Naked Science Forum
General Science => General Science => Topic started by: Eric A. Taylor on 18/11/2009 14:50:10
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Dr. Jonathan Bamber [originally post said "Banper", ed] sated on the Naked Scientists that Greenland contains enough ice to raise sea level by 7 meters. I did some math. I might be wrong, I'll provide the stats so you can check my calculations.
World wide the Earth's oceans have 3.352581414 square meters of area. So to raise sea level by 7 meters you will need AT LEAST 2.3468061515 cubic meters of water. This number is a bit low because quite a bit of land area is less than 7 meters above sea level. The ocean's area will increase by the number of square meters that are less than 7 meters above sea level.
Greenland has 2.1660861212 square meters of area. It's ice would need to be AT LEAST 1109 kilometers thick (when melted) to have this much water. Remember that water expands when frozen so the would be the depth of a tank the size of Greenland when filled with all of Greenland's melted ice.
If this is right then, in the wonderful parlance of Britain's parliament, "the right honourable Doctor" is full of Bull- sorry male bovine faecal matter.
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http://www.esa.int/esaEO/SEMILF638FE_planet_0.html
The european space agency quote an average thickness for the greenland ice sheet of 2.3 km.
So your calculations agree reasonably well with the figures quoted, actually...
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Oh, and... need you be so, um, confrontational? It's not really called for, especially when you appear to be calling an error that doesn't exist...
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well first 2.(point)3 kilometers is far short of 1109 kilometers. Sorry forgot Europeans use comas instead of periods for decimal places. That's one THOUSAND kilometers.
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Sorry forgot Europeans use comas instead of periods for decimal places.
The British one's don't!
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So, we do agree that a global sea level increase of 7 meter increase was a mistake? What is the correct number then? 1/482 of the amount? 14.52 mm? Or at least thereabouts?
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Something to keep in mind. The Ocean is huge. To get a sea level rise of just a few inches (or cm) takes an incredibly large amount of water. If you have a field that is 1 kilometer square and you wish to flood it to 1 meter deep, not even really deep enough to swim in you will need 1 million 16 cubic meters of water. 1 cubic meter of water is 1000 liters (God I love metric) so 1 million cubic meters of water will be 19 liters. My 4x4 pickup gets about 20 miles to the gallon of petrol so 8.5 K/L. On that much gas I could drive 8.59 kilometers. At 100 KPH I'd run out of gas in about 9700 years. And this is just 1 square kilometer flooded to 1 meter deep. Multiply all these numbers by 7 if you want to get the assumed sea level rise for one single square kilometer. You'll need to multiply your 7 meter depth numbers by a whopping 361 000 000 (million) because all of the worlds connected ocean is 361 million square kilometers. It's hard to even imagine that much water. About 2.52718 liters. How long will THAT last in my truck. 2.4513 years considering that this is nearly 1800 times the current age of the universe I think the term "forever" might be applied here.
Truth be told, England and Europe will not have to deal with 7 meters higher seas, but dumping large amounts of cold, fresh water into the North Atlantic will be very bad news for you. Likely it will disrupt the Gulf Stream which brings quite a lot of heat from the West Atlantic to warm Europe, especially in the winter. If this happens you might want to invest is snow removal equipment and polar clothing because it's going to become quite cold there. Rome may become a great spot to hold the Winter Olympics.
Climate change is happening, as it has always happened, and man has very little to do with it. Thus there is little man can do about it. And Al Gore did NOT invent the internet
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(...)
Climate change is happening, as it has always happened, and man has very little to do with it. (...)
Now go convince the AAAS because they seem to think that man plays a part bigger than "very little".
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Let's get the maths right chaps.
1. The area of the world's oceans is about 335,000,000 sq km
2. The area of Greenland (80% covered with ice) is 2,180,000 sq km
3. The ice thickness is 2 to 3 km thick but, of course, varies. The estimated total volume of ice is 2,850,000 cubic km.
The ocean level rise is therefore:
2,850,000/335,000,000 = .0085km = 8.5m
Allowing for the lower density of ice (about 0.92 that of water) the result can be corrected to about 7.8m.
If you also assume that the ocean level rise will find its way into all the seas on the earth then this number further reduces by a factor 335/361 to give 7.2m as was stated.
I will allow that the rise would be a bit less than this because of the extra area of water after it has consume vast tracts of land through flooding, but the original statement of criticism is clearly not correct. The situation is much worse should the antarctic ice melt too by the way.
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Dr. Johnathan Banper(?) sated on the Naked Scientists that Greenland contains enough ice to raise sea level by 7 meters. I did some math. I might be wrong, I'll provide the stats so you can check my calculations.
World wide the Earth's oceans have 3.352581414 square meters of area. So to raise sea level by 7 meters you will need AT LEAST 2.3468061515 cubic meters of water. This number is a bit low because quite a bit of land area is less than 7 meters above sea level. The ocean's area will increase by the number of square meters that are less than 7 meters above sea level.
Greenland has 2.1660861212 square meters of area. It's ice would need to be AT LEAST 1109 kilometers thick (when melted) to have this much water. Remember that water expands when frozen so the would be the depth of a tank the size of Greenland when filled with all of Greenland's melted ice.
If this is right then, in the wonderful parlance of Briton's parliament, "the right honorable Doctor" is full of Bull- sorry male bovine fecal matter.
I think you have added a spurious x 103 in your calculations. Using your base figures, I get a required ice depth of ~1109 metres, not ~1109 kilometres.
If the area of the world's saltwater is 335.258 x 1012 square metres, the required volume to increase the water level by 7 metres will be 335.258 x 1012 x 7 = 2346.806 x 1012 cubic metres.
The area of Greenland is 2.166 x 1012 square metres, so the required depth of ice on Greenland is 2346.806 x 1012 / 2.166 x 12= 1082.474 metres.
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...and allowing for the other factors that graham.d mentions above means that the given answer seems about right.
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...and allowing for the other factors that graham.d mentions above means that the given answer seems about right.
Yikes!
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I had a look on Google earth.
Greenland is rather big.
It's rougly 2 inches by 1 on my screen. The earth is roughly 9 inches in diameter on the same scale.
So that's roughly 2 square inches in 65 square inches. Of course, the projection of the earth onto the screen distorts the area. If I remember rightly that gives rise to a factor of about 2 in the true area. There's also the other side of the world so that's another factor of 2.
So Greenland is roughly 2/(65*2*2) of the earth's surface- about 1/130.
If the ice now on greenland were spread across the whole earth (not a bad aproximation to the area of the oceans- the earth is mainly covered in water) then it would be about 130 times thinner.
If it starts off 2.3 Km thick then it would raise the sea levels by 17 m.
Obviously there are a whole lot of iffy aproximations here but the answer is a lot nearer to 7 metres than half an inch or so.
BTW, have you seen how big Antarctica is? If that melts we are in trouble.
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That does it.
I'm flogging the house and buying the biggest yacht I can get for the money.
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So how much will the ocean rise if Antartica melts as well?
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So how much will the ocean rise if Antartica melts as well?
It's quite close to you. Could you nip down there and measure the amount of ice for us?
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Oh! I guess he's not back yet. While we're waiting, here's a clue.
Greenland has an area of 2.16 million square kilometers.
Antartica has an area of 14 million square kilometers.
So, assuming my $3 calculator is not lying again (it hasn't quite recovered from the coffee mug incident), Antartica could have 6.5 times as much ice as Greenland.
Ignoring minor details like how thick the ice actually is, if it was ALL to melt we might conclude that sea level would rise by 45.5 m. Adding the 7 m or so from Greenland would make a total of 52.5 m.
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Perhaps I should run a poll on how many of us live below 50m above sea level.
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Let's get the maths right chaps.
1. The area of the world's oceans is about 335,000,000 sq km
2. The area of Greenland (80% covered with ice) is 2,180,000 sq km
3. The ice thickness is 2 to 3 km thick but, of course, varies. The estimated total volume of ice is 2,850,000 cubic km.
The ocean level rise is therefore:
2,850,000/335,000,000 = .0085km = 8.5m
Allowing for the lower density of ice (about 0.92 that of water) the result can be corrected to about 7.8m.
If you also assume that the ocean level rise will find its way into all the seas on the earth then this number further reduces by a factor 335/361 to give 7.2m as was stated.
I will allow that the rise would be a bit less than this because of the extra area of water after it has consume vast tracts of land through flooding, but the original statement of criticism is clearly not correct. The situation is much worse should the antarctic ice melt too by the way.
I have just redone my math. It would appear I've misplaced a decimal point. I'm terribly sorry. There is no excuse aside from the fact that I'm human and apparently made an error in while converting kilometers to meters. Considering ESA and NASA engineers made mistakes converting metric to English measuring systems leading to the loss of a Mars probe I hope the people of this forum can find it in there hearts to forgive me.
I am in fact very happy that the Naked Scientist is free of fecal matter of any kind.
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Perhaps I should run a poll on how many of us live below 50m above sea level.
I live 210 feet above sea level so I'm good.
In the 1990's several dikes in the Sacramento River Delta broke and flooded quite a lot of farm land. California contacted some Dutch engineers to teach them how to build better dikes. I think we need to call those guys back. Is it possible to build dikes that tall?
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Thank you for showing great humility, Eric; I'm pleased that we have passed the accuracy test on this occasion.
Thank you also to those who carefully re-checked the sums.
Chris
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I am in fact very happy that the Naked Scientist is free of fecal matter of any kind.
I'm not sure I would go that far! [;D]
Anyway, 2015 feet, ....erm, I meant to say 614 m
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Oh! I guess he's not back yet. While we're waiting, here's a clue.
Greenland has an area of 2.16 million square kilometers.
Antartica has an area of 14 million square kilometers.
So, assuming my $3 calculator is not lying again (it hasn't quite recovered from the coffee mug incident), Antartica could have 6.5 times as much ice as Greenland.
Ignoring minor details like how thick the ice actually is, if it was ALL to melt we might conclude that sea level would rise by 45.5 m. Adding the 7 m or so from Greenland would make a total of 52.5 m.
Sorry I don't own a boat :p
But another factor that might be overlooked is the fact that as circumference increases, it will take more water to raise the ocean by a certain level.
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I have every intention of continuing to overlook the effect of an increase in circumference that's roughly in proportion to the change in radius from 6378.1 km to 6378.2 km, not least because I live about 100m above sea level
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I have every intention of continuing to overlook the effect of an increase in circumference that's roughly in proportion to the change in radius from 6378.1 km to 6378.2 km, not least because I live about 100m above sea level
You may also want to overlook the fact that as the ice on Antarctica, and Greenland come to that, melts, the land surface will rise because it has a lot less weight to support. This increase in elevation will offset some of the tendency for the remaining ice to melt, but I doubt that it will be all that significant.
Where are all the geologists when we need them? Off playing with their rocks, I suspect.
BTW, at 100m you'll be pretty much "beachfront".
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Sorry I don't own a boat :p
No, I meant you to take your plane. All Australians have planes so they can get around those gigantic sheep stations, don't they?
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I am in fact very happy that the Naked Scientist is free of fecal matter of any kind.
I'm not sure I would go that far! [;D]
Anyway, 2015 feet, ....erm, I meant to say 614 m
Are you sure it's not 6.14 meters? Those d. points are tricky bastards. Why is it when they make mistakes on paychecks it's always moving the d point to the left instead of the right?
That's not completely true. I once got a paycheck for $5589.50 for what my pay should have been $558.95. I took my check to payroll and asked if I was getting a bonus. The head of payroll said I had been issued a bonus, when I said that a $5000 bonus was very nice, they drew me a new check for $600. The bonus was suppose to be 10% but it was made 1000% by mistake. Oh well. At least I got some bonus.
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I have every intention of continuing to overlook the effect of an increase in circumference that's roughly in proportion to the change in radius from 6378.1 km to 6378.2 km, not least because I live about 100m above sea level
You may also want to overlook the fact that as the ice on Antarctica, and Greenland come to that, melts, the land surface will rise because it has a lot less weight to support. This increase in elevation will offset some of the tendency for the remaining ice to melt, but I doubt that it will be all that significant.
Where are all the geologists when we need them? Off playing with their rocks, I suspect.
BTW, at 100m you'll be pretty much "beachfront".
This land rise will take several million years to take place. The land in southern Canada and Northern US is still rising quite quickly after thick glaciers melted away in North America at the end of the last ice age.
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Sorry I don't own a boat :p
No, I meant you to take your plane. All Australians have planes so they can get around those gigantic sheep stations, don't they?
Hey "mate" not all Australians live in the bush. Did you know that Australia is one of the only countries to lose a head of state in the 20th Century? I don't have the name handy but can add it later when I have time to look it up. One of their presidents went for a dip in the ocean and disappeared. His body was never recovered. Can you imagine how THAT was explained? I know Australians tend to be a little laid back, but come on!
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We don't have heads of state or presidents, we have Prime Ministers, but yes I believe you refer to Harold Holt who drowned at Cheviot Beach. Of course there are all kinds of theories that he faked his own death etc. but the fact is Cheviot beach is notorious for rip tides and the surf was heavy at the time, even the strongest of swimmers can find themselves in trouble before they know it.
Sorry I don't own a boat :p
No, I meant you to take your plane. All Australians have planes so they can get around those gigantic sheep stations, don't they?
Oh, yes of course. Unfortunately my plane is not in working order at the moment, it was damaged by bunyips
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I would try and tease you for the bunyips, but as New Zealand will pretty much be underwater, I might have to jump ship so to speak.
It would be so much better if the sea levels fell, we would gain land instead of contantly losing it.
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Oh, yes of course. Unfortunately my plane is not in working order at the moment, it was damaged by bunyips
Look out! You can be sure they left a defugalty in your nav system. And don't be surprised if they reversed the thread on the prop so it falls of the first time you try to use it.
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Nah, she'll be right mate!