Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
Keep me logged in
New? Register here
Forgot your password?

Latest Posts

Archives

Climate Hustle

Is Antarctica losing or gaining ice?

What the science says...

Select a level... Basic Intermediate

Satellites measure Antarctica is gaining sea ice but 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)

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. While their results for the Antarctic Peninsula and much of West Antarctica agree with other research, the study disagrees with many other techniques. We will update this discussion once more studies address this issue. Until then here are links to some recently published takes on the study:

A controversial NASA study says Antarctica is gaining ice. Here’s why you should be skeptical - Chris Mooney (Nov. 5)

NASA Scientist Warned Deniers Would Distort His Antarctic Ice Study — That's Exactly What They Did - Media Matters (Nov.4)

More on Antarctic Ice Melt - ClimateCrocks (Nov. 3)

Is Antarctica Gaining or Losing Ice? Hint: Losing. - Phil Plait (Nov. 3)

Q&A: Is Antarctica gaining or losing ice? - Carbon Brief (Nov. 3)

Just Because Antarctica Might Be Gaining Ice Doesn't Mean Climate Change Isn't Happening - Vice (Nov. 2)

Skeptic arguments that Antarctica is gaining ice frequently hinge on an error of omission, namely ignoring the difference between land ice and sea ice.

In glaciology and particularly with respect to Antarctic ice, not all things are created equal. Let us consider the following differences. Antarctic land ice is the ice which has accumulated over thousands of years on the Antarctica landmass itself through snowfall. This land ice therefore is actually stored ocean water that once fell as precipitation. Sea ice in Antarctica is quite different as it is ice which forms in salt water primarily during the winter months. When land ice melts and flows into the oceans global sea levels rise on average; when sea ice melts sea levels do not change measurably.

In Antarctica, sea ice grows quite extensively during winter but nearly completely melts away during the summer (Figure 1). That is where the important difference between Antarctic and Arctic sea ice exists as much of the Arctic's sea ice lasts all the year round. During the winter months it increases and before decreasing during the summer months, but an ice cover does in fact remain in the North which includes quite a bit of ice from previous years (Figure 1). Essentially Arctic sea ice is more important for the earth's energy balance because when it increasingly melts, more sunlight is absorbed by the oceans whereas Antarctic sea ice normally melts each summer leaving the earth's energy balance largely unchanged.

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

One must also be careful how you interpret trends in Antarctic sea ice. Currently this ice is increasing overall and has been for years but is this the smoking gun against climate change? Not quite. Antarctic sea ice is gaining because of many different reasons but the most accepted recent explanations are listed below:

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).

and

ii) 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.

All the sea ice talk aside, it is quite clear that really when it comes to Antarctic ice and sea levels, sea ice is not the most important thing to measure. In Antarctica, the largest and most important ice mass is the land ice of the West Antarctic and East Antarctic ice sheets.

Therefore, how is Antarctic land ice doing?

Shepherd et al. 2012
Figure 2: Estimates of total Antarctic land ice changes and approximate sea level contributions using a combination of different measurement techniques (Shepherd, 2012). Shaded areas represent the estimate uncertainty (1-sigma).

Estimates of recent changes in Antarctic land ice (Figure 2, bottom panel) show an increasing contribution to sea level with time, although not as fast a rate or acceleration as Greenland. Between 1992 and 2011, the Antarctic Ice Sheets overall lost 1350 giga-tonnes (Gt) or 1,350,000,000,000 tonnes into the oceans, at an average rate of 70 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 0.19 mm/yr.

There is variation between regions within Antarctica (Figure 2, top panel), with the West Antarctic Ice Sheet and the Antarctic Peninsula Ice Sheet losing ice mass, and with an increasing rate. The East Antarctic Ice Sheet is growing slightly over this period but not enough to offset the other losses.  There are of course uncertainties in the estimation methods but independent data from multiple measurement techniques (explained here) all show the same thing, Antarctica is losing land ice as a whole, and these losses are accelerating quickly.

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 8 November 2015 by BaerbelW . View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

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.

Update

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.

Comments

Prev  1  2  3  4  5  6  7  8  9  10  

Comments 451 to 463 out of 463:

  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.  


    http://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses

  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.”


    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

  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:

    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).

  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, nsidc.org?

  14. 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?

Prev  1  2  3  4  5  6  7  8  9  10  

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page



Get It Here or via iBooks.


The Consensus Project Website

TEXTBOOK

THE ESCALATOR

(free to republish)

THE DEBUNKING HANDBOOK

BOOK NOW AVAILABLE

The Scientific Guide to
Global Warming Skepticism

Smartphone Apps

iPhone
Android
Nokia

© Copyright 2017 John Cook
Home | Links | Translations | About Us | Contact Us