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#56325 - 29/01/2003 08:28 Do you agree or disagree
adam17 Offline
Weatherzone Addict

Registered: 13/01/2002
Posts: 3268
Loc: Townsville - Queensland
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#56326 - 29/01/2003 09:29 Re: Do you agree or disagree
Harry Spotter Offline
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Registered: 14/11/2001
Posts: 1955
Loc: Springwood, Brisbane
Interesting, Adam. I like the idea that a warmer climate would also increase evaporation. Also, if the sections of the ice caps BELOW sea level melt (where the majority of the ice caps lie), oceans would actually drop as frozen water (ice) takes up more space than liquid water.

Marty.
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#56327 - 29/01/2003 10:05 Re: Do you agree or disagree
flip Offline
Weatherzone Addict

Registered: 27/12/2001
Posts: 2536
Loc: Concord, Sydney
Its certainly more believable and makes more common sense then all this other doomsday rubbish. wink

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#56328 - 29/01/2003 10:11 Re: Do you agree or disagree
Danos Offline
Weather Freak

Registered: 06/12/2002
Posts: 934
Loc: Deception Bay
Quote:
Originally posted by Harry Spotter:
Also, if the sections of the ice caps BELOW sea level melt (where the majority of the ice caps lie), oceans would actually drop as frozen water (ice) takes up more space than liquid water.
That is a very interesting point! I do not agree though with the mention about the rivers pouring billions of litres into the oceans with no effect, because all this current water is part of the current cycle, adding more water to it (ie - melting ice of the polar caps above sea level) will definately cause some kind of rise in level, but I doubt to the sensationalism of some 'scientists'.

Also, if added heat was to cause more evaporation which would keep the levels pretty much the same, would this mean it would rain more often? Or am I way off the mark there? laugh

-Armishdan

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#56329 - 29/01/2003 10:19 Re: Do you agree or disagree
Anthony Cornelius Offline
Meteorologist

Registered: 22/05/2001
Posts: 5162
Loc: Brisbane
Hi all,

Keep in mind that it is a known fact that sea levels do rise/fall - ie during ice ages the sea level drops because much of it becomes trapped in ice.

In regards to not being able to measure sea level, a lot of careful study is done into compensating for tides so that this is removed from the equation. A long term average is taken to determine the height of sea level at one particular area. But this is done across the world, and if across the world the sea level has risen a small amount then one could certainly have evidence to suggest that the sea level overall has risen slightly.

Also, a few interesting points of note...

Oceans contain 97% of all water, if you spread this across the entire Earth the depth would be ~2.65km

Next, ice caps have 2.2% of all water (second largest storage base), if you spread this across the entire Earth the depth would be ~60m, which is quite considerable.

Ground water has 0.7% of all water I believe, which isn't much - but when you compare it to rivers, lakes etc that only contain 0.013%, you begin to appreciate just how little rivers impact on the ocean. In fact, if you emptied all of the rivers and lakes across the world, the depth of the water would only be around 35cm! So if one river floods and pours water in the ocean, you can see how small this is in comparison to the overall scheme of things. Hence why the ocean doesn't "flood" from heavy rain. But you can also see how much more of an effect ice caps have the potential to increase the sea level then other factors.

So I guess you could say I disagree with what he says smile

AC

(PS shouldn't this be in general weather?)
_________________________
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#56330 - 29/01/2003 10:25 Re: Do you agree or disagree
Adiabatic Offline
Member

Registered: 01/09/2001
Posts: 14190
Loc: Knoxfield 96m: 120.2mm
Your the moderator AC up to you smile

Good article, and a good post AC, learnt something new today smile

Karl smile

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#56331 - 29/01/2003 10:45 Re: Do you agree or disagree
bogong Offline
Weatherzone Addict

Registered: 05/10/2001
Posts: 1398
Loc: Canberra ACT (Higgins - NW Can...
If sea levels can never rise, then how come there are drowned river and glacial valleys all over the world?

There are fjords in Norway and New Zealand. Sydney Harbour and Port Phillip Bays are drowned river valleys - the old river beds are still identifiable by geologists (as are old river beds on the former Bass Strait peninsular that used to join Tasmania to the mainland).

In terms of sea level rise, one of the major contributors is actually the increase in volume of the water as its temperature increases. This same principle that liquid thermometers use to measure temperature - as the temperature rises, the volume expands. A thermometer measures the change in volume (which is a result of the change in temperature).

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#56332 - 29/01/2003 10:48 Re: Do you agree or disagree
Danos Offline
Weather Freak

Registered: 06/12/2002
Posts: 934
Loc: Deception Bay
I was once told that the deserts in the center of australia were once an inland sea, and that ayres rock was an island of some sort.

I think that person was taking the **** but if not Id like to know how long ago that actually was. Many millions of years i would guess.

-Armishdan

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#56333 - 29/01/2003 11:02 Re: Do you agree or disagree
Stormspell Offline
Member

Registered: 08/01/2003
Posts: 130
Loc: Brisbane
Hi Everyone,Someone told me that as well about the centre of australia but can't remember the source now.

ANyway, just another point. If as they say in the article that more evaporation would be casued by raised sea levels, this would increase the temperatures as well wouldn't it as I read in one of these interesting threads that water vapour is actually the most efficient greenhouse gas for trapping heat. That would in turn melt more ice, raise sea levels again and cause more evaporation, raise the remperature further until what? Will this keep going until there is no ice left?

SS

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#56334 - 29/01/2003 12:30 Re: Do you agree or disagree
Fine Elsewhere Offline
Weatherzone Addict

Registered: 02/09/2002
Posts: 1877
Loc: Albany.W.A.
Thanxs Adam18 for a great thread, thanx AC for some VERY interesting data on where water is on the earth!!! that has really made me think & better undersatnd this whole water level thing...i must read some more now before i comment further..great site WZ - always learning!!
:cheers: FE

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#56335 - 29/01/2003 12:43 Re: Do you agree or disagree
W W Offline
Member

Registered: 09/01/2002
Posts: 1227
Loc: Cobar 31.50S, 145.83E, 243m ...
Thanks that was very interesting to read & think about

Heather

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#56336 - 29/01/2003 14:16 Re: Do you agree or disagree
Rbl Offline
Member

Registered: 09/06/2001
Posts: 204
Loc: Wagga, NSW, Australia
Hi all,

Just a little "off topic" here I guess, but in relation to the %ages of water on the globe in it's various states and the "water cycle" in general, consider this. The watre cycle is an infinite cycle....in general very little if any water is added to or taken away from the system. So...that means that the water you drink today, had to come from... somewhere else...just think about that for a min, and you might get my drift!!

Finally, a little statistic that may interest some of you...1mm of rain = 1 litre/square meter ...so a 10mm shower produces quite a lot of water.

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#56337 - 29/01/2003 14:35 Re: Do you agree or disagree
adam17 Offline
Weatherzone Addict

Registered: 13/01/2002
Posts: 3268
Loc: Townsville - Queensland
1mm of rain = 1litre per Sq Metre.
Interesting concept.
Assuming 1 litre is 10x10x10cm. Which is equal to 1000cm. 1 Metre squared consists of 100x100x100cm = 1000000cm so. 1000000/ 1000 = 1000 litres per square meter. So Im guessing 1000mm of rain.. would be enough to fill a 1x1x1 open top cube. (sorry If i am looking stupid here. Its been about 2 months since I last touched a calculator.)

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#56338 - 29/01/2003 14:36 Re: Do you agree or disagree
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
Quote:
Originally posted by Harry Spotter:
Also, if the sections of the ice caps BELOW sea level melt (where the majority of the ice caps lie),
Actually, most of the Antartic ice cap is sitting on a land mass and hence above the current mean sea level. Melting of the Antarctic ice cap is therefore a big concern for low-lying land areas. Antarcica is called a continent for a reason wink

As for being able to measure sea level differences - quite easily done. As AC said, the tides, swell and such can be taken out easily. The height of the sea level is a very dynamic feature of the oceans, even without the tides. Variations in sea level height are one of the main driving forces of ocean currents. A 10 cm difference in the height of the sea surface is enough to drive a significant current.

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#56339 - 29/01/2003 14:43 Re: Do you agree or disagree
flip Offline
Weatherzone Addict

Registered: 27/12/2001
Posts: 2536
Loc: Concord, Sydney
Quote:
Originally posted by Stormspell:
Hi Everyone,Someone told me that as well about the centre of australia but can't remember the source now.

ANyway, just another point. If as they say in the article that more evaporation would be casued by raised sea levels, this would increase the temperatures as well wouldn't it as I read in one of these interesting threads that water vapour is actually the most efficient greenhouse gas for trapping heat. That would in turn melt more ice, raise sea levels again and cause more evaporation, raise the remperature further until what? Will this keep going until there is no ice left?

SS
The atmosphere can only hold so much moisture before it condenses and precipitates which cools things down again smile Plus cloud cover prevents the ground heating.

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#56340 - 29/01/2003 14:52 Re: Do you agree or disagree
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
Flip, your second point is more critical. Less solar radiation reaching the ground means less heating, hence less evaporation. This means less moisture to condense as cloud so less cloud so more solar radiation to heat the surface so more evaporation so more atmospheric water vapour so more cloud so less solar radiation... wink

It all evens out in the end to reach a happy balance (that we now have). When you start dumping more 'greenhouse gases' into the atmosphere, it upsets the natural balance and so leads to a warming trend - the hyped-up greenie's 'Greenhouse Effect'.

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#56341 - 29/01/2003 16:15 Re: Do you agree or disagree
Fine Elsewhere Offline
Weatherzone Addict

Registered: 02/09/2002
Posts: 1877
Loc: Albany.W.A.
Now am i showing my total ignorance in matters scientific here, but with the accountablity of where the earths water is (ie % in ocean, rivers ground water etc) can there be some calculation of the mean average (in % terms)of water (vapour)that is in the atmosphere? When i look at the annual rainfall for equatorial regions, (or even the inches of rain that fell in nth west last week, or any other cyclone)there must be huge volumes of water constantly in the atmosphere (going up or coming down)...would this equate to any % or is it an unmeasurable or too insignificant to measure?
:cheers: FE

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#56342 - 29/01/2003 23:19 Re: Do you agree or disagree
adam17 Offline
Weatherzone Addict

Registered: 13/01/2002
Posts: 3268
Loc: Townsville - Queensland
I had forwarded the comments on to Bruce, he has replied.. As quoted
Quote:
Put an ice block into a nearly full glass of water measure the water level and then wait for the ice to melt and measure the water level again and you will find that the water level is exactly the same, therefore melting ice over the Arctic would neither lower or raise the sea levels. Every Arctic, and Antarctic summer the pack ice-floes all break up and melt and the glaciers calve their gigantic icebergs which all float around and eventually melt, this takes place every year with no rising of sea levels the same events takes place in the Arctic waters in its respective summers with the same result no rise or lowering of sea levels, and as summer gives place to winter and once again everything freezes over. Note that the worlds largest iceberg was found in 1956 and measured over 31,000 square k (12,000 square miles) making it about the same size in area as the country of Belgium. AND YOU CAN REST ASSURED THAT WHEN THIS VERY LARGE ICEBERG FINALLY MELTED IT HAD NOT RAISED THE OCEANS ONE LITTLE BIT. Nor can all and I mean all of the worlds rivers discharge raise the oceans for if these polar ice and river waters combined was ever going to raise the oceans levels it would have done so many years ago. There are those who claim that, and its mentioned below that water-sea levels dropped during the ice age, and as I have already proved all ice flows and remember that more than 90 percent of the Arctic ice is already resting over water and the sea levels have never ever got lower or higher because of freezing or thawing of this ice system. Note also that even if the Antarctic is resting on land more ice, more ice flows-packice icebergs are created here and there has ever since man first explored this vast continent the amount of ice has remained constant, in other words it is neither diminishing by the supposed global warming, nor is it increasing in size and area. Regards Bruce.

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#56343 - 30/01/2003 00:06 Re: Do you agree or disagree
Fine Elsewhere Offline
Weatherzone Addict

Registered: 02/09/2002
Posts: 1877
Loc: Albany.W.A.
Hi Adam18, Now i'm getting even more confused, remembering that AC said that in times of an Ice Age the sea level falls - is the chap who wrote the article saying the level remains the same regardless of whether the water is frozen or not? I note that when you fill a plastic bottle (only cos glass will break)& freeze - the ice pushes out of the bottle - ie there is no more water, its just that at freezing point water expands, as it melts the ice contracts and the bottle returns to being full. So again i'll ask a dumb question, do we actually have a fluctuation of more or less water ( & watervapour) in the earths atmosphere,oceans & land happening all the time or is it just a matter of redistribution of water to & from the poles?? confused
FE

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#56344 - 30/01/2003 00:36 Re: Do you agree or disagree
Overshoot Offline
Member

Registered: 19/08/2001
Posts: 2158
Loc: Wahroonga, North Shore, Sydney
Quote:
Originally posted by Craig Arthur:
Actually, most of the Antartic ice cap is sitting on a land mass and hence above the current mean sea level.
Hasn't the weight of the ice pushed much of the continent below sea level (and hence a fair bit of the ice too)? Like with Greenland I think. That'd still make your comment correct, but I'm just wondering how much there would be sitting above sea level (there are a few big mountains though). smile

Maybe we can just expect smaller tidal ranges? Like in Sydney, instead of 0m to 2m, they'd become 0.5m to 1.5m? This would be an extreme scenario obviously. smile If the melting of the ice doesn't actually increase the sea level, I would think it would make the tidal ranges smaller. Why? Because there is more 'liquid' in the ocean, which weighs more than the previous amount of 'liquid' and is hence more resistant to movement (has more inertia). I think this because I don't think icebergs have a lot of involvement in the tides at present because of their location near the poles (where no one notices the tides too much beause it's all frozen). They are just as involved as any parcel of water that is their mass, but if they melt, I am hypothesising a decrease in the tidal range away from the poles. Does anyone follow me? (even if you disagree with me?). smile

I'm off to bed! smile

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