[loz]

http://news.bbc.co.uk/1/hi/sci/tech/6944401.stm

The extent of sea ice has been declining over the past 30 years
Arctic sea ice is expected to retreat to a record low by the end of this summer, scientists have predicted.

Measurements made by the US National Snow and Ice Data Center (NSIDC) showed the extent of sea ice on 8 August was almost 30% below the long-term average.

Because the region's melting season runs until the middle of September, scientists believe this summer will end with the lowest ice cover on record.

Researchers have forecast ice-free summers in the Arctic by 2040.

Also nice little interactive map showing the size of the artic sea ice

[njp]

I've already posted this link elsewhere pretty much as an aside, but since we now have a thread on the subject...

Cryosphere Today (which sounds like a guest publication on HIGNFY!) has lots of graphs and considerably more impressive sea-ice animations (both Java and Quicktime) for both the northern and southern hemispheres.

Originally Posted by loz

http://news.bbc.co.uk/1/hi/sci/tech/6944401.stm



Also nice little interactive map showing the size of the artic sea ice

Don't forget Lewis Gordon Pugh, who swam 1 km at the (real) North Pole in July to publicise the reduction in Arctic ice. Note that I'm not claiming that his swim in itself proved anything. See here.

Originally Posted by njp

I've already posted this link elsewhere pretty much as an aside, but since we now have a thread on the subject...

Cryosphere Today (which sounds like a guest publication on HIGNFY!) has lots of graphs and considerably more impressive sea-ice animations (both Java and Quicktime) for both the northern and southern hemispheres.

Great site, thanks!

[Nimby]

Presumably the cryosphere is so-called because of the tears now being shed over its loss?

[Corey USA]

Another demonstration of the "record breakers" with the increase in frequency since recorded time. I was talking about this kind of record breakers in another thread related to weather from climate impacts.
while you were out NJP.

[Mr Incredible]

Interesting that in Al Gore's "An Inconvenient Truth" he floated ( pun intended) the hypothesis that the melting of floating ice did not affect the water level (he showed a photograph of ice in a glass before and after melting and the water level).

I know there was a study a couple of years ago which modelled the impact on the North Atlantic Drift by the introduction of vast quantities of fresh water through melting ice and how that affected densities and temperatures. But it appears that this model may not be as valid as first thought. A new study (reported in the New Scientist) suggests the change in the Atlantic currents is far quicker than first thought and the original study may have inadvertently drawn its conclusions from data which is within normal variability.

However back to MR Gore's hypothesis for a moment. For the scientifically minded (well mathematically), I have been pondering for years about the real world impact of a less dense (floating) object melting. Archimedes principal states that a floating body displaces water equivalent to its own mass. But as ice is fresh water and is less dense that sea water, floating ice displaces LESS volume of sea water than the volume of water in the floating ice. So to my mind the water level should rise by the ratio of relative densities of fresh water to salt water.

Oceans at the surface have a density of about 1027 kg/m3, and fresh water 1000 kg/m3. So in my books, the % increase should be (1027 - 1000)/1027*100 or 2.6% Not the: "water level does not change" stance of Al Gore.

And in case you think I am being too simplistic, then you are absolutely correct. There are many more factors at work, such as the relative temparatures and changes in density which occur at the surface.

So, it was a pleasant surprise to me to find that a couple of scientific bods had published a paper and had been peer reviewed, which showed the impact of melting ice caps (floating variety) on the sea level. You can read it here.

After pages and pages of calculations, assumptions, neat diagrams and not too difficult maths, they concluded that the metling of floating ice would raise the water level by an average of..................























2.6%



They should have come to me first I would have saved them a lot of time!!

Enjoy the read.

[Corey USA]

That big gap is that an accident or edited out?

[Mr Incredible]

Originally Posted by Corey USA

That big gap is that an accident or edited out?

I think in the performing arts it's known as a dramatic pause!!

It's like someone pausing to deliver a punch line!

It was an intentional gap!














Honest!

[Nimby]

Originally Posted by Mr Incredible

I think in the performing arts it's known as a dramatic pause!!

It's like someone pausing to deliver a punch line!

It was an intentional gap!



Honest!

Your pause for pathos gave us pause.

[pjclark1]

Originally Posted by Mr Incredible

However back to MR Gore's hypothesis for a moment. For the scientifically minded (well mathematically), I have been pondering for years about the real world impact of a less dense (floating) object melting. Archimedes principal states that a floating body displaces water equivalent to its own mass. But as ice is fresh water and is less dense that sea water, floating ice displaces LESS volume of sea water than the volume of water in the floating ice. So to my mind the water level should rise by the ratio of relative densities of fresh water to salt water.

Oceans at the surface have a density of about 1027 kg/m3, and fresh water 1000 kg/m3. So in my books, the % increase should be (1027 - 1000)/1027*100 or 2.6% Not the: "water level does not change" stance of Al Gore.

You need to take into account that ice is a very unusual substance ........ when it melts (gets warmer) it shrinks ........ just about the only substance that does this (else ice wouldn't float). It's about an 8% decrease when it melts, which means, if you compare your 2.6% salt factor to my 8% melt factor, melting the ice is likely to decrease the volume by about 5%, not an increase of 2.6% as you stated.

[Mr Incredible]

Originally Posted by pjclark1

You need to take into account that ice is a very unusual substance ........ when it melts (gets warmer) it shrinks ........ just about the only substance that does this (else ice wouldn't float).

My view is that using Archimedes' principal and the relative densities of salt water and fresh water, the fact that the fresh water was in a different phase (and hence lower density with higher volume for the same mass of water) and displacing the same mass of salt water whether ice, or melted water, is in IMHO irrelevant to the calculations.

[njp]

Originally Posted by pjclark1

You need to take into account that ice is a very unusual substance ........ when it melts (gets warmer) it shrinks ........ just about the only substance that does this (else ice wouldn't float). It's about an 8% decrease when it melts, which means, if you compare your 2.6% salt factor to my 8% melt factor, melting the ice is likely to decrease the volume by about 5%, not an increase of 2.6% as you stated.

That level of misunderstanding is actually quite tragic.

[Nimby]

Originally Posted by njp

That level of misunderstanding is actually quite tragic.

Play nice njp!

Or at least add a smiley to show humour.

Intellectual arrogance is always unsightly.

We can all thrash each other in our own fields of expertise.

Kindly do the "ignorant" the kindness of pointing out how you think something actually works.

It moves the discussion on and hopefully your contribution will sway a doubter and educate those who want to learn more.

Knowledge is power. Empower those who have none.

[Mr Incredible]

Originally Posted by pjclark1

It's about an 8% decrease when it melts, which means, if you compare your 2.6% salt factor to my 8% melt factor, melting the ice is likely to decrease the volume by about 5%, not an increase of 2.6% as you stated.

You added this between your first reply and me typing out my response. You'd have been better leaving it as it was!

An old phrase comes to mind: "Better to say nothing and appear ignorant than to open one's mouth and remove any doubt"!

[andykn]

Originally Posted by pjclark1

You need to take into account that ice is a very unusual substance ........ when it melts (gets warmer) it shrinks ........ just about the only substance that does this (else ice wouldn't float). It's about an 8% decrease when it melts, which means, if you compare your 2.6% salt factor to my 8% melt factor, melting the ice is likely to decrease the volume by about 5%, not an increase of 2.6% as you stated.

Yes, the total volume of ice decreases, but when it was solid, a lot of it was not in the water, but above it. Once it melts, it all goes in the water.

If you assume that about 10% of the ice is above water, say you have 1 cubic meter of ice, 0.1 cu m is above water, 0.9 cu m in the water. When it melts the 1 cu m turns in to 0.92 cu m of water, a 0.02 cu m increase on the 0.9 cu m originally in the water. 0.02 divided by 0.9 is a 2.2 % increase.

[pjclark1]

Originally Posted by njp

That level of misunderstanding is actually quite tragic.

Actually I was joking, as serious answers and debate are always deleted there is little point in making any.
Andykn knows exactly what I mean as a question he keeps asking, is deleted when I answer it in a serious way (cough Eugenics).

This (part of the) forum is such a joke you either laugh, or leave.
Even the mods get sacked for taking the wrong side!
Lets hope Nimby lasts a while as he seems really fair (in a pro AGW sort of way).

Real discussions where real people actually try to help the problem (if it exists) seem to happen in other areas of the site
SVO (veg oil from the shelf:)) As fuel...

[Mr Incredible]

Just an interesting observation about the published study:

They experimented and did calculations assuming the floating ice was of the same composition that one would get from ice formed in glaciers, i.e from "fresh water". However, sea ice forms at lower temperatures than fresh water ice and is actually denser than fresh water ice and therefore does not float as "high". As a result I believe the % increase in the level is much less than that which was reported. But that's splitting hairs anyway as the 2.6% rise relates to about 4cm IF ALL the sea ice melted, which I gather is unlikely to happen at any stage.

[Nimby]

Originally Posted by pjclark1

Actually I was joking, as serious answers and debate are always deleted there is little point in making any.

Generalisations do not become you.

[pjclark1]

Originally Posted by Nimby

Generalisations do not become you.

I stand corrected, please replace "always" with "often" (or sometimes)

[Mr Incredible]

And they say a picture paints a thousand words:-

[Corey USA]

Originally Posted by Mr Incredible

I think in the performing arts it's known as a dramatic pause!!

Honest!

[Mr Incredible]

The added heat from MMGW must have got to your brain Corey!!

[Corey USA]

Originally Posted by Mr Incredible

And they say a picture paints a thousand words:-

Where is the frozen fresh water ice from the continents of Greenland and Antarctica in this diagram?? Don't forget to add it. For if you take into account with the link I provided to monobiot's article for Ice sensitivity to Little temp changes which will makes a sudden change from solid to liquid then further expansion as it is heated due to the ice no longer reflecting the suns rays back into space..

Maybe make it more complete on how much water expands related to its temperature.

[Mr Incredible]

As both the topic and the published paper was only dealing with floating ice, and given that I haven't a clue about the volume of glacial ice etc, keeping it 100% OT was a sensible approach for me!

I agree with your last ccomment as I did some basic calcs a few years ago which showed for an average temp rise of a couple degrees in the whole volume of the earths oceans would raise sea levels by a phenomenal amount (can't remember the exact figure), and I remember thinking at the time that that was probably a greater threat than all the melting ice put together!