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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)

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.

Last updated on 10 July 2013 by mattking. View Archives

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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

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Comments 51 to 100 out of 318:

  1. cjshaker - Sorry, missed replying to part of your post.

    You asked: "If the ice cores were taken from ice on water, the inverse temperature relationship should still hold?"

    See Figure 3a at the top of this page. The inverse temperature relationship does not currently hold.
  2. During a glacial warming phase, like we're still in now, shouldn't it be getting warmer everywhere?

    It seems to be hard to find accurate information about the ice age cycle, but I assume that this National Geographic article should be fairly accurate. It claims that we reached temperatures 4.5C warmer than today during the previous warm phase. If that is true, why would we not reach similar temperatures during this warm phase, with or without man's CO2?

    http://news.nationalgeographic.com/news/2007/07/070705-antarctica-ice.html

    Chris Shaker
  3. Oh, sorry, I already asked that question...
    Chris Shaker
  4. It was interesting to learn about the GRACE satellite, the shrinking land ice mass, and the growing sea ice mass.

    Thank you,
    Chris Shaker
  5. For interested parties, a recovered copy of Tamino's post Sea Ice, North and South, Then and Now (from the Further Reading section at the end of the post above) is available here.

    The Yooper
  6. Chris Shaker @ 53 It claims that we reached temperatures 4.5C warmer than today during the previous warm phase. If that is true, why would we not reach similar temperatures during this warm phase, with or without man's CO2?

    Because the orbital and rotational parameters of this interglacial are different from the last, the Eemian. Changes in the Earth's orbit (less eccentricity, greater perihelion distance) and rotation (lower obliquity & precession) mean the Earth won't heat up as much during this interglacial from solar radiation.

    Relying only on Milankovitch cycle forcing, the Earth should be cooling:

    Variations in the Earth's Orbit: Pacemaker of the Ice Ages

    "A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next several thousand years is toward extensive Northern Hemisphere glaciation."
  7. Please comment on the accuracy of the following.

    The following statements appear to be correct.

    1. Atmospheric heat, worldwide, has been steadily increasing from year to year for the past two decades.
    2. Worldwide, the total volume of earth's ice has been in decline for the past two decades.
    3. The cause appears to be the increased greenhouse effect as levels of atmospheric CO2 grew from 280ppm in the 1950's to the current level of 390ppm in 2010.
    4. Estimates for the residence time of anthropogenic CO2 in the atmosphere range from a low of 1000 years to estimates as high as 100,000 years.

    If the foregoing statements are accurate is it also accurate to conclude their signifigance as?

    1. Any program designed to reduce our future global carbon footprint can have no effect on slowing or reducing the advance of climate change until the minimum residence lifetime of the anthropogenic CO2 already aloft (390ppm)is achieved or some currently undeveloped geoengineering response is able to remove anthropogenic CO2 from the atmosphere to one or more of the other compartments of the carbon cycle.

    2. The melting of ice worldwide will continue, uninterrupted, until all of the ice is melted if the time it will take to melt it all is less than the minimum anticipated residence lifetime of current levels of anthropogenic CO2 already aloft (1,000 years).

    3. The increase in levels of atmospheric temperature to be expected from an ice free planet are almost certain to exceed human capacity to survive.
  8. albertsonrich
    I presume your numbers come from David Archer's estimates or something similar. There are several diffferent processes at play and only a fraction of what we emit will stay in the atmosphere that long.
  9. Re: albertsonrich (58)

    This isn't really the proper thread for your questions, but as they span multiple potential threads I'll attempt a brief answer of each point.

    If you're looking for a more in-depth answer with source references, use the search function in the upper left of each page to search for the most appropriate thread for any questions you may still have.

    Assuming (we both know what that makes us) you wish a cut-to-the-chase, give-me-a-straight-answer to your questions, here goes:

    1. No real easy answer to this one, as what is tracked is energy, typically in the form of Watts/square meter or temperature in the form of anomalies or ocean heat content in joules. Due to the GHG effects of CO2, yes, energy is accumulating in the system (about 93% in the oceans, the remainder in the air).

    2. Yes (land ice in the form of alpine glaciers and continental ice sheets and sea ice in the Arctic are all in net decline).

    3. Most will shy from giving you a solid answer to this one. It is not 100% certain, but overall, I think that you have the right of it; caveated that 100% attribution cannot be made.



    4. Complex question. Unlike other GHG's, CO2 has a long residence time (a long "tail"). Full sequestration involves chemical weathering processes taking thousands of years. Assuming that humans cease playing the "pile it on" game...(cue next question)

    ***********************************************
    1. As long as human-derived CO2 emissions are greater than zero, in the absence of some CCS program, the atmosphere will still be out of radiative balance. Once net emissions = zero, approximately 30-50 years must elapse before radiative balance will be achieved (mostly due to thermal lag of the oceans and subsequent smaller feedbacks). Dwell for a moment on the thought that we are just now experiencing the effects of the carbon slug injected during the 70s...

    2. No. Much too simplistic of a question. There appears to exist tipping points for Arctic sea ice, the Greenland Ice Sheet and the West Antarctica Ice Sheet (Hansen 2008, I think). Given that the last time CO2 concentrations were this high, global temps were some 3 degrees C higher and sea levels some 6-12 meters higher. Given the residence time of CO2 in the atmosphere, we're faced with the loss of summer sea ice in the Arctic (a 2010 study indicates that the system supports only a full-ice or a no-ice solution for the Arctic; i.e., once summer ice is lost, the system proceeds to a no-ice solution within as little as 6-10 years, depending on the model run). Given that, we must resign ourselves to the eventual loss of the GIS and the WAIS sometime within the next millenia (Hansen's study indicates 5+ meter sea level rises per decade by 2100 is a possibility due to ice melt and outlet glacier calving).

    3. Unknown. If we continue BAU for another 20 years, the probability of an Arctic methane clathrate/hydrate release goes from its already non-zero status to perhaps an eventually likelihood. If we "burn it all", including the shale sands fossil fuels, Hansen maintains we can't rule out a runaway GHG "Venus Effect" or a hydrogen sulfide release such as seems to have occurred during the PETM. This is an area fraught with uncertainty, so your guess is as good as mine here. My thought is that the temperature increases and sea level increases will be the least of our worries (Google evapotranspiration decreases, soil aridity increase; an upcoming study proposes 70% of today's arable soils will be too dry to support crops by 2052...).

    Understand this: a synopsis-type answer such as I have given you in answer to your questions must necessarily be reflective more of my opinion of the consensus of understanding of the field than a considered opinion by the academic societies, the IPCC or even skeptical Science.

    Any further questions, please search for the most appropriate thread and post there. Thanks!

    The Yooper
  10. Expalain this.
    Is there a pattern?
    http://en.wikipedia.org/wiki/File:Vostok_420ky_4curves_insolation.jpg
    Response: [Daniel Bailey] Do you see a pattern? Please elaborate more on what your question is, as I don't have enough specifics to go by. Thanks!
  11. Well i see one....does anybody else?
    I see ca.130,000 years ago the same CO2 levels like today, again 230,000 the same levels and 330,000 higher than today.
    If this was someone's ,say..., bloodpressure chart, i would say this person has elevated bloodpressure every 100,000 years (lol)
    Its safe to say that if we erase the text from the graph and show it to anyone, everyone would see the pattern.
    But one question stands and no one can answer....
    Ok, humans drive our climate today with CO2 emissions, who was the driver 130,000 years ago and the exact same driver 230,000 years ago and did it again 330,000 years ago?
    thank you for your time....
    Response: [Daniel Bailey] You are very much incorrect about the same CO2 levels as today existing in the timeframes you mention. The graph you refer to had a zero year baseline of 1950, when CO2 levels were much lower than today. See the updated graph I posted in comment 60 above. As for the blood pressure reference, Muoncounter nailed it in Comment 63 below. In fact, see the links Muoncounter cites for the appropriate answers to the rest of your questions. Thanks!
  12. #62: Have a look at Climate's changed before, Correlation between CO2 and temperature and CO2 is not the only driver.

    "If this was someone's ,say..., bloodpressure chart,"

    Interesting analogy. In those terms, today's records would be the chart of a person who is being given CPR by a hyperactive teenager or perhaps the Incredible Hulk.

    Please note this thread is about current Antarctic ice loss. One of the links above is a more appropriate place for the 'driver' question.
  13. The question stands (still...).
    130000 years ago CO2 levels = 1950
    230000 years ago CO2 levels = 1950
    330000 years ago CO2 levels = 1950
    If we are raising CO2 levels today who did 1/4 of a million years ago? Thats all i m asking

    PS
    muoncounter since the ice cores and data are from Vostok Antarctica research station and if the ice there is melting away lets pay the last tribute to the station, (perhaps they will drill for soil cores in few years) and write here... hope thats ok with u
    Response: [Daniel Bailey] Ask a question, get an answer. If you want to be taken seriously, when you do get an answer and it contains linked references for you to read as homework it is then incumbent upon you to do that homework. Muoncounter was kind enough to give you some linked references for your gaining an understanding of the subject of your question. Please read them & ask questions on those threads if you have questions therein. Also please read this link as well. Thanks!
  14. Today is not 1950, it is 2011. The CO2 levels are higher now than they've been in the whole record of the Vostok ice cores. To say otherwise is denial, plain and simple. To talk about 1950 levels in a discussion concerning today is nothing but misdirection.

    The spikes were caused by net oceanic outgassing in response to increased solar irradiance from the Milankovitch cycles (orbital variation). The oceans and terrestrial biomes are currently net sinks. The primary source references to validate this claim are available elsewhere on this site. Please post any questions and responses on this matter under those entries.
  15. So..... 1950 levels are equal to 1/4 of a million years ago with no industrial revolution....
    Thanks for answering my question by spending your precious time.

    Good Night, and Good Luck

    PS
    Im not in denial.... maybe u are. I did spend 40000 € 4 years ago for solar panels on my roof (did u?)to produce clean, CO2 free electric power and i m cleaning now the snow of almost on a daily basis.... so spare me the "denial" article
  16. Vank - So..... 1950 levels are equal to 1/4 of a million years ago with no industrial revolution..

    See my comment @ 57. It's Milankovitch cycles. The previous interglacial cycles were warmer because the timing/variation of Earth's orbit/tilt/wobbles lead to greater solar radiation at the surface (insolation).

    No such confluence of factors exist during this interglacial. In fact we have already seen the natural high point of this interglacial during the Holocene Climatic Optimum, about 6000 years ago. The warming we are experiencing now is not natural, in fact we should be on our way to "extensive Northern Hemisphere glaciation".

    Variations in the Earth's Orbit - Pacemaker of the Ice Ages

    Hope this helps clear this up for you. Also: sorry to hear about your solar panels, but even decades from now, when it's globally much, much warmer, there will still be snow in winter.
  17. @vank #66

    There are now at least two antipodal points in the Earth with the same temperature and pressure. That's absolutely true. And?

    Say whatever you want, and I will tell you there still are two antipodal points ...

    It makes no sense? Why? You were making the same kind of argumentation with your 1950/minusquartermillion reference.

    Let me rephrase your idea "in 1950 C02 levels were the same as in 234116BC without industrial revolution the same way there were no atomic weapons when women had not right to vote" We can safely infer important conclusions from those facts.
  18. This your idea not mine....voting rights and nuclear weapons vs. ice core samples and graphs(interesting argument. The "rephrasing ideas" system is only a sophists trick.
    Its a graph and it tells something or we can all play Struthio camelism.
  19. @vank #69

    Thank you. You have expressed your ideas and background quite clearly.

    The right answer would have been an epistemologically valid argumentation and inference departing from your CO2 similar levels. You were asked that before and avoided to provide it. Now, confronted with your "trick" you abandon all doodles in climate science and answer in a proficient way about "tricks" including what I suppose to be an expression proper of the "trade".

    Keep this coming and thank you again. I need for my students more material like your posts, which are very juicy for that purpose.
  20. OK, there is one point in this article which is puzzling me. Take these two paragraphs:

    "In contrast, the Southern Ocean has been warming at 0.17°C per decade. Not only is the Southern Ocean warming, it is warming faster than the global trend."

    "Another contributor is changes in ocean circulation. The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more stratified and mix less. Less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted."

    So the first paragraph suggests that the sea temperature is increasing, the second that the sea (surface) temperature is decreasing, and that this along with the winds is causing the extra sea ice.

    Does the difference come from the fact that the first measure is sea temp and the second is sea *surface* temp? I don't think so - the 0.17 number looks like a sea surface temp result.

    The second para says the sea surface layer is cooling. Or does it? No, it says less heat enters it from below. Does that make a difference? But surely only cooling would explain more ice? Unless ice formation involves temporary inhomogeneities perhaps? Are there any measurements which show surface cooling?

    No-one has mentioned the change in freezing temperature with salinity, so I presume that is too small to be significant.

    Thanks for any help, Kevin
  21. Any loss of land or sea ice due to melting increases sea levels which threatens those in Florida waterfront real estate. In fact the majority of the state at such a low sea level may be threatened even while more and more people migrate south.
  22. No-one answered my question, so I looked up Zhang 2007. From the abstract:

    "The model shows that an increase in surface
    air temperature and downward longwave radiation results in an increase in the upper-ocean temperature
    and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979–2004 and the extended period 1948–2004."

    If I understand that, the air is warming the water leading to less freezing. However, once frozen, the ice insulates the water below, and the decrease salinity prevents convection from below bringing heat to melt it, so melting is also reduced. The reduction in melting is greater than the reduction in freezing, and so there is more ice.
  23. I've got a query, or two.

    The surface temperature over the past decade has been mostly steady and yet we attribute significant ice trends to the warming climate. Well over the past century we recorded significant unprecented global warming, so shouldn't the polar regions also have undergone significant observable change in that time? Is there evidence of that? (extrapolate those charts back another 100 years over a period when it actually warmed)

    I don't see how we can attribute polar ice trends to climate change when the climate isn't changing but ignore the much longer period when it changed a lot. The poles must be significantly different places now to what they were in 1900 if the period 2000-2010 is considered significant when climate change took a breather.

    (Yes we're limited by the fact that the polar regions haven't always been accessible, but scientists have their ways)

    Or on the same track we might ask why people are using 10 year (and less!) observation periods to glean affects of global warming at the poles and yet we would never use such periods for land observations because they're too short.
  24. OK lets substitute lower atmoshphere for surface temperature, that's what the satellite measures

    http://www.drroyspencer.com/wp-content/uploads/UAH_LT_1979_thru_Mar_2011.gif

    Is that an acceptable source DSL?

    Can we address the main points made which this isn't?
  25. Doesn't work, Ryan. You need to look at ocean temps as well when discussing polar changes. The entire basis of your argument is wrong, so this is addressing your main point.

    That's a pretty big jump from the Spencer-interpreted UAH LT "mostly steady" (not really) to "the climate isn't changing." There is overwhelming (as in too many studies to keep track of) evidence that the climate is changing rapidly, whatever the cause. The Arctic sea ice anomaly is nose-diving, and the global glacier mass balance is diving even more sharply.
  26. No that isn't the entire basis of the argument DSL, far from it.

    The point is the article attempts to draw climatic trends from periods of under 10 years.

    Do you think this is an adequate length of time DSL?

    If we take the claims of the article as truth and extrapolate back over the past century of warming do we obtain a result which is backed up by real world observation for that period?

    ("mostly steady", the anomaly today sits where it started 12 years ago, yes mostly steady)
  27. RyanStarr, it should be self-evident that ice trends would only follow temperature trends between the time that the temperature was sufficient to cause ice melt and when it was sufficient to have melted ALL the ice.

    Thus, your insistence that the 'failure' of the Antarctic ice trend to follow the temperature trend over the past 100 years is significant would only be logical if Antarctic ice were melting that entire time... which it wasn't.

    As to: "the anomaly today sits where it started 12 years ago, yes mostly steady"

    By that reasoning we would be forced to conclude from a 55 degree day in February and a 55 degree day in May that the temperature had been "mostly steady" over the intervening three months. Any rational person should know better.
  28. CBD I'm not exactly sure what you're getting at in the first paragraph. Are you eluding to the fact that ice melts or doesn't melt and for all temperatures below 0 the ice will be frozen?

    That's true but we're not dealing with a smooth climate, seasonally the ice expanse at the poles swings wildy. In winter ocean ice is a multiple 5-10 times what it is in summer, as a ball park range.

    So there is and always has been very much melting at the poles and our concern is the mean figures over time.
  29. RyanS#78: "seasonally the ice expanse at the poles swings wildy. In winter ocean ice is a multiple 5-10 times what it is in summer, ... there is and always has been very much melting at the poles"

    If by 'poles,' you're including the Arctic, then you are:
    a). off topic
    b). making an unsubstantiated claim
    c). incorrect.

    Arctic ice extent did not always swing wildly; there are a number of Arctic ice threads with plenty of actual data to examine. If it's credibility you seek, point to some numbers.
  30. We were also talking about LAND ice in Antarctica... not sea ice. Or, at least, that's the only thing I can think of which '10 year trend' might have been referring to.

    Since surface temperatures on most of the continent (peninsula excepted) seldom get above zero, land ice wasn't expected to start declining for decades. Yet it already has because rising ocean temperatures have cleared out sea ice and ice shelves while also undermining coastal land ice... all of which leads to faster ice export and the recently observed continent wide trend of declining ice.
  31. @ 80 "...rising ocean temperatures have cleared out sea ice.."

    Cleared out sea ice in Antartica? You need to read the article above, it attempts to explain why the observed rising sea ice in Antartica can occur in a warming climate.
  32. Muoncounter, we've always had and always will have seasons, climate change isn't changing that. Look at photo above showing March and September extents for both the Arctic and Antarctic.

    Point me to some evidence which shows arctic ice extent used to be a more static quantity than it is now. I recall a picture from the 50s showing a submarine poking through slush at the north pole.
  33. Wow - trotting out the old submarine photo. It's in a polynya!

    For evidence of part arctic sea-ice, see arctic sea ice threads. You can find pointers to the relevant papers on past sea-ice seasonal limits there.
  34. Ryan, try taking arctic comments to arctic sea ice melt is a natural cycle
  35. RyanStarr wrote : "I recall a picture from the 50s showing a submarine poking through slush at the north pole."


    Could you post further details on the thread suggested by scaddenp.
  36. Ryan, the "rising" trend in Antarctic sea ice extent is extremely small and in no way contradicts what I was saying. Indeed, breakup of sea ice, collapse of ice shelves, and increased export of land ice into the ocean all cause increased sea ice extent.
  37. Because of errors in Grace data extrapolation, it has been determined that the ice mass on Antarcica is neither shrinking nor growing.

    So, no net change there.
    Response:

    [DB] Umm, you seem to be confused.  Please read the OP and the comments, with particular attention to Ned's comment at 30 above.  If still unsure, try the Intermediate version of this post.  The totality of Antarctica (the Antarctic Peninsula, the WAIS and the EAIS) are all losing mass, beyond that of the error bars.  And the rate of mass-loss is itself increasing.

  38. Given that ice requires 334 joules per gram to melt where do you propose that energy is coming from over the land of antarctica ??

    Do you propose that it coming from the 390 ppm CO2 with its specific heat of less than 1 joule per gram ?

    I havent done the maths on this because it seems unbelievable that it has the capacity to cause warming on the scale it is credited with.
  39. Rosco, see the Intermediate version of this post.

    The land ice on Antarctica does not 'melt' by direct heating from air or insolation so much as it loses the balance it formerly had between gains and losses.

    The losses are (mainly) attributable to the heat now in the oceans, accumulated over the last couple of centuries. The ocean is taking more from the edges than the icecap and glaciers can accumulate at their centre/top.
  40. Rosco, sorry I hit the button too soon.

    Melting. The issue is that much of the ice does not melt in situ. It thins, weakens and breaks off and the ocean transports it away in the form of icebergs.

    These may not melt for quite a long time after they've subtracted their bulk from their source glacier.
  41. The ice is not melted by conductive energy transfer so specific heat is irrelevant. Melting is from radiative energy transfer - ie the energy is the from sun and more of it is trapped because of the CO2. Perhaps you should do the math. What does an extra 1.5W/m2 (global annual average all forcing) give you?

    Also warmer water onlapping Antarctica increases calving which I believe remains the main source of ice loss in the Antarctic.
  42. Following up on posts by Camburn here, the most recent paper on Antarctic Ice Mass Balance I can find is Rignot et al 2011, published in March of this year. It finds:

    "In 2006, the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise. Notably, the acceleration in ice sheet loss over the last 18 years was 21.9 ± 1 Gt/yr2 for Greenland and 14.5 ± 2 Gt/yr2 for Antarctica, for a combined total of 36.3 ± 2 Gt/yr2. This acceleration is 3 times larger than for mountain glaciers and ice caps (12 ± 6 Gt/yr2). If this trend continues, ice sheets will be the dominant contributor to sea level rise in
    the 21st century."


    It does not distinguish between ice lost from West or East Antarctica.

    The most recent article I found that does distinguish between them is a review article by Cazenave and Llovel (2010) which finds the majority of the ice loss on the West Antarctic Ice Sheet, with East Antarctica being found to be "in near balance".

    The most recent GRACE data I can find is from Chen et al (2009) which finds:

    "In agreement with an independent earlier assessment, we estimate a total loss of 190 +/-77 Gt yr^1, with 132 +/-26 Gt yr^1 coming from West Antarctica. However, in contrast with previous GRACE estimates, our data suggest that East Antarctica is losing mass, mostly in coastal regions, at a rate of 57 +/-52 Gt yr^1, apparently caused by increased ice
    loss since the year 2006."


    This evidence clearly supports the view that ice loss from West Antarctica significantly excedes that from East Antarctica, but is ambiguous about whether East Antarctica is loosing ice. On balance, it is probably loosing ice, but the GRACE experiment may well be overestimating the rate of loss.
  43. There's a nice article over at weather underground explaining the Zhang paper in more comprehensible terms. With pictures. It's here:
    http://www.wunderground.com/blog/RickyRood/comment.html?entrynum=194
  44. http://www.agu.org/pubs/crossref/2011/2011GL047553.shtml
    doi:10.1029/2011GL047553
    Sudden increase in Antarctic sea ice: Fact or artifact?

    Three highly-cited data sets depict a sudden large increase in Antarctic sea ice
    This step-change is fake and is related to a switch in source data
    Recent sea ice trends are significantly exagerated becuase of this data problem

    (typos in the original)
    http://www.agu.org/pubs/crossref/2011/2011GL047553.shtml
    Response: [Dikran Marsupial] Links activated
  45. While I'm very wary of drawing any conclusion from a single paper (an error which this article suffers from particularly, in my opinion), the following paper adds another piece to the puzzle. (Whether it is in the right place is another question.)
    http://www.aoml.noaa.gov/phod/docs/Shu_etal_2011.pdf

    (via Ari at AGW observer)
  46. While I'm very wary of drawing any conclusion from a single paper (an error which this article suffers from particularly, in my opinion), the following paper adds another piece to the puzzle. (Whether it is in the right place is another question. Given that they claim an increasing sea ice trend, when the trend itself is barely significant, I have reservations about the statistics.)
    http://www.aoml.noaa.gov/phod/docs/Shu_etal_2011.pdf

    (via Ari at AGW observer)
  47. News yesterday: NASA finishes the first Antarctic ice flow speed map.
  48. I was recently quoted Ian Joughin and Slawek Tulaczyk 2002 as proof that WAIS is gaining ice. In the article I read that the sheet is marine based, but grounded, so does that count as land ice? Also, the the third to the last paragraph the article indicates that it is only about the Ross ice streams: “This analysis covers only the Ross Sea sector of the ice sheet, and negative imbalances are observed in other areas of West Antarctica such as Pine Island and Thwaites Glaciers.” Is that why there isn't any conflict between that article's gaining ice conclusion and the GRACE 2002-2009 data showing land ice loss?
    Response:

    [DB] The WAIS is in negative mass-balance.  While the interior of the EAIS is gaining mass, its edges are losing mass sufficient to put the EAIS overall into negative mass-balance.  Now that negative could be as little as 5 Gt/yr or as much as 67 Gt/yr (IIRC).

    Antarctic sea ice is gaining some in the metrics of area and extent, but this is an expected response to increased precipitation to the warming of its circumpolar current.

    The PIG and Thwaites are the linch-pin to the WAIS; without their stabilizing presence, ice flow rates will accelerate greatly.

  49. I understand that both WAIS and EAIS are in negative balance. I am trying to reconcile that knowledge with the paper linked above. The abstract states "We have used ice-flow velocity measurements from synthetic aperture radar to reassess the mass balance of the Ross Ice Streams, West Antarctica. We find strong evidence for ice-sheet growth (+26.8 gigatons per year), in contrast to earlier estimates indicating a mass deficit (−20.9 gigatons per year). Average thickening is equal to ∼25% of the accumulation rate, with most of this growth occurring on Ice Stream C. Whillans Ice Stream, which was thought to have a significantly negative mass balance, is close to balance, reflecting its continuing slowdown. The overall positive mass balance may signal an end to the Holocene retreat of these ice streams."
    Does the +26.8 Gt apply to only the Ross Ice Streams and not to WAIS as a whole?
    Response:

    [DB] It's good that you question the 2002 study (as that is the skeptical thing to do).  Joughlin does absolutely splendid work and is highly regarded in the field.  From Ian Joughin and Slawek Tulaczyk 2002 (3rd to last paragraph in the paper):

    This analysis covers only the Ross Sea sector of the ice sheet, and negative imbalances are observed in other areas of West Antarctica such as Pine Island and Thwaites Glaciers.

    Emphasis added, obviously.

    Anyone who tries to extrapolate this result, especially in lieu of later, continental scale findings like detailed in the OP above or the Intermediate version of this post, is a serious Cherry-Picker.

    I would also encourage you to review Rignot's latest work, discussed here.  Absolutely fascinating stuff.

    Note:  Science allows individuals to register for free downloads of the older material, such as the study Joughlin study referenced in this comment.  The cherry-pickers and dissemblers of the world count on people not fact-checking their claims. 

    Don't let them win.

  50. SocialBlunder,
    Have you looked at the intermediate tab? From that article, the 2002 paper might not be in error (since the data was probably obtained sometime before 2002). The 2nd figure (from Velicogna 2009) shows a curve that indicates that somewhere around 2001 or 2002 the ice mass was stable. Now the ice mass is negative and the loss is increasing by ~26 Gt/year. So if that acceleration is constant and if the ice sheet was in balance in ~2002, then in ~2001 the ice sheet would have been gaining 26 Gt/year. A lot of ifs there, but I see no reason to disbelieve the 2002 paper and don't see it contradicting this article - it's just that the 2002 uses outdated information (not their fault - it was current when they printed it).

    But take that with a grain of salt. IANACS (I am not a climate scientist), just an aerospace engineer living as a computer scientist :).

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