Why Do Melting Antarctic Ice Caps Cause Sea Levels to Rise?

[Buckleymanor]

No, you're wrong. They wouldn't lower the temperature to anything we could ever measure.


Wrong yet again because I didn't say that. What I said was that Archimedes principle doesn't have anything to do with how temperature affects density which your post said it did. And your post was (what else?) wrong.

So you're still wrong no matter how much you try.

Better leave it to Mr Right.

 

[paisiello2]

Better leave it to the facts.

 

[D H]

Better leave it to the facts.

Buckleymanor, you are wrong.

The fact is that ice floats because it is less dense than water. Measure the volume of a chunk of ice, melt it, and measure the volume of the water. The volume of the melt will be less than the volume of the chunk of ice.

The density of liquid water does vary with temperature, reaching a maximum at some above point where water (how much above varies with salinity), but this variation is small compared to the much larger difference in density between liquid water and ice.
This sidetrack has left a key question raised in the original post unanswered.

And if so, why do people say melting antartic ice caps cause sea levels to rise? Wouldn't the ice simply melt and occupy the same volume as the frozen portion which is below the surface therefore sea levels would remain exactly the same?

Consider two experiments involving melting ice surrounded by water. The goal is to determine whether the level of the level of the water rises, falls, or remains the same.

In experiment #1 we'll float a chunk of ice in some water. We'll measure the level of the water immediately after adding that chunk of ice, and then later when the ice has melted. Except for small variations due to the fact that the density of water varies with temperature, the level of the water will remain pretty much the same.

In experiment #2 we'll first put a big rock in the water, with the rock big enough so that the top pokes out of the water. Then we'll put our chunk of ice on top of the rock. Once again, we'll measure the level of the water immediately after adding that chunk of ice, and then later when the ice has melted. Now the water level will indeed rise.

Experiment #1: That represents the sea level rise that would result from the ice in the Arctic melting (not much). Experiment #2: That represents the sea level rise that would result if the ice in the Antarctic melts (a considerable rise).

The Arctic is an ocean covered with floating sea ice during the winter. Antarctica is a continent, a big rock whose top sits above sea level. Note also that the ice covering Greenland isn't floating. Melting the ice covering Greenland would similarly contribute to a rise in sea level.

 

[jbriggs444]

Then we'll put our chunk of ice on top of the water.

I think you intended to put your second chunk of ice on top of the rock.

 

[D H]

I think you intended to put your second chunk of ice on top of the rock.

Indeed I did. Thanks. I fixed my post.

 

[paisiello2]

This sidetrack has left a key question raised in the original post unanswered.

I believe it was all answered in post #2.

 

[Buckleymanor]

Buckleymanor, you are wrong.




Consider two experiments involving melting ice surrounded by water. The goal is to determine whether the level of the level of the water rises, falls, or remains the same.

In experiment #1 we'll float a chunk of ice in some water. We'll measure the level of the water immediately after adding that chunk of ice, and then later when the ice has melted. Except for small variations due to the fact that the density of water varies with temperature, the level of the water will remain pretty much the same.

In experiment #2 we'll first put a big rock in the water, with the rock big enough so that the top pokes out of the water. Then we'll put our chunk of ice on top of the rock. Once again, we'll measure the level of the water immediately after adding that chunk of ice, and then later when the ice has melted. Now the water level will indeed rise.

Experiment #1: That represents the sea level rise that would result from the ice in the Arctic melting (not much). Experiment #2: That represents the sea level rise that would result if the ice in the Antarctic melts (a considerable rise).

The Arctic is an ocean covered with floating sea ice during the winter. Antarctica is a continent, a big rock whose top sits above sea level. Note also that the ice covering Greenland isn't floating. Melting the ice covering Greenland would similarly contribute to a rise in sea level.

Experiment 1 and 2 are representative of what happens over a long period of melting . For these events to happen the temperature would have to increase by a substantial amount.As mentioned the seas would contract before any melting of the Antarctic cap.
The Antarctic cap is surrounded by sea ice which would first have to melt before the ice cap thawed causing an increase in sea density.
Additional to that the Arctic cap melts and recovers at a faster rate than the Antartic cap.
This melting of the Antarctic sea ice, the Arctic cap and sea will lower the temperature of the seas and increase density.
So unless the laws of physics have changed the seas will contract before there is any thermal expansion and the Antarctic ice cap melts.

 

[D H]

When sea water freezes (around -2 degrees) the salinity remains in the ice, it does not fall out of the solution.

Minor correction: The salinity does drop out of the solution. However, freshly frozen sea ice remains rather salty because as the ice forms, the salt forms pockets of liquid brine (extremely salty water) that are intermixed with the solid ice.

Now it's churlish to say the least to use Archimedes to support your argument with regards ice which only floats because lowering the temperature of water causes it to expand and become a floating partly submerged body.

Major correction: This is completely wrong, and it is the source of your confusion. Ice floats because it is considerably less dense than water. The density of liquid water (pure, not salty) at 0° C is 0.9998 g/cm³, or 0.02% less than the density of water at 4° C. The density of ice at 0° C is 0.9162 g/cm³, or 8.36% less than the density of water at 0° C.

You are making a mountain of the tiny molehill of variations in density of liquid water as a function of temperature and are at the same time ignoring the huge mountain that represents the significant difference in density between liquid water and solid ice.

The Antarctic cap is surrounded by sea ice which would first have to melt before the ice cap thawed causing an increase in sea density.

This is false as well. The ice cap is melting *now*. This has been verified by satellites such as GRACE. The volume of land ice on the Antarctic continent is falling. Some of that melt enters the seas that surround Antarctic as liquid water, but a whole lot more enters those seas as ice from glaciers flowing from the Antarctic plateaus and mountains into the sea.

 

[Buckleymanor]

This is false as well. The ice cap is melting *now*. This has been verified by satellites such as GRACE. The volume of land ice on the Antarctic continent is falling. Some of that melt enters the seas that surround Antarctic as liquid water, but a whole lot more enters those seas as ice from glaciers flowing from the Antarctic plateaus and mountains into the sea.

Not according to NASA
http://wattsupwiththat.com/2013/10/22/nasa-announces-new-record-growth-of-antarctic-sea-ice-extent/
The point was that the Arctic sea ice old and new will melt first before the Antarctic sea ice and cap. Thus lowering the mean temperature of the sea and it's density before the main bulk of land ice on the Antarctic melts. We will fry before any substantial sea levell rise.

 

[russ_watters]

Not according to NASA
http://wattsupwiththat.com/2013/10/22/nasa-announces-new-record-growth-of-antarctic-sea-ice-extent/

That link is clearly about sea ice, not land ice.

The point was that the Arctic sea ice old and new will melt first before the Antarctic sea ice and cap.

The link you posted also explicitly states that the cap itself is melting.

Thus lowering the mean temperature of the sea and it's density before the main bulk of land ice on the Antarctic melts. We will fry before any substantial sea levell rise.

HOW MUCH?

The volumes of the oceans and ice can easily be found with a Google. Assuming it could be done adiabatically(which it can't), this is a simple mixing problem with a thermal contraction. You should be able to show the math behind your claim.

(Edit) Hint: I just did the math and the impact of the temperature change falls out as a rounding error if you don't keep enough sig figs.

 

[Buckleymanor]

Major correction: This is completely wrong, and it is the source of your confusion. Ice floats because it is considerably less dense than water. The density of liquid water (pure, not salty) at 0° C is 0.9998 g/cm³, or 0.02% less than the density of water at 4° C. The density of ice at 0° C is 0.9162 g/cm³, or 8.36% less than the density of water at 0° C.

You are making a mountain of the tiny molehill of variations in density of liquid water as a function of temperature and are at the same time ignoring the huge mountain that represents the significant difference in density between liquid water and solid ice.

Ice does not have to be considerably less dense than water to float it just happens to be so.
Like wise water at 4 degrees is denser than water at 0 degrees and is only marginaly denser.
That won't stop it from sinking and occupying less space than warmer water.
The average temperature of the sea is 3.5 degrees C so any additional cooling or warming causes thermal contraction or expansion.

 

[russ_watters]

the average temperature of the sea is 3.5 degrees c so any additional cooling or warming causes thermal contraction or expansion.

How much?

 

[Buckleymanor]

How much?

That depends on depth and the rise in temperature on the land. For every degree of temperature rise on land it will translate to about 0.2 degree temperature rise in the sea but only to a certain depth say 25 meters.That will result in the expansion of the oceans by around 2.5 millimeters in hight.

 

[russ_watters]

That depends on depth and the rise in temperature on the land. For every degree of temperature rise on land it will translate to about 0.2 degree temperature rise in the sea but only to a certain depth say 25 meters.That will result in the expansion of the oceans by around 2.5 millimeters in hight.

That's not the totality of your claim. You claimed that the melting of the ice caps would lower the sea level, not raise it. Please show us the calculation that supports your claim.

 

[Buckleymanor]

That's not the totality of your claim. You claimed that the melting of the ice caps would lower the sea level, not raise it. Please show us the calculation that supports your claim.

Only to the point of floating ice if the presumption is that the Arctic cap and sea ice melts first and then the sea ice in the Antarctic melts before the main cap (which it probably will).
Land ice melt in the main Antarctic cap will eventualy raise the sea level though until that happens the sea level would lower.
Fresh melting sea ice at 0 degrees would mix with warmer water at whatever temperature, the result would be that the warmer water will end up cooler than it's original temperature.
Sea water becomes more and more dense right down to it's freezing point so the result would be a more dense and lower sea.

 

[russ_watters]

Only to the point of floating ice if the presumption is that the Arctic cap and sea ice melts first and then the sea ice in the Antarctic melts before the main cap (which it probably will).

Your own link says that that isn't what is happening. You're running close to this being misinformation. But if you want to do it that way, calculate how much the sea level rises or falls if all of it melts.

Land ice melt in the main Antarctic cap will eventualy raise the sea level though until that happens the sea level would lower.
Fresh melting sea ice at 0 degrees would mix with warmer water at whatever temperature, the result would be that the warmer water will end up cooler than it's original temperature.
Sea water becomes more and more dense right down to it's freezing point so the result would be a more dense and lower sea.

Stop claiming it and prove it!

In case you forgot, this was your claim:

Ice sheets and ice caps melting lowers the temperature of sea water makeing it more dense this in turn lowers the volume of water within the oceans unless Archimedes was wrong.

So do the calculation: calculate what the resulting change in ocean volume will be if all of the ice sheets and caps melt and the temperature drops adiabatically. We know this can't happen since the ice melting is caused by the temperature rising, but I want you do do the math that shows that even with your wrong assumption helping you out, your conclusion is still wrong.

Maybe it is still possible for you to learn something here rather than just trot-out wrong claim after wrong claim.

 

[craigi]

Only to the point of floating ice if the presumption is that the Arctic cap and sea ice melts first and then the sea ice in the Antarctic melts before the main cap (which it probably will).
Land ice melt in the main Antarctic cap will eventualy raise the sea level though until that happens the sea level would lower.
Fresh melting sea ice at 0 degrees would mix with warmer water at whatever temperature, the result would be that the warmer water will end up cooler than it's original temperature.
Sea water becomes more and more dense right down to it's freezing point so the result would be a more dense and lower sea.

Some important points, but not an exclusive list, that you're missing in your argument:

* Land ice is already melting. The rate is enormous. I won't discuss this here due to forum rules, but you can search for "Greenland Ice Melt".
* Heat transfer does not only take place through the movement of liquid water.
* Sea ice melts because of an increase in water temperature.
* Sea ice absorbs radiation much more than sea water

 

[russ_watters]

Question is asked and answered and the thread is now going nowhere so it is locked.