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Is Antarctica losing or gaining ice?

What the science says...

Select a level... Basic Intermediate

Antarctic sea ice is gaining sea ice but Antarctica is losing land ice at an accelerating rate, which has implications for sea level rise.

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)

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, bu 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 (Gillet 2003, Thompson 2002, Turner 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, Bintanga 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. 

Shepherd et al. 2017

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.


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. 

Basic rebuttal written by mattking

Update July 2015:

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial


Last updated on 31 January 2020 by BaerbelW . View Archives

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Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Further reading

Tamino compares and analyses the long term trends in sea ice data from the Northern and Southern Hemisphere in Sea Ice, North and South, Then and Now.


On 20 Jan 2012, we revised this article upon learning it referenced an incorrect quote. We apologize to Dr. Michaels and to our readers for the error.


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Comments 451 to 500 out of 509:

  1. 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.

  2. 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!

  3. "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.

  4. "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. 

  5. 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.    

  6. 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.

  7. That Zwally paper is interesting. Set aside the matter of the total mass change for a moment, and look at the changes between 1992-2001 and 2003-2008, the delta column in Table 10 or by eyeball from Fig 9. Mass waste in PIG, Thwaites and neighbours had doubled in the periods covered in the paper, the you can see the hole burning toward Ross, Ronne and the Transantarctic mountains. Recall that we are now in 2016. So apart from an overall constant, the trends agree. Fig 9 indicates that Totten is another place to watch, and I am glad the Amery doesn't seem to be waking up, at least in this data.
  8. That should read "Table 5" not "Table 10"

  9. 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?

  10. 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.

  11. "Antarctic ice? If the land ice is melting but the sea ice is increasing"

    In reality, Arctic sea ice is at a record low and global sea ice is diminishing.

    "Sea ice increases in Antarctica do not make up for the accelerated Arctic sea ice loss of the last decades, a new NASA study finds. As a whole, the planet has been shedding sea ice at an average annual rate of 13,500 square miles (35,000 square kilometers) since 1979, the equivalent of losing an area of sea ice larger than the state of Maryland every year."

    “Even though Antarctic sea ice reached a new record maximum this past September, global sea ice is still decreasing,” said Claire Parkinson, author of the study and climate scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “That’s because the decreases in Arctic sea ice far exceed the increases in Antarctic sea ice.”

    “When I give public lectures or talk with random people interested in the topic, often somebody will say something in the order of ‘well, the ice is decreasing in the Arctic but it’s increasing in the Antarctic, so don’t they cancel out?’” Parkinson said. “The answer is no, they don’t cancel out.”


    Further, Antarctic sea ice is shrinking, now statistically indistinguishable from the long-term average:

    LINK, showing current extent of Antarctic sea ice


  12. 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:

    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).

  13. 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,

  14. Hi amhartley:

    Thanks for the response.

    Yes, I have been to a fair amount, particularly this page to try to understand each Northern Hemisphere summer what is going on with greenland ice melt:

    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.

    and it cites two sources:

    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).

    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?

  15. 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?

  16. 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.

    Jaxa SIE 1978-2016

  17. I've written on the Zwally paper and its shortcomings, here.

  18. 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?

  19. 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.

  20. 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.

  21. 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.

  22. 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?

  23. And just a reminder, that on this site, you must provide references to support your beliefs. Otherwise you will be moderated for sloganeering.

  24. "a outlier paper (Zwally 2015)"

    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:

    "Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 183 ± 94 Gt yr−1 between 2008 and 2015."

    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.

    Antarctic ice sheet contributions to SLR

    Lastly, Bamber et al 2018 subtly but firmly savages Zwally et al 2015:

    "Issues with the approach used for calibration of the altimetry by Zwally et al have been identified (Scambos and Shuman 2016) and an attempt to replicate the trends using similar assumptions for the physical mechanism could not reproduce the large positive balance they found (Mart´ın-Espanol ̃ et al 2017). For these reasons, we believe that the estimates from this study are likely erroneous"

    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.

  25. 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?

  26. Worth noting that there is now comprehensive review published here concluding "it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). "

    More importantly, it discusses the reasons behind the different estimates and why the variation, especially with ICESet altimetry data.

  27. Daniel Bailey, thanks for that summary, that was helpful.


    [DB]  You're very welcome!  I added some additional sources and explanatory texts to my comment above.

  28. Anyone hear anything about how much of the melting West Antarctic land ice is due to geothermal/volcanism versus the warming climate?  

  29. Ed @478, take a look at the comments at this SkS post from 2014: Ice Picks: Five pieces of ice news...

    You may want to look at the comments at a RealClimate post from the same time. Specifically this one (#179).

    The upshot is that not much of the melting in West Antarctica is due to geothermal heat flux.

  30. Thanks David.  It's difficult to find any hard quantitative data.  I don't see much in the references you provide.  


    I did did a quick search and found a few more articles, one an actual journal paper with more recent information:

  31. PS: It's important to note that according to the above sources glacial meltwater isn't the only contribution of the geothermally warm area that affects sea level.  The meltwater essentially lubricates the accelerated motion of the ice flowing into the ocean.


    [DB] From Cazenave et al 2018, the various contributions to SLR from 1993-2015:


    And from 2005-2015:


  32. The Realclimate comment does the calculation to show how small the geothermal component is, even with ridiculously unphysical assumptions. Furthermore, if you look at the references behind your links, you will note the important comment that geothermal flux is not increasing - there are physical constraints around the rock properties in play. When you are looking at change in Antarctica, geothermal influence isnt important.

    The biggest player in Antarctica is the loss of the buttressing ice shelves undermined by warming adjacent ocean (see also here), which speeds glacial loss.

  33. The influence of near-surface winds, in particular steered by extratropical cyclones or anti-cyclones, has recently received renewed attension. As much of the sea-ice is guided by near-surface winds, anomalously strong offshore winds can act to reduce the seasonal retreat of sea ice (it can also act the other way round). This influence of the wind as a mechanical driver of changes in sea-ice extend is comparable to the associated thermodynamic influence via warm and cold-air advection onshore/offshore Antarctica (1). 

    Regional changes in the frequencies and intensities of different weather types, weather patterns, the associated storm tracks and related phenomena, like weather fronts, to a global-scale warming is highly complex and display no homogeneous increase. The local anomalies of the sea-ice extend during the melt season is even coupled to anomalous winds during the previous sea-ice growth season, which affects the sea-ice growth rate and acts as initial condition for the  anomalies seen in sea-ice extend during the next season. The sea-ice extend anomalies are not directly/instantaneously connected in space and time to wind anomalies (2,3,4).

    Nonetheless,  studies have found trends in number of extratropical cyclones and anticyclones that agree with those seen in Antarctica sea-ice extend, across space and time and not suprisingly, the changes in the frequency of weather systems and related wind exhibit high spatial variability (4).

    Assuming a homogenous decrease of sea ice in response to global warming is a clear over simplification as the intermediate scale, the weather scale, and its response to a hemispheric-wide mean warming trends is highly non-linear in space and time. There is clear tendency by critics to discount/ignore the influence of the wind as a mechanical driver underlying the observed sea-ice trends and focus purely on a simplified thermodynamic local response.


    (1) Holland, P. R., & Kwok, R. (2012). Wind-driven trends in Antarctic sea ice drift. Nature Geoscience, 5, 872–875.

    (2) Holland, M. M., Landrum, L., Raphael, M., & Stammerjohn, S. (2017). Springtime winds drive Ross sea ice variability and change in the following autumn. Nature Communications, 8, 731.

    (3) Holland, P. R. (2014). The seasonality of Antarctic sea ice trends. Geophysical Research Letters, 41, 4230–4237.

    (4) Schemm, S. (2018). Regional trends in weather systems help explain Antarctic sea ice trends. Geophysical Research Letters, 45.

  34. It seems the melting of the land ice of the west coast has to be found in the volcanoes that have been discovered not in the human activity. A 2017 study claimed to have found 138 volcanoes, of which 91 were previously unknown. See :

  35. Roque @484 ,

    you can get more information from the University of Washington, which studies this area.

    If I understand it correctly, there was no suggestion that the 91 previously unknown volcanoes were new (i.e. producing additional new heat to melt the overlying ice).   So presumably all the local volcanoes have been producing heat for thousands of years ~ not much changed over the 5-6000 years demonstrated in the glacial records there.

    But do note that there is a possibility that, as AGW causes more melting, there will be less weight of ice pressing down on the volcanic areas . . . and the volcanoes might therefore be able to increase their activity in the future (contributing to even faster ice melt & sea-level rise over an uncertain period).   This is just one more of the uncertainties about rate of sea-level rise over the next century or more.

  36. Vulcanism has been present in Antarctica for well over 50 million years.

    The ice sheet there formed 34 million years ago, and persisted since, in spite of that vulcanism. A subglacial heat mantle plume would have produced detectable subglacial drainage and melting events. None has been detected for the Pine Island Glacier and the adjacent Thwaites Glacier has proven largely insensitive to the presence of such a mantle heat source:

    "volcanic heat does not contribute significantly to the glacial melt observed in the ocean at the front of the ice shelf"


    "the heat source beneath the Pine Island Glacier is roughly 25 times greater than the bulk heat flux from an individual dormant volcano"

    The heat coming from the geothermal activities under the ice is not a whole lot more than that coming from a dormant volcano.

    People walk on dormant volcanoes. Trees grow on them.

    In Antarctica, ice forms on them.


    Marie Byrd Land

    The volcanic heat plume mentioned under the ice of a portion of Antarctica is fossil heat; its last activity predates the formation of the Antarctic Ice Sheet (itself more than 34 million years old).

    "The plume is far older than the recent period of atmospheric warming; indeed, at 50 million to 110 million years old, it's older than our species and the West Antarctic Ice Sheet itself."

    So the ice in the area formed anyway, in spite of the supposed "volcano".

    Influence of a West Antarctic mantle plume on ice sheet basal conditions

  37. I believe that there are observable changes in the natural environment (such as ice-caps melting and sea-level changes), and that these are due to climate change. But I think denial of such things is probably bad science, and promoted by bad skeptics. It's not fair to characterise all "skeptics" as all having such beliefs.

    The better scientific case against "climate change" is that it's not human causes, but natural causes, that are responsible for the bulk or entirety of these changes. The climate changes naturally and always has. The true question is -what is causing that change-?

    AGW promoters say CO2. "Skeptics" say natural factors such as Milankovitch cycles, solar radiation cycles, and the circumpolar vortex.

    Sherwood Idso, in a 1998 paper, presents a case, based on results from eight natural experiments, that the influence of CO2 on the temperature, through the greenhouse effect is minimal - he derives an upper limit of 0.4 degrees C for a 300 to 600 ppm doubling of atmospheric CO2. Piers Corbyn also believes that the influence of CO2 on climate is minimal/insignificant.


    [PS] Past climate change was most certainly from natural well-understood causes, but that is irrelevant to today because those natural causes should be cooling us. If you are a genuine skeptic try applying that to Sherwood and Corbyn and see if you can spot the errors and downright misleading information yourself.

  38. Jesscars @487 , if you go to the well-known website WUWT [WhatsUpWithThat] you will find that "skeptics" have all sorts of beliefs about climate-change / global-warming.  And these beliefs are mostly mutually contradictory.

    A few hold beliefs that are quite reasonable ~ at least, for the conditions prior to the industrial-revolution / coal-burning.   Others believe that the [observed & well-documented] ice-melt & sea level rise are simply not happening ~ are a hoax (from a two-century conspiracy by corrupt scientists worldwide . . . a conspiracy without even a single whistle-blower ! )    Others believe that "chemtrails" are being sprayed by the Lizard People (disguised as humans) in order to befuddle and subdue the human race . . . leading to a dictatorship by an Anti-Christ or alternatively a Marxist World Government (run by the Illuminati or similar).

    Half are in complete denial CO2 has any physical effect whatsoever (other than nourishing plants).   Others think the atmospheric CO2 effect is low but negligible, and that we can keep merrily burning coal/oil until it's all used up.   Yet others think (despite the evidence) that all global warming/cooling comes from oceanic overturning cycles of 1400 years' duration (or whatever).   Or believe that the the orbits of Jupiter & Saturn are the underlying cause of climate change . . . or that Galactic Cosmic Rays are the sole responsible factor.   In short : ABCD  (Anything But Carbon Dioxide) .

    But what say you, Jesscars ?

    # Probably simpler for you to answer here , rather than on all the other six threads you have posted in over this afternoon.

    # Also, please don't bother to mention Idso & Corbyn ~ since those two gentlemen have failed at basic arithmetic.

  39. If you semi inflate a soccer ball then put it on the floor with a weight on it , it will deform to roughly the same shape as the earth. Take the weight off and the ball becomes more of a globe shape rather than a flattened pear. When the localised weight of the Antarctic ice is removed, what happens to the rest  of our connected planet . My bet is that this will give rise to a global redistribution of surface tension and an associated rise in tectonic and volcanic activity. Also possibly the weight of other continental plates will cause them to sink lower than their present position re the geoid and thus contribute to an increase in apparent sea level rise caused by continental sink. Thoughts?

  40. Ataluma @489,

    Concerning ther seismological part of your comment, a 2012 book 'Waking the Giant: How a Changing Climate Triggers Earthquakes, Tsunamis, and Volcanoes' by Bill McGuire has a CarbonBrief assessment here.

  41. MA Rodger@490, thanks for the info re Bill McGuire. Cheers

  42. My understanding is that the GRACE satellite shows that Antarctica was been losing mass throughout the years during which Zwally showed increases in sea ice extent. Since ice extent is a 2D measure, it can't acocunt for ice thickness the way GRACE gravity wave measurements can. 

    I'm not sure where to find the newest data from GRACE-FO, which llaunched in May, 2018 (I couldn't interpret it, anyway), but I am interested to see how the continent's mass has changed in recent years.

  43. icowrich @492,

    GRACE did show a loss of Antarctic ice mass 2002-16 as the NASA graphic below illustrates. We all await the GRACE-FO data (which should soon start appearing here). The numbers are now being published (here) but so far only in a form that will require a bit of processing to show the sort of data graphed out below.

    Note this is all land ice. Sea ice floats so is invisible to GRACE.

    NASA Antarctic GRACE graphic

    The work by Zwally (that I know of) also did not concern Antarctic Sea Ice, Sea Ice Extent or otherwise. Mind, satellite data did show a small increase 1979-2015 in Antarctic Sea Ice Extent but that dramatically turned into a decrease 2015-17 - as graphed here - (usually 2 clicks to 'download your attachment').

    Zwally et al (2015) concerned analysis of the land ice and the altitude of the ice surface. This showed an increase in altitude suggesting an increase in ice mass. The controversy revolved around levels of snowfall and the process of snow-compaction-into-ice as well as canculation of data uncertainties. It had some merit but obviously the GRACE data is a very strong counter-argument which makes the controversy more academic than a battle over results.

  44. Recommended supplemental reading:

    ‘Extraordinary thinning’ of ice sheets revealed deep inside Antarctica by Damian Carrington, Environment, Guardian, May 16, 2019

    Antarctic instability 'is spreading' by Jonathan Amos, Science & Environment, BBC News, May 16, 2019

    Precipitous' fall in Antarctic sea ice since 2014 revealed by Damian Carrington, Environment, Guardian, July 1, 2019

    Glacial melting in Antarctica may become irreversible by Adam Morton, Environment, Guardian, July 9, 2019

  45. Comment 475 and its references are very helpful. Comment 452 is undoubtedly spam!

    Zwally (2015) is still doing the rounds on social media, although there seems to have been much research reconciling it since. I also found the Scambos & Shuman comment, Martin‐Español et al (2017) (press release here), IMBIE (2018) highlighting the possible range of East Antarctica loss or gain, and then a couple for 2019 not directly linked in these comments so far:

    The Scientific American article "What to Believe in Antarctica’s Great Ice Debate" by Shannon Hall says 'Most scientists agree that East Antarctica—unlike its western counterpart—is gaining mass in the form of snowfall or ice'. I notice that Shepherd et al agrees with that (East Antarctica subtracting 1.1 ± 0.4mm sea level rise since 1992), but Rignot at al says E Antarctica has contributed 4.4 ± 0.9 mm in the same period. All the above agree that Antarctica as a whole is losing mass (mostly from glacier flow into the sea), but one study says three times more than the other.

  46. How can sea ice increase and land ice decrease at the same time?


    [DB]  Both Arctic sea ice and Antarctic sea ice daily extents are currently well-below the long term average of all decades prior since 1979.  Land-based ice continues to be lost with losses increasing in recent decades.  See here, here, herehere and here.

    Antarctic SIE

    Arctic SIE

    Combined Sea Ice Extents

  47. Hi,

    How did you get the impression that sea ice is increasing?

  48. Hi. While the current situation has seaice decreasing, it is entirely possibly to have increased melt from ice sheet and increasing sea ice. This was the situation a few years ago. Drivers for both sea and land ice are different between Antarctica and Arctic due to the major geogeographic difference - Antarctica is a continent, 2000m high at pole, surrounded entirely by ocean whereas the arctic is a landlocked sea. Sea ice in the Antarctic responds to a complex set of factors which have quite a lot variability. See this post for more detail. We could easily have a return to increasing seaice. However, the very long term trend is likely to be reduction as the warming sea temperature dominate,  over wind-driven dispersal and decreased saliinity. The decrease in ozone loss should also reduce wind dispersal.

  49. Hi,

    This myth is a little old now.  Five or more years ago for a few years there was relatively high sea ice in the Antarctic.  The record is not very long, only since 1979.  Deniers claimed that since sea ice in the Antarctic was high, warming could not be occuring.  In the past four or five years the ice area in the Antarctic has collapsed to the lowest in the record.  This myth has gone out of fashion since now Antarctic sea ice is low.  Land ice is also melting in the Antarctic.

    To answer your question:  It is believed that sea ice area in the Antarctic is strongly affected by winds.  If there are a lot of offshore winds then new ice freezes near shore as existing ice is blown out to sea.  Strong winds thus increase sea ice area.  Around 2010 the winds in the Antarctic were stronger offshore than they had been before that time.  It is not completely clear why the winds were stronger.  It may have been due to natural variation or it may have been due to some climate change affect or the result of the ozone hole affecting wind.  Now the winds are more similar to what they used to be and warmer ocean temperatures are melting more sea ice.

    The land ice in the Antarctic is most strongly affected by the temperature of the ocean.  As AGW warms the ocean the land ice melts faster where it enters the sea.  This affect is slow to start because the ocean is warmed in the Tropics and then currents slowly move the warm water all the way to the Antarctic.  Currently, especially in West Antarctica, the ocean is warming and melting the great ice sheet.  The warmer ocean does not affect the sea ice as much as the wind did.

    So if you have strong offshore winds the sea ice increases while increasing ocean temperatures melt the ice sheet.  In general, the ice sheet is more important since if it melts hundreds of millions of people will be flooded, including much of Florida and other coastal states.  Sea ice does not affect sea level.

    There are more complications if you look more in depth.  Warmer air causes snowfall to increase.  If snowfall increases enough the East Antarctic ice sheet (which is much bigger than the West Antarctic ice sheet) may increase in size even as the edges melt faster from the warmer ocean.  It is difficult to measure the exact balance of the East Ice sheet because it is so remote and cold and big.  An error of a few centimeters per year would be significant. 

    Wunderground (weather blog) has had a series of blogs on measuring the snowfall in East Antarctic here is the last one.  Currently it is believed that the East Ice Sheet is very slowly losing mass but that could change (either up or down) depending on how much CO2 is eventually emitted.

  50. How can land ice be decreasing, while sea ice is increasing at the same time?


    [PS] Several commentators have already answered. See above.

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