growing concern as events have unfolded in much the way Dr. Mercer predicted. (He died in 1987.)"
Fixed link
I know that all of these scientists are much smarter than me, but there are millions of years of data no one has. It is so easy for all of these scientists to get all caught up in the details they have learned and focus on this fact and that fact, but the truth is they don't know much of anything, no one does!!!! They have a less than miniscule snapshot of what has happened in the last however many years and they are claiming their beliefs in climate change are fact. The earth has warmed and cooled for millions of years. No one knows why it has cooled and heated for those millions of years. As a society we can't even predict the weather with much accuracy, why does anyone believe they can predict what is happening to the earth? So pretentious....
[JH] If I had seen this comment prior to anyone reponding to it, I would have deleted it for being in violation of the SkS Comments Policy.
Geneally speaking, when someone posts a comment that looks like and smells like concern trolling, it would behoove everyone to refrain from responding until a Moderator has had a chance to review the comment and take appropriate action.
b1rdinski:
Assuming your comment survives moderation, as it may well be considered sloganeering, your argument from ignorance (that is, lack of knowledge) is not universalizable.
You may not know what's been going on with paleoclimate. That doesn't mean no one knows.
So instead of asserting with such certainty that "no one knows why it has cooled and heated for those millions of years" - because you are incorrect - how about you start by asking how scientists know what they know? You might even get a helpful answer.
[JH] If I had seen b1rdinski's comment prior to your reponding to it, I would have deleted it for being in violation of the SkS Comments Policy.
Geneally speaking, when someone posts a comment that looks like and smells like concern trolling, it would behoove everyone to refrain from responding until a Moderator has had a chance to review the comment and take appropriate action.
Please let the official Moderators moderate the comment threads.
b1rdinski, this is a thread on Antarctic sea ice. There are many other threads at SkS more appropriate to your concerns.
I'll also point out that the fundamental piece in the theory of anthropogenic global warming is simply the theory of the greenhouse effect (GHE). That theory (the GHE) is one of the strongest science has to offer.
FYI: If you want to avoid having your comments deleted--that is, if you want your voice to be heard--you'll need to show that you're capable of 1) understanding/recognizing the responses people give you and 2) providing evidence to support your claims.
[JH] If I had seen b1rdinski's comment prior to your reponding to it, I would have deleted it for being in violation of the SkS Comments Policy.
Geneally speaking, when someone posts a comment that looks like and smells like concern trolling, it would behoove everyone to refrain from responding until a Moderator has had a chance to review the comment and take appropriate action.
Please let the official Moderators moderate the comment threads.
ugh - "Antarctic land and sea ice"
The Vice news program on HBO had an interesting story of how the Glacial land ice is melting in Greenland at a rapid rate. If Greenland becomes green, and all the land ice melts, can we really expect the sea level to rise by that much?
Anthony,
This SkS thread says tht if Geenland melted it would raise sea level 6 meters. You would expect at least the same amount from Antarctica. Here in Florida a 12 meter sea level rise would inundate 3/4 of the state, home to about 15 million people. Bangladesh would be long gone. That seems like a lot to me. How much is a lot to you?
http://pubs.usgs.gov/fs/fs2-00/
Anthony, check out the sea level rise explorers here and here to see what a few meters or a few dozen meters of SLR mean for agricultural and infrastructural destruction, and population displacement.
I simply ask a factual question as to the basis of the study pointing to 97.1% peer reviwed abstracts. The opening excerpt quantifies the study in the following "...peer-reviewed scientific literature, examining 11 944 climate abstracts from 1991–2011 matching the topics 'global climate change' or 'global warming'. We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming..." - After doing the math - Including the small percent of those that do not support AGW) doesnt this mean that 97.1% of 4014 (or so) abstracts and not 97.1% of the science "community" or scientists agree ?? And if so, in the interest of truth and fact, dont you seek to clarify this within the media so they can more intelligently inform the public ?? - http://iopscience.iop.org/1748-9326/8/2/024024/pdf/1748-9326_8_2_024024.pdf
edaaaa - Please re-post your comment to a thread where it is on topic.
Without reading all the comments, it seems as if the volcanic activity in the area of Antarctica is being significantly underestimated in IPCC circles. They admit there is volcanic activity and if you twist arms one can even get an admission that volcanic activity has been steadily increasing in the antarctic as 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. The pro-AGW answer seems to be "No it's not", or "It is not important." Indeed it is not mentioned in the article above and is ignored in most of the abstracts concerning the Antarctic ice loss. The strongest answer is that warm ocean currents is the much greater contributor. How does this reconcile with record sea ice sheets? Wouldn't warm ocean water trends affect sea ice even more effectively than land ice? I understand that the Antarctic land ice is more important in models, but then why ignore that the region -under the landmass- is warming? Considering that one major volcano can cool the world for decades, it seems that the pro-AGW group is quite dismissive of their power to affect climate change.
Tuerqas, show me a study — any study — that shows Antarctic volcanic activity increasing over the past fifty years.
Further to DSL - a big volcano close to tropics can cool the world for a few years (not decades) because stratospheric aerosols block the sun. A volcanic eruption in the polar regions, especially Antarctic, doesnt distribute aerosols worldwide. Furthermore, dust would blacken the snow, sharply reducing albedo and leading to more melt but there havent been such eruptions in Antarctica.
To the paradox of warm ocean but increasing seaice, see the intermediate version of this article.
To volcanic effects on icesheet losses, note that incoming radiation is measured in watts in summer, (daily mean ~25W/m2 in December) whereas geothermal heat measured in milliwatts. For a calculation on volcanic effect on ice sheet using recently published paper on Thwaites,
see here and for an update which reduces it further, see here