Enthalpy of fusion - missing factor in climate change?

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Dorrian's picture
Dorrian
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Joined: Sep 15 2009
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Enthalpy of fusion - missing factor in climate change?

Hi everybody,

There is a very interesting blog entry about the melting of the arctic ice on Heise Telepolis, one of Germany's biggest technology news sites (comparable to "Slashdot" in the U.S.). For those of you who are capable of reading German texts, the article can be found here.

For all others I will summarize the article in my own words, for I could not find a similar article in english.

There is a physical phenomenon called "Enthalpy of fusion". It describes the amount of energy that is required to change the state of a substance.

If you had 1 kg of frozen water ("ice") at 0° Celsius and wanted to turn that into 1 kg of liquid water at 0° Celsius, you had to use 334 KJ. The water stays exactly at the same temperature (0° Celsius), it just changes its state from ice to liquid.

If you have no clue about what "334 KJ" means: This amount of energy can be used to heat up 1 kg liquid water from 1° to 80° Celsius.

This phenomenon explains, why snow lays around so long in springtime, though temperatures have risen quite much: It takes immense amounts of energy to change the state of the snow.

People, and even scientists, often forget about the enthalpy of fusion. Once the arcitc sea ice is melted in summer (which will occur approximately in 10 to 20 years at the latest), things will speed up dramatically.

And by the way, the poles of the earth have been ice-free for ca. 90% of all the earth's history. You can consider "ice-free poles" as the "normal state" of the earth. The reason the poles are iced at this time is that we are at the end of a longer period of coldness.

It will take maybe another few thousand years, but at one day in the future even the antarctic continent may be ice-free. Our human influence speeds this up, but I don't think anyone of us will ever witness that with his/her own eyes. :-)

Have a nice day

Dorrian

 

Dogs_In_A_Pile's picture
Dogs_In_A_Pile
Status: Martenson Brigade Member (Offline)
Joined: Jan 4 2009
Posts: 2606
Re: Enthalpy of fusion - missing factor in climate change?
Dorrian wrote:

This phenomenon explains, why snow lays around so long in springtime, though temperatures have risen quite much: It takes immense amounts of energy to change the state of the snow.

People, and even scientists, often forget about the enthalpy of fusion. Once the arcitc sea ice is melted in summer (which will occur approximately in 10 to 20 years at the latest), things will speed up dramatically.

Dorrian -

I'd have to break out my old Thermo texts, but I think there is a lot of sensible heat that will need to get transferred after the sea ice melts before the train gets rolling.  Latent heat flowing out of the Arctic/Antarctic will have a mitigating influence on sensible heat transfer to the polar regions.

Don't forget, in our atmosphere, sensible heat is transferred from tropics to poles and latenty heat is transferred from poles to tropics via air circulation driven by cyclonic mixing in the middle latitudes.  So there are any number of parametric variables in your scenario. 

I'll defer to the meteorologists and WEAX guessers in the crowd (Aaron) for a detailed discussion on Ferrel cells.

Mike Pilat's picture
Mike Pilat
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Joined: Sep 8 2008
Posts: 929
Re: Enthalpy of fusion - missing factor in climate change?

This isn't simply an enthalpy issue. The albedo of the ice is something like 4 times that of water...So losing ice caps is a positive feedback mechanism in terms of the amount of energy the earth absorbs.

That said, I've heard that arctic sea ice has actually experienced some very significant increases lately as a result of this cold winter. Apparently it has been the coldest in 28 years and it certainly feels it (18 degrees this morning in DC Spin Zone). We also had our biggest snowfall in 24 hours in 70+ years, I believe. Look at energy and citrus prices too...this global freeze up has caught many by surprise.

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