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
I suspect the "water lift" effect might come to dominate in coming years. The underside of the ice shelfs slope upward from their grounding line to the seaward edge of the ice. As this ceiling melts under the influence of slightly warmed sea water, it freshens the water which being lighter, flows oceanward along this upsloping ceiling of ice. As the grounding line becomes deeper and deeper as the ice melts back under a retrograde slope of the ocean bottom, this effect should increase. Of course as the freshened water flows up and out on the surface of the ocean, it pulls sea water in under the ice. An added effect is that the ice melts at lower temperatures at depth so the fresher water may be "super cooled" with respect to the shallow water where it exits the ice shelf. This could be an added explanation for the increase in sea ice as this very cold, somewhat fresher water then comes in contact with Antarctic Night air. These currents may also be pushing the ice outward, opening leads that then freeze over.
Awesome blog. I enjoyed reading your articles. This is truly a great read for me. I have bookmarked it and I am looking forward to reading new articles. Keep up the good work!
"Satellites measure Antarctica is gaining sea ice but losing land ice at an accelerating rate which has implications for sea level rise."
This "argument" is clearly wrong. Antartica is gaining land ice mass and sea Ice. This should be corrected if this site claims to offer science as answers.
http://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses
"Update Nov. 7 2015
A study published by Jay Zwally and his team on Oct. 30 (Zwally et al. 2015) has suggested that until 2008 there might have been a bigger increase in ice on East Antarctica than there is a decrease in the west, meaning that total Antarctic land ice is increasing."
There is nothing in that study to suggest that he ice gain that has been occurring for 10,000 years has stopped.
The Science has shown that Antarctica is gaining ice. Clinging to this false claim that the "science says" Antarctica is losing land ice shows poor alligiance to science.
There are a whole bunch of studies that show the Antarctic (land-based) ice sheet is losing mass versus Zwally's study that claims otherwise. Zwally's work is currently incompatible with Holocene sea level history and recent assessments of the sea level budget.
So there's a considerable volume of scientific work arguing against it. We'll just have to wait and see if Zwally's work stands up to scrutiny. If it does, we will change the text accordingly. Changing it now would be premature.
As for Antarctic sea ice, that's very interesting and very likely related to the wind trends and their effect on the polar gyres. SkS will have a new post on that in a few weeks.
Iceman
Here is the latest sea ice extent for Antarctica.
Fairly low for this time of year.
Yes there has been some increase in the maximum in recent years. But we will have to wait and see as to whether that is an ongoing increase or not.
And Rob is right, The Zwally paper is new and is an outlier result compared to other studies. Too early to assess whether it will stand or not.
That should read "Table 5" not "Table 10"
Maybe someone could help me understand. Antarctic ice? If the land ice is melting but the sea ice is increasing, don't we have two separate causes? It don't understand how you can have both with the same environment.
Anecdote: When the glacier covered Maine the plate was 200 feet below sea level. The glacier melted away ( from global warming?? ) and the land plate floated up and is now 4 feet above sea level. Or did the sea level fall because the land mass moved up. I am sure someone out there could explain this to me. please!
It seems to me when a tectonic plate looses massive amounts of weight ( ice ) in this case, it makes sense that it might move up because it is floating on magma ( or something like that ).
I also wonder about wind mills too. If our "climate" is dependent on air streams; based on earth rotation and adiabatic rise, then if we take the heat ( energy ) out of the wind we have not, will that not affect the wind currents driving our local climates?
B14
" don't we have two separate causes?" Yep. Maybe more than 2.
Sea Ice has increased a little in the last few years although mainly at the maximum in winter. This year, at the summer minimum it is rather low. Drivers of sea ice extent? Possible changes in sea water salinity, changing the freezing point of the water. Changes in the winds around Antarctica, driving more spreading of the ice and freezing over of the open water created. The wind patterns may have changed due to a combination of the current Pacific Decadal Oscillation which has now started changing, and the ozone hole allowing more sunlight to reach the surface rather than being absorbed in the stratosphere; the extra energy from this may have accelerated the winds.
In Antarctica land ice doesn't melt much - it is too cold. Rather it flows slowly to the coast and eventually breaks off as icebergs. Factors changing this? Ice sheet breakup. Floating ice sheets (not seasonal sea ice) act as buttresses, slowing the speed with which land ice can flow. Some have broken up. Grounding line retreat. This applies particularly in West Antarctica where the 'land ice' is actually sitting on the sea floor 100's and even 1-2000 meters below sea level. Sea water intrusion at the grounding line is causing some retreat of the grounding line, so that ice that was grounded ends up floating, and easier for icebergs to break off. The key here is what is happening to sea water temperatures at the base of these sheets, 100's of meters down. This in turn can depend on differences in what is happening to different currents at different depths.
Some recent research also suggests there is a critical threshold wrt the height of ice cliffs. It seems ice when it contains cracks isn't strong enough to allow ice cliffs to rise much more than 100 meters above sea level. Otherwise it breaks off. Then buoyancy of the remaining submerged ice can then break that off from the main ice cap.
Ice is way more complicated than just melting and freezing.
In reality, Arctic sea ice is at a record low and global sea ice is diminishing.
NASA LINK
NATURE LINK
NSIDC LINK
Further, Antarctic sea ice is shrinking, now statistically indistinguishable from the long-term average:
LINK, showing current extent of Antarctic sea ice
NSIDC LINK
Hi -
I have found this thread helpful to getting perspective on land and sea ice discussion. My comment is a question or request about data:
For a long time I have been trying to monitor land ice, but for the layman the information does not seem to be readily out there and updating regularly. I see this page:
https://climate.nasa.gov/vital-signs/land-ice/
However, that information has not been updated past March 2016. I've tried to dig around a bit for alterntaive sources of information and haven't so far been able to find any. I don't know if it is the function of this page to provide such information, but does anyone know of a good source that can readily be understood by non-scientists? (To get an updated reading of whether trends in Antarctica toward lower land ice are continuing).
Should this discussion be updated to account for the recent record lows in Antarctica's sea ice extent?
jlsoaz: Did you look at the National Snow & Ice Data Center's website, nsidc.org?
Hi amhartley:
Thanks for the response.
Yes, I have been to nsidc.org a fair amount, particularly this page to try to understand each Northern Hemisphere summer what is going on with greenland ice melt:
http://nsidc.org/greenland-today/
While I do like that page, I must say I have not been able to find what I am looking for there, as far as clear non-scientist-oriented data that shows land ice changes over the years, whether for the Antarctic, Greenland or other places.
The NASA site I mentioned in my post above seems to show land ice mass changes.
https://climate.nasa.gov/vital-signs/land-ice/
and it cites two sources:
https://grace.jpl.nasa.gov
https://www.nasa.gov/mission_pages/icebridge/index.html#.VDQh8UvLxd0
There seems to be (as best I can make out) a common theme to both sources that they were satellite-based systems, with IceSat gone and GRACE no longer functioning fully, and both systems seem to have scheduled replacements. (Maybe I am confused and they are one and the same system, but it seems like possibly different systems and different planned replacements).
https://en.wikipedia.org/wiki/Operation_IceBridge
https://en.wikipedia.org/wiki/ICESat-2
https://en.wikipedia.org/wiki/Gravity_Recovery_and_Climate_Experiment#GRACE_follow-on
Perhaps it is the somewhat challenging nature of the science journalism involved, but I haven't seen a single news story which gets at the important question of how important this land ice data would seem to be, that no widely-disseminated information seems to be available dating past 14 months ago, and that both sources are dependent on expensive new planned launches which we can hope won't be pushed back or cancelled, but which are still 2-3 quarters away at the least.
Perhaps the IceBridge interim plane-based system can provide data, or perhaps other countries or systems are developing data? Japan? China? NASA has literally labeled this as a "vital sign" and it does seem important, so I'm hoping to uncover if there is more reliable data out there. Perhaps I have missed something at NSIDC. Do you have a specific link in mind?
It sounds to the outsider as though it is very important to you guys to say that the addition of ice in Antarctica is NOT due to global warming, a separate issue related to Ozone (are humans responsible for the Ozone hole?). But the loss of ice is due to global warming.
Seems to me addition of ice is a simple thing to say, and that attributing it to something else is kind of like saying this ice is different from that ice, that some ice counts toward the ice in Antarctica and some doesn't count.
And you sound awefully sure about that Ozone hole, Where are the references to the studies that prove lack of Ozone is the problem? Well, is there a problem that Ozone ice is messing up something in Antarctica? Should be plug the Ozone hole?
Let's just say Ice overall is growing in Antarctica, okay?
compx2,
I think time has caught up with your comment "Let's just say Ice overall is growing in Antarctica, okay?" which is now twenty months out of date.
Overall, the Antarctic ice cap was certainly not "growing" ice-wise over the period 2002-16. (The Zwally theorising mentioned in the OP update is an interesting theory but nothing more.) And the Antarctic Sea Ice had been showing a slow rise in SIE over the satellite record 1978-2010 and then did show a dramatic upward wobble to early 2016. But since then, as the comment @463 pointed out, the drama has been in the opposite direction and now SIE continues lower than at any time earlier than 2016.
I've written on the Zwally paper and its shortcomings, here.
Part of your explanation for increasing ice in the Antarctic is that it's getting colder, and then you go on to say that it's actually getting warmer and that ice is decreasing, so which is it?
"i) Ozone levels over Antarctica have dropped causing stratospheric cooling and increasing winds which lead to more areas of open water that can be frozen (Gillet 2003, Thompson 2002, Turner 2009)."
"You're also correct in pointing out that snow accumulating in the East Antarctic interior is increasing, presumably due to increased precipitation caused by more humid conditions caused by warming air."
[JH] Please specify which "ice" you are referring to. Is it sea ice in the oceans surrounding the Antarctic continent, or is it glacial ice formed on the continent itself?
matt - as per JH comment, you need to take notice as to which ice you are talking about. Sea ice extent appears to be influenced by katabatic winds bring cold air from the interior over the surrounding sea. These increase outward dispersion of sea-ice was well as freezing the surface so you can increase seaice extent despite a warming ocean as per papers cited in article. The strength of the katabatic winds seems to be influenced by the ozone levels in the stratosphere. However, more observations are needed before this can established with certainity.
Land ice is a more complex picture. Early models (TAR I think), predicted Antarctic land ice would increase as warming seas resulted in more moisture being blown over Antarctica and falling as snow. However, this is balanced by substantial ice sheet losses on margins especially in West Antarctica as calving rates accelerate. You can see the pictures/videos of land ice mass change over here. Broadly it is mass gain around EAIS and mass loss of WAIS, with overall net mass loss.
I watch the video from years ago and giggle... "The unexpectedly rapid loss of land ice..." Assuming the maximum temps projected by the IPCC does this young man understand how long it would take for a even a 10% melt? Even during the most rapid ocean rise scenarios things will be just fine... The sky is not falling. How about helping the developing countries develop and solve an ongoing humanitarian crisis now that oh by the way is truly polluting the environment?
[TD] That video from "years ago" was made only 2.5 years ago. In my response to your previous comment I gave you a link to a Scientific American article that references studies from last year, which you could read if you were sincerely interested in learning. That "young man" in the video was a PhD candidate with a large number of peer reviewed professional publications directly relevant to the topic he was speaking about in that video. (A remarkable number of publications for a PhD student!) Now he is a postdoctoral fellow. His degrees and postdoc all are directly relevant: physical geography, geomatics, spatial analysis, glaciology, permafrost science, and northern environmental change.
Meanwhile you claim you are "working on" a PhD and have failed to respond to the specific counters to your claims that I already provided.
The percent of land ice melt is not relevant. What matters is the absolute amount of water released by the melt. Someone actually enrolled in a PhD program in planetary geology would know that.
Read the post about how much sea level will rise. After you read the Basic tabbed pane, read the Intermediate one. Watch the two videos. Then read professional statistician (multiple peer reviewed publications on climate change) Tamino's explanation of a new paper supporting the existence of sea level rise acceleration so much that by the year 2100 sea level would be .654 meters higher than in 2005, supporting the projections of IPCC AR5's RCP 8.5. Then explore the Surging Seas site to see the concrete, practical implications of that amount of rise, but keep in mind that the amount of rise could be double that .654 meters which was only extrapolated from observations up to now, because the current acceleration easily could increase. Then explore the US Geological Surveys site on sea level. If you really are enrolled in a PhD program, you should be able to handle the AR5 WG1's Chapter 13 on Sea Level Change. To learn about impacts, adaptation, and vulnerability, read WG2's report.
Fishfear
According to the most recent summary by the US Global Climate Change Research Program, the official report of the Trump administration, for sea level "A rise of as much as 8 feet by 2100 cannot be ruled out." That would cause a loss of more than a trillion dollars of real estate in Miami alone. World wide hundreds of millions of peoples homes would be washed away.
Your unsupported claim that " Even during the most rapid ocean rise scenarios things will be just fine..." is simply false.
According to the National Snow and Ice Data Center, the sea ice around Antarctica has set record lows each of the past two years. The land ice is declining at an increasig rate according to gravity measurements.
Your claims are all simply false. Please provide evidence to support your wild claims.
Hmm, if you are fixating on a outlier paper (Zwally 2015), then I suspect you are using extremely suspect sources for your information. Gravity and altimitry methods both have weaknesses (but different ones). A clever approach which reconciles the metholodies by a joint inversion of altmetry, gravity and GPS is Espanol et al 2016. Their approach demonstrates a sustained net mass loss of 84+/- 22 Gt/yr.
"How about helping the developing countries develop and solve an ongoing humanitarian crisis now that oh by the way is truly polluting the environment?" Why do you believe fixing climate (which is important way to help developing countries) is incompatiable with your perceived priorities?
And just a reminder, that on this site, you must provide references to support your beliefs. Otherwise you will be moderated for sloganeering.
Let's look at that:
Zwally et al 2015 took an unconventional approach to assessing the mass balance of Antarctica. Unlike other studies, before and since, that used satellite altimetry or satellite gravimetric methods, Zwally’s team chose to compare net snowfall accumulation to estimated ice discharge to the ocean in a dataset that ended in 2008. In order to do this type of analysis properly, 3 main things are needed:
1. It is critical to use the most optimal corrections for instrument biases (the ICESat data used need to have the appropriate saturation bias corrections to get real-world answers that are reproducible)
2. The most-accurate densities of snow have to be used
3. The most-optimal values for changes in bedrock elevation (GIA) in response to ice sheet mass changes have to be used
As has been since determined by multiple studies (A, B, C, D, E, F and G, listed following):
1. The ICESat bias corrections used by the Zwally team were appropriate for measuring sea ice, but not for measuring high altitude land-base ice sheets like found in Antarctica (the values returned for Lake Vostok alone were so unphysical that they should have made the entire study DOA)
2. A value for snowfall density different than that determined by decades of land-based research was used
3. The values used by the Zwally team to correct for GIA were too high by a factor of 2
As such, their results cannot be reproduced using well-established bias corrections, known snow densities and more appropriate values for GIA.
Looking at even more recent studies, per Gardner et al 2018:
Results from the recent IMBIE Team from 2018 show that Antarctic ice sheet mass losses are accelerating, tripling their contribution to global sea level rise since 2012.
Lastly, Bamber et al 2018 subtly but firmly savages Zwally et al 2015:
The values for the Antarctic ice sheet mass balance from NASA GRACE are the most current available (to January 2017). An ever-strengthening, consilient body of research using multiple methods all point to that conclusion.
Reference studies:
A. Scambos et al 2016 Comment on Zwally et al 2015
B. Martín-Español et al 2016 - Spatial and temporal Antarctic Ice Sheet mass trends, glacio-isostatic adjustment, and surface processes from a joint inversion of satellite altimeter, gravity, and GPS data
C. Schröder et al 2017 - Validation of satellite altimetry by kinematic GNSS in central East Antarctica
D. Martín-Español et al 2017 - Constraining the mass balance of East Antarctica
E. Gardner et al 2018 - Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years
F. The IMBIE Team 2018 - Mass balance of the Antarctic Ice Sheet from 1992 to 2017
G. Bamber et al 2018 - The land ice contribution to sea level during the satellite era
Interestingly, previous research has shown that ice sheet mass contributions from land-based ice sheets have exceeded thermal expansion as the biggest contributor to global sea level rise. Recent research now has isolated the individual ice sheet contributions to global sea level rise.
Per Hsu and Velicogna 2017, between April 2002 and October 2014, the mass component of global mean sea level grew by about 1.8 millimeters per year, with 43 percent of the increased water mass coming from Greenland, 16 percent from Antarctica, and 30 percent from mountain glaciers. There is an additional ~1 mm per year of SLR coming from thermal expansion (H/T to Victor Zlotnicki).
[DB] Edited to add references to sources E, F and G.
A team of international scientists is due to set off for the world’s biggest iceberg ,fighting huge waves and the encroaching Antarctic winter ,in a mission aiming to answer fundamental questions about the impact of climate change in the polar regions.The scientists, led by the British Antarctic Survey (BAS), are trying to reach a newly revealed ecosystem that had been hidden for 120,000 years below the Larsen C ice shelf on the Antarctic peninsula.In July last year, part of the Larsen C ice shelf calved away, forming a huge iceberg - A68 - which is four times bigger than London, and revealing life beneath for the first time.
The climate change had already affected the seas around Antarctica and is warming some coastal waters.So now both Antarctic Peninsula and West Antarctica Ice sheet are losing ice.For now, the East Antarctic Ice sheet is stable but it will influence on global climate change due to sea ice.In the future there is growing concern about the possible impact of climate change.Is Antarctica gaining ice that meant it will effect to climate change and the ecosystem of the regions?