A Few Things Ill Considered

A layman's take on the science of Global Warming featuring a guide on How to Talk to a Climate Sceptic.

Wednesday, March 22, 2006

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The Ice Caps Will Melt Into the Aquifers

(Part of the How to Talk to a Climate Sceptic guide)

Objection:
Even if the ice caps melt, the sea level won't rise that much because the melt water will be absorbed in the aquifers underneath.

What can I say?.

Answer:
This is a ridiculous notion, both for making the assumption that no glaciologist or ice sheet expert or climatologist in general could not have thought of it themselves and for getting it so wrong that a minute adding up numbers could have saved some embarassment.

97% of the world's water is ocean, let's ignore it. 68.7% of the remaining fresh water is locked up in glaciers and ice caps, the vast majority in ice caps. 30% is currently groundwater. (See here.)

The total area of land on earth is about 148.3 million sq km. The antarctic is about 14 million, Greenland 2.2 million. So the portion of land under ice sheets is around 11% (easily googled)

So in short, for this theory (cough) to work we need one tenth of the land area on earth to absorb twice as much water as has been absorbed by all the other nine tenths together. It somehow does not seem to pass the sniff test.

Those calculation further assume that there is no ground water there already, which I don't know but I really doubt it. The bottom of the antarctic ice is only a couple of degrees below freezing due to geothermal heat and the insulating effect of thousands of metres of ice. Why wouldn't there be liquid water in the ground (which is bedrock btw)? And if it is too cold, why wouldn't any aquifers already be full of frozen water?

No, this theory is no Copernican Revolution, we should accept the calculations and warnings of the experts. If the greenland icesheet melts completely it will add ~7 metres, WAIS will add about 8 (it is already mostly below sealevel) the EAIS would add around 65m (see here)

Not that they will all melt anytime soon.

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30 Comments:

  • At March 26, 2006 9:42 AM, Blogger ezm1 said…

    "So in short, for this theory (cough) to work we need one tenth of the land area on earth to absorb twice as much water as has been absorbed by all the other nine tenths together. It somehow does not seem to pass the sniff test."

    I tend to agree with you but you failed to dynamic element to H20 in the form of evaporation/precipitation. The wather isn't all necessarily going to remain exactly were it melts. More water on the surface will lead to more water in the atmosphere and thus more rain on land (which could supply underground sources, which in many cases are depleted)

    --Mike

     
  • At March 26, 2006 10:21 AM, Blogger coby said…

    I don't think it is true in any practical sense that more surface water means more atmospheric moisture. 70% of the earth's surface is already water, not counting rivers, swamps and lakes. The amount of vapor in the air is by and large a function of the air's temperature, simply because water is so abundant.

    As for recharging aquifers, that is an interesting factor to think about, I don't have any numbers on that. Of course, most of the depletion is due to humans pumping it out and I suppose we would need to stop that before any higher rainfall might start to recharge things.

    I did listen to an interesting discussion on an NPR podcast with Fred Pearce about the world's water situation. He mentioned how India is relying alot on pumping "fossil water" that has been deep underground for 10K+ years and can not be replenished for many thousands of years. I don't know what the timeframe is for replenishing some of the US aquifers that have been lowering over the decades.

     
  • At May 24, 2006 6:28 AM, Anonymous Anonymous said…

    I have a question regarding this, as I am on the fence right now. Their is concern regarding the melting of polar ice, and the effect it will have on increasing sea levels. What I cannot understand however, is this; Frozen ice occupies a greater volume than the water it contains. So for example, if you half fill a bucket with water, then fill it to the top with ice, and then allow all the ice to melt, the level in the bucket will drop. This I learned from basic unversity physical chemistry, so if the arctic ice melts, surely the sea levels would actually fall as a consequence. I've asked several people this, and most have no answer. Can you explain how melting sea ice will cause sea levels to rise?

     
  • At May 24, 2006 8:14 AM, Blogger coby said…

    You are quite correct that floating sea ice is already displacing the volume of water it would turn itno if it melted, so no one should be telling you that sea level will rise from melting sea ice. FWIW, I have heard this concern before, but never seen anywhere remotely reputable where this claim about sea level rise was made.

    When you see people refer to polar ice melt raising SL, they should be referring to the East and West Antarctic ice sheets and the Greenland ice sheet, with 65, 8 and 6-7m SLE (sea level equivalent) respectively.

    There is an indirect way that the loss of arctic sea ice can cause SL rise, and that is due to the much darker surface of open water than ice. This means the water will absorb more direct sunlight and warm. Warming water causes thermal expansion.

    In the IPCC TAR report it says that most of the observed 20th and projected 21st centruy SLR is due to thermal expansion.

     
  • At August 18, 2006 1:22 PM, Anonymous Anonymous said…

    Floating polar ice will not increase the level of the oceans if melted. It also won't "decrease" the level of the ocean as someone postulated. It will have a net zero volume change. Which is the case for the Arctic Ice Cap. The Arctic Ice Cap is a floating, moving mass of ice.

    However, the Antarctic Polar Ice cap is primarily located over a land mass. As this ice is not "floating," if it melts it will indeed increase the level of the ocean. As will the Arctic Ice in the form of glaciers (such as all the ice on Greenland).

     
  • At September 11, 2006 6:55 PM, Anonymous Anonymous said…

    Yes, the Antarctic ice cap is primarily located over a land mass, but less than half of that mass it is above sea level, and the parts of ice that are not above land over sea level only partly add to rising sea levels after the ice melts.

    It has already been discussed that if you took a pool with water with a large chunk of floating ice, the water level would not rise if the ice melted. And we all agree that if we put a block of ice on the side of the pool and let it melt, the water level would rise if we let the melted ice to drain to the pool. But if we added a large block of ice that was too large to float on the pool (that is, so large that it would touch the bottom of the pool and rest part of its weight on it) the results would be in between: after melting the water level would rise but not as much as if the block of ice started completely above the original water level. This is due to the fact that the original ice occupies less volume than the water it melts into, so only the parts of ice that would be above the original level if the block wasn't touching the bottom do not add to the water level rising.

    I don't know how much below the sea level are the solid surfaces below the Antarctica, and based on available maps it seems to be considerable depth at some parts, much shallower in others. But it would be certainly a significant factor that would reduce the effect of melting ice caps. I'm not saying the specialist missed this point, I'm truly confident in their analysis. What I'm claiming is that this is a point you missed in your analysis as posted so your numbers are significantly off as they depend largely on Antarctic ice.
    On the other hand, the original question does not necessarily imply that the melted ice would be absorbed by the ground below it. Any landmass between current sea level and the sea level after water melting would be absorbing water and that could have a significant effect in reducing the magnitude of any rise caused by ice cap melting. As per your calculations land mass is about ten times larger than ice caps (and if you consider my previous point, it should be even more so), so if ground currently above sea level had a capacity to absorb just 10% of its volume in water any potential raise would be halved, and I think that's the point in the theory.

     
  • At September 11, 2006 8:23 PM, Blogger coby said…

    You're correct I did not factor out that portion of the Antarctic that is below sea level. But this only makes the numbers more convincing.

    I think it is pretty far fetched to think that any significant volume of water would be absorbed by the newly submerged ground. 70% of the current surface is ocean. Of the 30% land surface now, how much will be submerged? I would guess less than 1%. How much water would that store? Don't forget coastal land already has a high water table in general.

     
  • At November 26, 2006 11:26 AM, Anonymous Anonymous said…

    I think that the Ice caps are melting due to salt compounds found in the atmosphere. Just like we put salt on the road. I also think there will be no flood. Even with the large amounts of melting caps, our ocean levels have not climbed. The water is simply evaporating/.If you can find evidence of an increase in water levels, please let me know.

     
  • At November 26, 2006 11:27 AM, Anonymous Anonymous said…

    I think that the Ice caps are melting due to salt compounds found in the atmosphere. Just like we put salt on the road. I also think there will be no flood. Even with the large amounts of melting caps, our ocean levels have not climbed. The water is simply evaporating/.If you can find evidence of an increase in water levels, please let me know.

     
  • At December 07, 2006 4:54 PM, Blogger coby said…

    Please see here for a graph of sea level rise. As for evaporation, if the ir could hold that much more water it would already be doing so, it is abundant on the planet, an ice sheet melting will not alter the physics determining relative humidity.

     
  • At February 02, 2007 12:57 AM, Anonymous Anonymous said…

    One point which Id really like clarity on. The temperature in antartica must be up to 60 below.So before the ice can melt , surely the air temp would have to rise about 60 degrees. And if this were the case, then the last thing humans would need to worry about would be rising oceans as we'd all be dead from heat exposure long before the ice could even begin to melt???

     
  • At February 02, 2007 11:32 AM, Blogger coby said…

    (NB: I am not saying the antarctic ice sheets are melting, this is a general observation)

    There are other ways glaciers and icesheets can shrink besides actually melting into liquid water. Sublimation directly into dry air and flowing into the ocean come to mind. The amount of ice in a given mass represents the balance of snowfall, runoff, calving etc. So even absent any temperature change the cessation of snowfall would eventually eliminate the ice mass. In the case of antarctica, it has been observed to be thickening in the middle because of increased snowfall. This is a situation where a slight warming can cause more ice not less.

    But in general, yes, it is very very cold down there I would expect that ice (East sheet at least) will be there for 10's of thousands of years no matter what. That could still be a very abrupt end for 40 million years of ice cap, geologically speaking.

     
  • At February 20, 2007 2:52 AM, Anonymous Anonymous said…

    "The bottom of the antarctic ice is only a couple of degrees below freezing due to geothermal heat and the insulating effect of thousands of metres of ice. Why wouldn't there be liquid water in the ground (which is bedrock btw)?"

    __________________________

    ...beeecause you just said that the ground was a couple of degrees below freezing, thats why there is no liquid water in the ground.

    I like it when you contradict yourself.

    Does this lead anywhere? Who knows, NOBODY KNOWS! Wohoo!

     
  • At February 20, 2007 12:57 PM, Blogger coby said…

    I said the bottom of the ice was only a couple of degrees above freezing. It only gets warmer as you go deeper underground.

     
  • At February 20, 2007 5:56 PM, Anonymous Anonymous said…

    I said the bottom of the ice was only a couple of degrees above freezing. It only gets warmer as you go deeper underground.

    _______________________________

    A) No you didn't.

    B) Lying from you aside, ever hear a thing called "Permafrost"? But in your own little world, there is no "Permafrost" because it doesn't fit into the current political debate at hand.

     
  • At March 03, 2007 10:22 AM, Anonymous Chris said…

    Hey guys , sorry to butt in here but I had an idea popped into my head just now and figured what the heck!!Lets assume that ALL the ice at the north and south poles has melted and been distributed into the oceans . What would the effect on the spin (and ultimately the trajectory) of the earth be, if billions of tons(?) of ice are no longer situated at the extreme ends of the earth ? Im thinking of a spinning top here and then I think of its centre of gravity being altered and Im going ' Oh no!!! Not something else to worry about!!' Please tell me im being paranoid!!!

     
  • At March 04, 2007 2:32 PM, Blogger coby said…

    Hi Chris,

    I wouldn't worry if I were you. I thin there would be a detectable effect on the rotation for the resons you describe, but it would be very insignificant. Don't forget that there have been times in the earth's past where there was no ice anywhere on the planet but the orbit has not gone haywire!

    FWIW, even the shifting of the ocean bottom that occured during the Asian Tsuami causing earthquake effected the earth's rotation, but again such tiny changes.

    Thanks for the comment!

     
  • At April 12, 2007 11:43 AM, Anonymous Chris said…

    What are your ideas,if any, that man has little or nothing to do with global warming? But that the major cause is due to the sun.I have been reading in a variety of places that all of the planets in our solar system are currently experiencing an increase in warming that , it is speculated , is due to sunspots -or whatever. I have also recently watched a 'documentary' called "The Great Global Warming Swindle" that really got me thinking that there are other reasons than our comparatively meagre CO2 emissions that are causing the rise in temperature currently being experienced.

     
  • At April 12, 2007 4:49 PM, Blogger coby said…

    Hi Chris,

    I think The Great Global Warming Swidle is actually self describing in its title. There really are alot of problems both with its approach and the scientific claims it presents. Have a read here for what working climatologists think about it,
    http://www.realclimate.org/index.php/archives/2007/03/swindled/

    The issue of attribution of current climate change (ie is it anthropogenic or other causes) has been, and continues to be, quite extensively studied and there is currently no comprehensive theory that can explain all the observations we have without the large effect that CO2 concentrations are, in fact, expected to have. The sun has only been very carefully monitored since the satellite era, but over these last three decades it has not varied aside from the 11yr cycle, so it is difficult to imagine how it could be causing such rapid warming.

    Have a read here for a bit more solar detail:
    http://illconsidered.blogspot.com/2006/04/its-sun-stupid.html

    About warming on other solar system bodies, have a look at the material I cited in this recent post:
    http://illconsidered.blogspot.com/2007/04/hot-times-in-solar-system.html

    I don't think it is very accurate to call our emissions "meagre", many things in nature have great effects in small concentrations and the perturbation we have already caused is nothing short of huge. Have a look at this graph of CO2 over the last 450Kyrs:
    http://www.globalwarmingart.com/wiki/Image:Carbon_Dioxide_400kyr_Rev_png

    We have gone off the chart in a geological instant.

    Thanks for the thoughtful questions!

     
  • At May 23, 2007 4:21 AM, Anonymous Anonymous said…

    What about the release of weight on the land masses below the ice? Anyone in Europe can go out and find raised beaches in areas uncovered by the melting of the last ice-age. The effective sea-level is actually 80+ft lower than it was when the ice was in place!! Remember that the land mas below is not a fixed position and is just a crust floating on the magma below. When the overburden of ice melts, the land mass uplifts i.e. relative sea-levels fall and there is more land exposed to absorb the water table.

     
  • At May 23, 2007 12:27 PM, Blogger coby said…

    That is called isostatic reboun and is very important in determining local sea level histories and projections. Isuppose it would be a factor in calculations related to this post but hardly changes the big picture.

     
  • At September 04, 2007 3:20 PM, Anonymous Anonymous said…

    Why use "anytime soon" when "soon" says it?

     
  • At September 04, 2007 3:26 PM, Blogger coby said…

    I'm sorry, I don't understand. Who says "soon"? Besides, the last sentence is my own, no attempt to paraphrase anyone in particular. Also, what is the significant difference between "soon" and "anytime soon"?

     
  • At October 04, 2007 12:06 PM, Blogger Ryan Robison said…

    I am learning more about the ice caps and I have googled my thought on how to save the ice caps and have found nothing. I know that we all need to kick the carbon habit and clean our environment up. From what I have seen that is definetly not going to stop the ice caps from melting. Only slow it down. So what if in the mean time we use a band aid and drill holes in the ice caps then insert what I call big freezer tubes to keep it from melting so fast now while we cut our carbon emissions and clear up our air. I am assuming that it has been thought of but money is probably a factor. Don't forget greed. There is land and oil under there you know. I hope we can do something and do it soon.

     
  • At October 24, 2007 11:08 AM, Anonymous Anonymous said…

    The thing I have learned about global warming "scientists" is that if anyone disagrees with them they get angry, as if they are infallible. They are so arrogant that they think the temperature right now is the optimal temperature that the Earth should be at and that humans are responsible for the increase in temperature. Well "scientists" similar rises in temperatures are being reported on Saturn are we responsible for that. Who was responsible for the last ice age. I will give you a hint, the same person that is responsible for the higher temperatures mother nature.

     
  • At November 01, 2007 2:01 PM, Anonymous Bruce said…

    I agree with anonymous above me. There's really nothing we're gonna do about "global climate", as its called now, simply because we're not a cause of it. There have been ice ages and warm periods more extreme then we're at right now and I'm pretty sure people didn't have any carbon emissions or anything else back then. Unless it was the dinosaurs. That would explain why they're extinct. They didn't care for their environment enough.

     
  • At January 22, 2008 4:53 PM, Anonymous Anonymous said…

    hi coby good blog but i have a few questions that i dont think you answered in the faqs section. Firstly tho i would like to say i am not a sceptic or a strong follower of climate change i would just like to know more of the facts behind it.

    question 1) even if all the ice at say the north pole melts there will be no net change in see level - basic Archimedes' principle about buoyancy. presumably only ice not floating- land ice- leads to sea level change? exactly how much perminate ice on earth falls into this catagory and could contribute to sea level rise.

    2) volcanos regularly produce millions of tonnes of greenhouse gases, how do the amounts of greenhouse gas from volcanoes and other natural sources compared to that which is man made. i accept that even if human gases are only a small fraction they could tip the balance between CO2 sources and sinks but massive volcanic eruptions arnt very frequent so the amount of gas they give out would be a useful comparision to total human emissions in say a year

    hope someone can answer these questions for me, it seems to be very hard to find straight answers to simple questions on climate change.

     
  • At February 09, 2008 2:02 AM, Anonymous Mr Penticol (scientist) said…

    What these idiots fail to notice, every single year, is that millions and millions of kmĀ² of ice melts in the antarctic, and freezes again a few months later. It does this every year. Does the sea level go up? Does it go down? No.
    Stop lying to people about global warming. When you get found out, people will never trust scientists again over climate, and the result of that will be that they won't give a shit about the environment.

     
  • At February 09, 2008 8:43 AM, Blogger coby said…

    Two minor points that have escaped you, Mr Penticol (scientist):

    1. The oceans are huge and the *billions* of *km^3* of net ice loss each year result in small numbers of millimetres of sea level rise. (as opposed to your concern about *millions* of *km^2* - square km, do you mean sea ice extent??)

    2. When it melts in the antarctic it freezes in the arctic, and vice versa.

     
  • At July 11, 2008 11:09 PM, Blogger yezi said…

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