Earth's Polar Ice Caps Melting this Summer?

[Monte314]

It was recently suggested by two American scientists that, for the first time in recorded history, the north polar ice cap could melt completely this Summer.

Suppose that they are right, and the north polar ice cap does melt completely, but that other land-based pack-ice farther south does not melt. What would be the effect on sea level?

We consider this by asking the following question. Suppose you have a big tank of water with a large, free-floating block of ice in it. You notice that, because ice is less dense than water, a significant amount of the ice block sticks out above the level of the water. When the block melts, this unsubmerged ice will become a liquid, and will be added to the tank with the rest of the water.

You mark the present level of the water in the tank. Assuming that there is no evaporation, when the block of ice has completely melted you will notice that one of the following has occurred:

1.) The water level in the tank is lower.
2.) The water level in the tank is the same.
3.) The water level in the tank is higher.

Based upon whether you think the outcome will be 1, 2, or 3, what do you think the effect on coastal cities will be if the polar ice-pack melts completely?

[TheLastMohican]

I will be devastated if a fellow INTJ gets this one wrong. ;)

I think of the melting as good news. The Northwest Passage is what we've been waiting for for hundreds of years. I hope it gets used.

[thegnat]

Yikes, that's awful news to hear. Personally, I think coastal cities could get flooded. I don't know how much the north ice cap melting could affect volume near local cities but it could have seriously bad effects.

I've heard quite a few things could happen.
1) a current stops in the arctic ocean and disastrous things happen with ocean and temperatures and climate effects in general. The ocean currents are important to spread temperatures and humidity around the world. And dramatic climate changes could happen IN OUR LIFETIME if that current is disrupted up near the North Pole.
2) more volcanic eruptions
3) Sea levels rising.
4) related to 2 - more magma getting freed with hotter water.

Monte: Even though ice is less dense than water, a majority of the ice will be submerged. When you see icebergs, a good majority of their mass is actually underwater.

Due to the volume displaced by the submerged part of the ice berg, if that part only melted, the level may stay the same. However, you have parts of the iceberg above the water. Another thing to take into consideration is average temperature of the water when this happens.

[wolf]

Monte314: 2.

But since the ice is fresh water and the ocean is salt water, 1.

Regardless, much drinking and partying will occur in PB.

[Marcus]

There is ice (to melt) over land, too:

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“That may not sound like a lot, but consider the volume of ice now locked up in the planet’s three greatest ice sheets,” she writes in a recent issue of Scientific American. “If the West Antarctic ice sheet were to disappear, sea level would rise almost 19 feet; the ice in the Greenland ice sheet could add 24 feet to that; and the East Antarctic ice sheet could add yet another 170 feet to the level of the world’s oceans: more than 213 feet in all.” Bell underscores the severity of the situation by pointing out that the 150-foot tall Statue of Liberty could be completely submerged within a matter of decades.

Whew, I live 200m (328 feet) above sea level.

[wolf]

The earth once looked like that, and it would again, no matter what we tried to do to stop it.

However, if it all melted out it would suck because my airport would be underwater...

[konec]

There is ice (to melt) over land, too:

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Whew, I live 200m (328 feet) above sea level.

10 cm (4 inches) below sea level here :cry:

[wolf]

I just grabbed the google earth ocean depth change thing, and it looks like at the maximum it'd leave much of Los Angeles under water. I'm above water, but just barely. The weather here would be freaking awesome year-round if all the ice melted and I'd be within a short walk of the beach - major bonus.

My grandfather and grandmother are buried just above the maximum sea level on the island that will remain of a portion of Los Angeles. Where I grew up would be beach-front property, with the ocean running up to the street directly behind it. How's that for awesome real estate in the middle of a ghetto?

I approve of this melting.

Edit: Interesting, I just realized that my other grandparents, great grandparents, great-great grandparents, and numerous relatives buried in the Los Angeles area will also be above water... Sweet.

Edit: It would also reattach the Salton Sea to the ocean and fill all the way up to the suburbs of Palm Springs. It might even make that area livable again... heh.

[Marcus]

10 cm (4 inches) below sea level here :cry:

What to say? Konec... :(

[PHS Philip]

TLM, the Northwest Passage opened last year, too. It just didn't go right over the pole.

A lot of this area has melted the past few years, so I doubt that this will have too much of an effect. There'll be a bit of a rise, but not much more than we have already. This is more a big deal symbolically than as an actual threat. It will take a LOT of melting for it to have a major effect, except maybe for places like Florida where a few inches more will cover sizable portions of the state.

If the big ice sheets melt, several things will happen. First, Florida will vanish. Most coastlines will be gone, although how far they get pushed back depends on the type of coast, and steepness of it. Any saltwater marshes will be gone.

The ocean conveyor belt current may stop, although that's not certain. If it does, most of Europe will end up as tundra, and all but the most local (IE onshore offshore breezes) ocean driven weather patterns will change. This will result, of course, in droughts all over the world, floods all over the world, and the like. However, climatologists can't really say with any certainty where this would happen. All that can be said is that it would.

Beyond that, I don't know. There are probably more predicted effects, and probably more effects that no one has predicted yet. It's enough to say that, unless we're ready for it, the effects will be very, very bad.

[TheLastMohican]

TLM, the Northwest Passage opened last year, too. It just didn't go right over the pole.

I know. But currently the time period is too brief to make it a reliable path. The more melting, the more time each season we will have during which we can safely plan to ship through the passage, without icebreakers. Eventually we can have a regular business going across, without waiting uncertainly each year for the ice to melt.

[Monte314]

Answer to the original question:

If the tank contains pure water, the level of the water will be *unchanged* after the ice melts. This is relatively easy to show mathematically, and by experiment (leave a glass of water with a with a single free-floating ice cube out on the coffee table).

As was pointed out in this thread, however, sea water is salty, and ice is essentially pure; this is because water drops its minerals as it freezes. Therefore, sea water is slightly denser than the water that the melting ice will produce, so the water level will be increased by the melting, but only very slightly (in fact, by the ratio of the densities, which is only slightly larger than 1).

If the north polar ice cap melts completely, it will *not* produce catastrophic flooding of coastal cities. Of course, if land-based glacial ice melts, too, that could be a different story.

[wolf]

Wouldn't the fresh water mix with sea water and gain the same composition as the existing sea water? It would probably change the salinity profile, though, so I may be missing something.

Yes, the melting of land-based ice could rapidly increase the depth of the oceans, and would certainly have an effect.

[Monte314]

Wouldn't the fresh water mix with sea water and gain the same composition as the existing sea water? It would probably change the salinity profile, though, so I may be missing something.

Yes, the melting of land-based ice could rapidly increase the depth of the oceans, and would certainly have an effect.

Yes, you are right. The computation just looks at the "before" and "after" depths, and does not consider how the process would unfold. But, it is designed to give a correct final state.

If the land-based ice melts, we are going to have bigger problems than trying to dry out flooded ports. But I don't see this happening.

There is something weird going on with the Sun right now, though. I track the sunspot cycle (for my astronomy), and noted that the normal 11-year cycle is out of whack. There have been almost no sunspots for the last two years. I did some checking, and, sure enough, solar astronomers have been talking about this. But, this is not the first time this has happened, so I guess we're not all going to die....

[thegnat]

Wouldn't the fresh water mix with sea water and gain the same composition as the existing sea water? It would probably change the salinity profile, though, so I may be missing something.

Yes, the melting of land-based ice could rapidly increase the depth of the oceans, and would certainly have an effect.

I would think that the fresh water would have to mix eventually, but perhaps due to the densities of the respective "waters" perhaps the region around melting ice is a significantly less salty region until it has had a chance to mix in with the salt water. Now I'd like to do an experiment with salt water and an ice cube....

I'm thinking, maybe it would need some mixing and perhaps it'd form a little layer in completely calm waters. It's not like pouring in fresh water to salt water, because the water that's melting is going to come from the surface. Not from the part that's below the water because the sun will hit the portion that's above the water, then it would be a little smaller, move up again, melt again, move up again and so forth. Pouring water would mix it a bit because the water being poured is going to penetrate the surface a bit and probably mix a bit more than meltwater.

And yes, the land-based is the kind we really need to be concerned about...And I do think that's going to be an issue. The less sea ice, the less cool the arctic is in general, the more likely land-based ice is going to melt. And the rate keeps accelerating as more ice melts.

[wolf]

Yes, you are right. The computation just looks at the "before" and "after" depths, and does not consider how the process would unfold. But, it is designed to give a correct final state.
That is assuming the fresh water remains fresh water and reduces the salinity of the ocean permanently.

If the land-based ice melts, we are going to have bigger problems than trying to dry out flooded ports. But I don't see this happening.
If it all melted overnight, it would displace or kill a large percentage of humanity. At least a billion would perish, and at least a couple billion more would be displaced. It would be a catastrophe of epic proportions.

There is some potential for acceleration related to the arctic ice sheet melting - if the permafrost melts, it will release vast quantities of methane gas that is trapped in the ice (which is many, many times worse than automobile and coal power plant emissions), and could rapidly increase the temperatures on this planet, perpetuating this effect.

There is something weird going on with the Sun right now, though. I track the sunspot cycle (for my astronomy), and noted that the normal 11-year cycle is out of whack. There have been almost no sunspots for the last two years. I did some checking, and, sure enough, solar astronomers have been talking about this. But, this is not the first time this has happened, so I guess we're not all going to die....
Don't sunspots reduce the surface temperature of the earth by reducing the amount of energy that makes it to us? This could easily explain our warming trend...

I would think that the fresh water would have to mix eventually, but perhaps due to the densities of the respective "waters" perhaps the region around melting ice is a significantly less salty region until it has had a chance to mix in with the salt water. Now I'd like to do an experiment with salt water and an ice cube....
Sea water salinity is highest at the surface, which is where you have the most activity (molecular and wave activity). You can't really do an experiment since the sea is far more complex than you could reproduce without a thousands-of-meters tall container of sea water that would reproduce the effects of the strata, then you'd still need to move the water as it does in the ocean. Below the high-salinity surface, the sea reduces in salinity until it hits a minimum trough at a certain depth (750m sticks in my mind), then it rapidly increases to somewhere between the surface and the low, and continues increasing gradually as you go deeper.

And yes, the land-based is the kind we really need to be concerned about...And I do think that's going to be an issue. The less sea ice, the less cool the arctic is in general, the more likely land-based ice is going to melt. And the rate keeps accelerating as more ice melts.
The Antarctic is more of a concern, since it contains a very large percentage of the world's glacial ice and could calve entire shelves, which would increase ocean depths rather dramatically. Greenland isn't a big deal. The entire northern hemisphere could melt and the effects would be manageable.

The fact is that Earth is just returning to normal. It has been unusually-cool on this planet within recent recorded history.

[Mozzes]

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I found this related article which I thought was interesting. It basically makes the argument that global warming is allowing taiga to move north which in turn will add to global warming by absorbing light that would normally be reflected back into space by tundra.

[antisocial one]

For original question about the ice. Sea level will drop because ice has 30% lower density.
But amount of drop will be so small that there will be no deference in practical sense.
Ice on the land is what will create problems in he future.

I think that people don't know about what kind of a changes we are facing here.

I am future geologist and I am doing my private research about this.
So give me few days to write something meaningful about this.

[thod]

For original question about the ice. Sea level will drop because ice has 30% lower density.

Although ice is less dense, that does not mean is displaces a greater volume of water. It simply means that more of it ends up sticking up above the surface where it displaces nothing. The overall sea level is not effected.

[wolf]

Yeah, density has nothing to do with mass. The ice currently displaces the same amount of water as it could add, though the water is fresh and will have slightly lower density than the surrounding water for a short time.

[Mozzes]

Yeah, density has nothing to do with mass. The ice currently displaces the same amount of water as it could add, though the water is fresh and will have slightly lower density than the surrounding water for a short time.

Density is defined physically as mass per unit volume. Since the density of liquid water and solid water have different densities differing phase compositions with a constant mass will necessarily occupy different volumes.

[antisocial one]

Although ice is less dense, that does not mean is displaces a greater volume of water. It simply means that more of it ends up sticking up above the surface where it displaces nothing. The overall sea level is not effected.

Maybe I am dumb but I don't get your logic that is for sure.

Let say that all ice is in the water. Then all ice melts.
But all icebergs have about 6/7 of its mass and volume beneath sea level. (Titanic story)
That means that iceberg has a certain volume but when it melts volume of water that was created is smaller.
But the part which was above water is reducing the diffrence.
1/7 is about 14% and diference in volume is 30% so there has to be a difference.

But on global scale that difference is so small that there is no real difference.
Melting of continental ice sheet is another story.

[TheLastMohican]

1/7 is about 14% and diference in volume is 30% so there has to be a difference.


But where did you get 6/7 and 30%? Ice has approximately 90% the density of water, so only about 10% of the volume of the ice is above the surface when it is freely floating.

[thod]

Maybe I am dumb but I don't get your logic that is for sure.

Look up Archimedes Principle. Steel is denser than water yet steel ships float.

[mkay]

I just grabbed the google earth ocean depth change thing....

Can you post the URL? Sounds fun to check out.

[Ice Wolf]

What about gravity?

Such large mass of ice have influence on gravitational potential.

Somehow i think that the sea level around north pole would actually drop. Of course this drop must be compensated elsewhere.

[antisocial one]

The density of pure ice is 0.9167 g/cm³ at 0°C.

But icebergs are not made of pure ice.

In this arcticle key word is snow.
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And now this site.

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Also icebergs are white and that means that they are full of bubbles filled whit air.
And pure ice is colourless.

So I have said 14% they say 12.5%.

And that 30% to be honest came out of my head and I did not check the data first.
So it looks like that real number is 20% maybe 25% in some cases.

What leads to conclusin that my prediction should be right but for a smaller degree.


But in the real world this entire way of thinking is flawed. because warming of the oceans is increasing volume of water. And ice sheets an glaciers are melting so there will be raise of sea level.
But in current situation sea level is the last thing we should be worried about.
True problem are droughts/floods.

[wolf]

Density is defined physically as mass per unit volume. Since the density of liquid water and solid water have different densities differing phase compositions with a constant mass will necessarily occupy different volumes.
You have added nothing.

The volume at the same phase will be identical, except that sea water is slightly denser than fresh water, which means it will cause a slight rise before the fresh water becomes sea water, at which point the level would be the same. We're also completely disregarding the highest-density state of water (which varies between fresh and sea/salt) that may be reduced, so we could potentially have slightly higher sea levels due to warmer sea water.

[thod]

How best to explain this?

Think about a balloon, when it floats most of its volume is above the waterline, The downward force is the mass of the balloon, the upward force is the mass of the water displaced. When the water turns to ice its volume increases but its mass stays the same. All that extra volume is simply pushed above the surface. There is no increase in the volume of water displaced. It doesn't matter if its full of air bubbles or not.

The thermal expansion of the oceans will increase sea levels, but that was not the question.

[wolf]

Thermal expansion isn't the problem, it's the reduction of water in the lowest-density temperature range that would have an effect.

[Mozzes]

You have added nothing.

The volume at the same phase will be identical, except that sea water is slightly denser than fresh water, which means it will cause a slight rise before the fresh water becomes sea water, at which point the level would be the same. We're also completely disregarding the highest-density state of water (which varies between fresh and sea/salt) that may be reduced, so we could potentially have slightly higher sea levels due to warmer sea water.

density = mass/volume.

If you consider in totality all of the water in the oceans, liquid and solid, you have an average density for that phase composition. If the ice all melts you'll generally have an increase in the average density. Since the total mass of all the water would be approximately constant the only way for the density to increase would for there to be a decrease in the volume. You said that the overall volume of the sea wouldn't change as a result of the ice melting (changing density) and I don't think that's the case.

Also, I don't really understand all this talk about "fresh water becomes sea water". Are we still talking about the polar ice? Isn't polar ice simply sea ice - frozen sea water? We wouldn't have to worry about density changes as it mixes with liquid sea water - at least not for that reason.

Of course we could make the whole scenario hopelessly complex - temperature change would affect gas solubility of the ocean, lack of ice would cause the ocean to absorb more light energy which would increase evaporation rates and temperature which would induce further thermal expansion, affect cloud formation, maybe affect global weather patterns in some way.

Admittedly I'm considering the problem on a superficial level but it is an incredibly complex to model accurately and there are too many variables for me.

[wolf]

I agree with that. Every time I think about it yet another variable comes up that throws the last theory off. It's not possible for me to answer this question based on all the variables involved, many of which I'm sure are missing.

Thermal expansion is negligible except that the densest water will be closest to the ice.

No, the ice cap is not frozen sea water.





wolf added to this post, 46 minutes and 23 seconds later...

Can you post the URL? Sounds fun to check out.
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Don't check them all, it freaks out when you do that. Turn on terrain (bottom checkbox in the current version of Google Earth) and check whichever depth you would like to see. It starts getting really interesting around ~6-8m in the Bay Area, then much more interesting at some slightly greater depths around where I am. NYC looks interesting pretty quickly, too...

[mkay]

Thanks, Wolf, for the URL as well as the warning. I'm an opportunist. I'm wondering whether any of this will make real estate more profitable in certain areas. When life hands you global warming, make lemonade! ... But I gather that this is happening slowly enough that I will be fertilizer before anything I buy could become valuable, lol.

[wolf]

Thanks, Wolf, for the URL as well as the warning. I'm an opportunist. I'm wondering whether any of this will make real estate more profitable in certain areas. When life hands you global warming, make lemonade! ... But I gather that this is happening slowly enough that I will be fertilizer before anything I buy could become valuable, lol.
The chance of seeing sea level rises over ~2-3m in our lifetimes is pretty low, and the absolute most/worst we could see is ~7-8m around 2050, at which point I'll be so old that I won't be all that bothered by it (in fact, it'll probably give me more interesting coastlines to sail my yacht along). If Antarctica melted, though, it would be rather dramatic, but the likelihood of this is extremely low.

[Tocsin]

I recently got pointed to this, and thought it might be... an ice breaker (sorry)... for this conversation:

On a planet 4C hotter, all we can prepare for is extinction
There's no 'adaptation' to such steep warming. We must stop pandering to special interests, and try a new, post-Kyoto strategy

Monday August 11 2008

We need to get prepared for four degrees of global warming, Bob Watson told the Guardian last week. At first sight this looks like wise counsel from the climate science adviser to Defra. But the idea that we could adapt to a 4C rise is absurd and dangerous. Global warming on this scale would be a catastrophe that would mean, in the immortal words that Chief Seattle probably never spoke, "the end of living and the beginning of survival" for humankind. Or perhaps the beginning of our extinction.

The collapse of the polar ice caps would become inevitable, bringing long-term sea level rises of 70-80 metres. All the world's coastal plains would be lost, complete with ports, cities, transport and industrial infrastructure, and much of the world's most productive farmland. The world's geography would be transformed much as it was at the end of the last ice age, when sea levels rose by about 120 metres to create the Channel, the North Sea and Cardigan Bay out of dry land. Weather would become extreme and unpredictable, with more frequent and severe droughts, floods and hurricanes. The Earth's carrying capacity would be hugely reduced. Billions would undoubtedly die.

Watson's call was supported by the government's former chief scientific adviser, Sir David King, who warned that "if we get to a four-degree rise it is quite possible that we would begin to see a runaway increase". This is a remarkable understatement. The climate system is already experiencing significant feedbacks, notably the summer melting of the Arctic sea ice. The more the ice melts, the more sunshine is absorbed by the sea, and the more the Arctic warms. And as the Arctic warms, the release of billions of tonnes of methane – a greenhouse gas 70 times stronger than carbon dioxide over 20 years – captured under melting permafrost is already under way.

To see how far this process could go, look 55.5m years to the Palaeocene-Eocene Thermal Maximum, when a global temperature increase of 6C coincided with the release of about 5,000 gigatonnes of carbon into the atmosphere, both as CO2 and as methane from bogs and seabed sediments. Lush subtropical forests grew in polar regions, and sea levels rose to 100m higher than today. It appears that an initial warming pulse triggered other warming processes. Many scientists warn that this historical event may be analogous to the present: the warming caused by human emissions could propel us towards a similar hothouse Earth.

Guardian.co.uk (To view links or images in this forum your post count must be 2 or greater. You currently have 0 posts.)

[Monte314]

So, the Summer Soltice is long past, and the Autumnal Equinox is approaching. Is the North Polar Ice Cap gone yet?

[Dave C C]

What about Piri Re'is map, we could still be living in an Ice Age.

[cncracer]

The global warming is bad news all around:
1- The salinity of the ocean will change and micro organisms and some larger organisms will not be able to adjust. These are the base of the marine food chain, and will lead to massive extinctions.
2- The melting of the polar caps will release more CO2 captured over millions of years and resulting in lower pH rain (Carbonic acid) the result will a change in pH in the oceans and will push another layer of organisms into the history books.
3- The sea level could rise as much as 20 to 40 feet. This will displace millions, and flood many major cities world wide.
4- The warmer water will produce stronger storms which will move slower. Higher sea levels, bigger storms and slow moving storms are relates to the triple crown for disaster.

The summary will be starvation, mass extinctions, bad storms, lost land masses, millions of homeless humans, collapsed social structure, economic stressed to the breaking point. I think the only gain will be shipping through the North West passage. I see it as a bad trade off.

[Monte314]

So, once again... did the polar ice caps melt this Summer?

I haven't heard another word about this... which is typical with alarmist drum-beating.

If the global warming crowd wants to retain their credibility, they are going to have to make sure their sensational claims continue to be too vague or distant in time to be subject to actual verification.

Looks like this one might be an "Oops!"... but, if it is, the mainstream media can be counted on to look the other way.

[enWTFp]

London is flooded. In the old Lord's mansion:
- Sir, may I...
- I told you not to interrupt. Leave me now.
Later.
- Sir, really I apologize, but...
- How many times to repeat!! Do not disturb me right now!
Finally, the door opens again:
- Thames, sir.


I do not think so much whether Global warming is false alarm or not, because it is not the only dangerous ecological effect produced by us. It's, if you like, just a simple way to let simple people know that something is happening without explaining in details. Like most of any published information.

[PHS Philip]

Well, Monte, to be fair, this was not mainstream climate scientists, from what I can see. It looks like the mainstream estimates give us at least 40-60 year. The mainstream media garble and mangle science stories, and often pick pretty fringe people for their stories.

[Monte314]

Waaaaah! I don't want to be fair...

But, it looks like you are right. They did get a lot of attention for a while there. If they were "mainstream" before, they probably aren't now!