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Question about sea levels and ice melting.


blackhole123

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I've seen people claiming the oceans will rise 20 feet if Antarctica melts. Why then, with the seasonal melting of half the continent, do sea levels not rise and fall every year by 20 feet? I think the answer has something to do with the ice already being in the water so when it melts the level is still the same, but then what other is global warming melting? I thought so far it is just that less and less ice is refreezing, which would mean that it has not changed sea levels at all yet.

 

How could it change sea levels?

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Oh, it'll rise a LOT more than 20 feet - the actual estimate is 60 meters.

 

The discrepancy is because the seasonal change is nowhere near 50% over the whole continent. I think that figure is just for a subset of ice (such as 'pack ice' formed from seawater), but I can't find good figures for the life of me.

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The pack ice is ice floating on water. The melting and refreezing of this has no effect on sea level. Ice on land is another matter, and if it melts it will raise sea level a lot.

 

Predictions are rife with potential error. You will see an enormous range of sea level rise predictions. Take with a good pinch of salt.

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Predictions are rife with potential error. You will see an enormous range of sea level rise predictions. Take with a good pinch of salt.

 

How much error, do you estimate, is contained in the prediction of how much the sea level would rise if all of the Antarctic ice melted?

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And further, if you've got a problem with prediction, you can instead focus on forensics and still pretty much get the same conclusion.

 

Watch this. It's split into six very informative chapters. Enjoy.

 

http://www.pbs.org/wgbh/nova/extremeice/program.html

 

 

 

As for the OP, it's already been answered. The difference here is that it is the ice from on top of land melting and flowing into the ocean. During normal seasonal melts it is primarily ice already in the water that melts, not ice on land. This is why normal seasonal changes don't have as large an impact, but continued warming will make sea levels rise due to addition of ice to the system, ice previously resting on top of land.

 

Watch the Extreme Ice special from NOVA above. It's worth it.

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The error factor in sea level predictions can be obtained form looking at the predictions themselves.

 

Current sea level rise is 3 mm per year. If this continued at this rate, the sea level rise by 2100 would be 273 mm - or a little less than one imperial foot.

 

IPCC have varied their predictions from 300 mm to one metre. Dr. James Hansen, an eminent climate scientist, has published an opinion that sea levels will rise by 5 metres by the year 2100.

 

Thus, sea level rise predictions are highly variable, illustrating the error factor in such predictions.

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The error factor in sea level predictions can be obtained form looking at the predictions themselves.

 

Current sea level rise is 3 mm per year. If this continued at this rate, the sea level rise by 2100 would be 273 mm - or a little less than one imperial foot.

 

IPCC have varied their predictions from 300 mm to one metre. Dr. James Hansen, an eminent climate scientist, has published an opinion that sea levels will rise by 5 metres by the year 2100.

 

Thus, sea level rise predictions are highly variable, illustrating the error factor in such predictions.

 

 

That wasn't the question, though. The OP doesn't mention annual rates, or predictions based on Hansen or the IPCC. The question was what the sea level rise would be if the Antarctic ice melted.

 

So I will ask again: How much error, do you estimate, is contained in the prediction of how much the sea level would rise if all of the Antarctic ice melted?

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Swansont

I have not suggested I know the answer to that question. What I said was that predictions contain a substantial error factor. To answer your question would require a knowledge of how the total tonnage of ice in Antarctica was estimated. Even that would be incomplete knowledge, since isostatic rebound after melting will have an effect also.

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Swansont

I have not suggested I know the answer to that question. What I said was that predictions contain a substantial error factor. To answer your question would require a knowledge of how the total tonnage of ice in Antarctica was estimated. Even that would be incomplete knowledge, since isostatic rebound after melting will have an effect also.

 

No, you just suggested that there's a good chance any answer given will be wrong, and wrong by lot.

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Swansont

What I said was :

"Predictions are rife with potential error. You will see an enormous range of sea level rise predictions. Take with a good pinch of salt."

 

Please do not put words in my mouth. This is the science forum and you are supposed to make an effort to be accurate.

 

My statement above is accurate, and supported by the facts. Predictions of sea level rise that range from 300 mm to 5 metres by the year 2100 are consistent with that statement.

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Swansont

What I said was :

"Predictions are rife with potential error. You will see an enormous range of sea level rise predictions. Take with a good pinch of salt."

 

Please do not put words in my mouth. This is the science forum and you are supposed to make an effort to be accurate.

 

My statement above is accurate, and supported by the facts. Predictions of sea level rise that range from 300 mm to 5 metres by the year 2100 are consistent with that statement.

 

You didn't make the latter point, with the numbers, in the same post where you said "Predictions are rife with potential error. You will see an enormous range of sea level rise predictions. Take with a good pinch of salt."

 

So your later-quoted numbers mat be accurate, but my point is that this is a non sequitur. Nobody but you has said anything about global warming predictions. What was asked was very specific: IF the antarctic ice were to melt, by how much would the sea level rise. Mokele answered the question. There should have been nothing to add to it, but your post implies that the ~60m number is in serious question. Is it?

 

Where did I put words in your mouth, as you accuse me of doing? Use the quote function (for once)

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Swansont

All is context. I was talking of sea level rise predictions. Your criticism did not relate to this.

 

And if every thread in this forum ended when the OP was answered, we would have a hell of a lot of very short threads! My observations are that most threads continue after the basic query is answered. This is called 'normal'.

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iNow

 

You may not realise it, but your continuing accusations that I fail to use references is getting downright annoying. I suspect that it is a case of the pot calling ....

 

In order to check this scientifically, I went back to the thread that you were most vitriolic about - guns and suicides, and reviewed each and every reference posted by everyone on that rather long thread.

 

I can post the detailed results if you like, but here is a summary.

 

SkepticLance references - 14

References posted by everyone else put together - 19

iNow references - 4

 

The iNow references were all utterly useless.

The first one I could not access at all, and I do not know if it was genuine or not.

The other three were all the same - a reference to a previous thread on pit bull attacks. This was by way of making a snide remark to suggest that I was using poor logic in two threads, not one. It was irrelevent, personal, insulting, and inaccurate, and an excellent example of lousy science.

 

iNow

If you want to start making accusations, I suggest you get your own act together first. You have a long history of making insults plus snide and sarcastic remarks, and in this case of failing to meet the standards you accuse me of not reaching.

 

The basic rule is, if you cannot say something constructive, then shut up!!

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iNow, don't drag old disputes into new pages. If you want references, just ask.

 

SkepticLance, if someone asks, you should be ready to provide references, whether or not they ask in what you consider a polite way.

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iNow, don't drag old disputes into new pages.

That's a rather difficult request, but I understand your concern and will certainly try. I think perhaps the last few posts should be split into their own thread or merged with the one to which I linked, but that is obviously a decision for you all on the staff. Enjoy.

 

 

 


Merged post follows:

Consecutive posts merged
I can post the detailed results if you like, but here is a summary.

 

SkepticLance references - 14

References posted by everyone else put together - 19

iNow references - 4

 

The iNow references were all utterly useless.

Feel free to use the quote feature to specify which of my comments/posts require citations and I will happily oblige.

 

 

The basic rule is, if you cannot say something constructive, then shut up!!

 

I find my desire for accuracy, precision, and evidence to be INCREDIBLY constructive, but YMMV.

Edited by iNow
Consecutive posts merged.
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Swansont

All is context. I was talking of sea level rise predictions. Your criticism did not relate to this.

 

You did not make this clear in your first post. i.e., you did not provide context for your comment.

 

The answer to "How much will the sea level rise if all the Antarctic ice melted" is a sea level rise prediction, albeit a very specific one. Do you have any legitimate reason to doubt that the 60m prediction is reasonably accurate, say to within 10%?

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Swansont

Given suitable error factors, that is probably an accurate statement. I read an estimate a while back that Antarctica and Greenland together hold ice to the equivalent of a sea level rise of nearly 90 metres, which is consistent with your statement.

 

Also, we know that the end of the last glaciation period involved a sea level rise of major proportion - over 100 metres. From the peak glaciation about 18,000 years ago, to about 12,000 years ago, sea level rise in some places may have been as much as 150 metres. In fact, sea level rise has continued, albeit at a slow pace, to this day.

 

The real issue is whether there is any danger of a substantial part of Greenland and Antarctic land ice melting over the next 100 years.

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There are people who will try to suggest that Antarctica and Greenland are about to discharge their ice cover into the sea, and flood the world. In fact, that is extremely unlikely. Antarctica, for example, has an average temperature of minus 50 C.

http://www.antarcticconnection.com/antarctic/weather/climate.shtml

 

The biggest warming that has occurred in Antarctica has been on the Antarctic Peninsular, and amounts to less than 3 C. The rest of the continent has warmed to a level that is almost zero. To melt all the ice on Antarctica would require an enormous temperature increase. Seriously unlikely.

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To melt all the ice on Antarctica would require an enormous temperature increase. Seriously unlikely.

No, it wouldn't, as demonstrated in the link I've shared now twice already in this thread. You are working from an old premise which has been proven false... You think that "there's simply too much ice" and that "the temperature will need to rise too much to melt it all" for us to worry about it.

 

That assumption is plainly false, and my link amply supports my assertion that you are mistaken on this point. This is not personal, and this is not an attack. This is a truth being shared which counters your assertions squarely and robustly.

 

To be fair to you, I also thought the same thing... That there was simply too much ice for us to worry much yet. However, due to the increasing frequency and interplay of calving, melt water runoff, subsurface pressures, the lubrication effect of the melt waters which erode the structure and flow below the ice sheet (also presenting additional issues of pressure making the faults more severe), and the fact that cooler waters flowing into the ocean create a vacuum pulling the warmer waters from deeper even further under the ice sheet, hence resulting in further melt and faults... the simple fact is that the "seriously unlikely" situation you are classifying is much more accurately described as "very very very likely" to happen quickly. It's also happening already, as evidenced in the forensic studies shared at the link I provided.

 

Long story short, though... Your premise is faulty, hence your conclusions wrong, and I want to work with you to better understand this new information which is available to us. If you're not willing to watch the special I shared, then at least explore the first site linked below which explains it better than I can:

 

http://www.extremeicesurvey.org/index.php

http://www.pbs.org/wgbh/nova/extremeice/

http://www.pbs.org/wgbh/nova/extremeice/program.html

Edited by iNow
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iNow

It appears that I cannot watch your reference. The link carried a message that it was not available to me since I lived outside the USA.

 

I read the summary sections, and it appears that nothing there relates to the main part of Antarctica, which is what my last post was about.

 

I repeat my message. There is no realistic chance that the vast bulk of the ice in Antarctica will melt any time in the next 100 years. Probably not any time in the next 1000. There is ice melt in the Antarctic Peninsular. However, that small part of the total appears to behave in terms of ice melt as if it were a part of a different country. The peninsular is a relatively tiny part of the whole, and supports a tiny part of the total ice mass.

 

Here is a more sceptical view of the Antarctic ice melt.

http://www.ecoworld.com/blog/2008/04/17/antarcticas-ice-mass/

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iNow

It appears that I cannot watch your reference. The link carried a message that it was not available to me since I lived outside the USA.

I'm sorry to hear that. It was a good special. However, I did summarize the key bits in my main paragraph above. The issues are warmer ocean water being pulled beneath the ice sheet due to the pressure differential after cooler fresh water flows from the top of the ice sheet into the ocean. There is also the issue of lubrication, causing the ice sheet to move much more quickly than previously thought possible. Additionally, the calving and splitting creates further calving and splitting due to erosion and pressure of the water within the ice sheet itself.

 

Despite our intuitive notions that the ice sheet is simply too big and too vast to be impacted by minimal warming, the data shows our intuitions to be misguided and simply wrong. The ice sheet is going away my friend, and it's happening quickly.

 

 

I read the summary sections, and it appears that nothing there relates to the main part of Antarctica, which is what my last post was about.

The entire special was about Antarctica and Greenland, so it is quite relevant. Again, I am sorry you were not able to review it personally to confirm this.

 

 

I repeat my message. There is no realistic chance that the vast bulk of the ice in Antarctica will melt any time in the next 100 years. Probably not any time in the next 1000. There is ice melt in the Antarctic Peninsular. However, that small part of the total appears to behave in terms of ice melt as if it were a part of a different country. The peninsular is a relatively tiny part of the whole, and supports a tiny part of the total ice mass.

Again... No. Just because you were unable to retrieve the reference does not mean your claim is still valid. The reference flatly and resolutely shows your statement false, and I implore you to (at the VERY least) stop repeating it until you are able to review the data which proves you mistaken.

 

This isn't about skepticism. This isn't about predictions or models. This is being witnessed right now. This is about forensics, and all of the posts and waving hands in the world claiming otherwise cannot overturn the evidence I have cited here.

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Here is a more sceptical view of the Antarctic ice melt.

http://www.ecoworld.com/blog/2008/04/17/antarcticas-ice-mass/

Yes, and that's all it is: a sceptical view.

 

In the blog post (ahem), Ed Ring dissects a BBC news article and disagrees with some of it. As far as the study goes he did exactly what you did:

The story referenced a study by “a UK/Finnish team” - we couldn’t find the actual study online - that concluded “Sea levels could rise by up to one-and-a-half metres by the end of this century, according to a new scientific analysis… substantially more than the Intergovernmental Panel on Climate Change (IPCC) forecast in last year’s landmark assessment.”

 

Failing to access the data is not a rebuttal of the data.

 

I'd also point out that the article is a year old now, and a lot of the EIS data has been collected in the interim.

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