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Ancient Rome's fish pens confirm sea-level fears
New Scientist ^ | 09:30 16 August 04 | Jeff Hecht

Posted on 08/16/2004 5:06:16 AM PDT by ckilmer

Ancient Rome's fish pens confirm sea-level fears

09:30 16 August 04

Exclusive from New Scientist Print Edition. Subscribe and get 4 free issues.

Coastal fish pens built by the Romans have unexpectedly provided the most accurate record so far of changes in sea level over the past 2000 years. It appears that nearly all the rise in sea level since Roman times has happened in the past 100 years, and is most likely the result of human activity.

Sea-level change is a measure of the relative movement between land and sea surfaces. Tide-gauge records show that the sea level has been rising 1 to 2 millimetres a year since widespread measurements began around 1900, but do not pinpoint when the trend started.

Earlier sea levels can be estimated from geological data, but the accuracy is limited to about half a metre, which is not enough to precisely chart the history of sea-level rise.

So Kurt Lambeck of the Australian National University in Canberra turned to fish pens on the Tyrrhenian coast of Italy for a more accurate record of ancient sea level.

Ice age rebound

The Romans dug these fish pens into bedrock, and the water line in these well-preserved structures shows that the sea level along the Italian coast 2000 years ago was 1.35 metres below today's levels. "They were used for only a very short time, so they make rather nice markers," says Lambeck.

He then analysed how land elevations changed along the Italian coast due to both plate tectonics and the after-effects of the last ice age. In a paper to appear in the journal Earth and Planetary Science Letters, he concludes that geological processes pushed the land up by 1.22 metres over last two millennia, which means that the global sea level rose by 13 centimetres.

That is only about 100 years' worth of rise at the present rate of around 1 to 2 millimetres per year, implying that nearly all of it has occurred since 1900. While there is no proof that human activity is to blame, "I can't think of a natural process that would have started in 1900," he says.

The result "is a significant one", says Jonathan Gregory, who studies global changes in sea level at the University of Reading, UK. The finding supports the idea, based on the few tide-gauge records that extend back two centuries, that the rise in sea level did indeed accelerate about a century ago.

While Gregory cautions that this does not prove that global warming is responsible, both he and Lambeck agree that the results fit the rise in ocean volume expected from global warming melting glaciers in the industrial age.

Jeff Hecht


TOPICS: Culture/Society
KEYWORDS: ancientrome; archaeology; babylon; catastrophism; climate; climatechange; eclipse; fagan; fishpen; ggg; globalwarming; globalwarminghoax; godsgravesglyphs; history; junkscience; politics; roman; romanempire; sealevel; shitforbrains; stalagmites
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To: Sci Fi Guy
Actually, there was just a major article out on Venice - it was in Discover or Smithsonian or one of those glossy mags.

There are multiple reasons for Venice's subsidence, none of which have anything to do with global warming. It's not the harbor that was dredged, but the ship channels through the nearby lagoon to the mainland. But the effect has been to increase the tidal action. The lagoon has also been partially filled, which prevents the marshy land from absorbing the tidal changes. The smaller canals in Venice have not been maintained, which causes water to bottleneck and erode buildings. Finally, both the city and the industrial areas on the nearby mainland have been pumping artesian water out of the ground in quantity. A change to aqueduct water appears to have stopped the ground subsidence due to removal of groundwater . . . but not enough.

It's a messy and complicated problem. The main thrust of the article was that people have known something needed to be done for at least 50 years, but the fabled inertia of Italian government has prevented most action.

61 posted on 08/16/2004 12:30:13 PM PDT by AnAmericanMother (. . . Ministrix of ye Chace (recess appointment), TTGC Ladies' Auxiliary . . .)
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To: ckilmer
The coastline of Italy is a completely unreliable indicator of sea level changes.

What was the primary Roman military harbor on the Adriatic coast at Ravena is now a city park, as the sea level has fallen so far that is is dry land.
Up the Adriatic coast at Venice, the city is drowning as the sea level rises.

The fact is that the land of Italy is tectonically active and slowly heaving up and down relative to the sea.

So9

62 posted on 08/16/2004 12:58:22 PM PDT by Servant of the 9 (Screwing the Inscrutable or is it Scruting the Inscrewable?)
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To: ckilmer

So 4ft in 2000 years.

I live 700 ft above sea level. Guess I'm ok.


63 posted on 08/16/2004 1:02:55 PM PDT by Mikey_1962
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To: sergeantdave

if the crust was pushed up, surely it could have as well fallen. i mean, the guy DID say its on a fault line, yes? the only things we know are things we can see. speculation is just that.

btw, i understand in 1900 the US and Britain and parts of Germany had industrialized..... the rate they are talking more or less says by next week we'll all be wearing wading boots.


64 posted on 08/16/2004 1:16:27 PM PDT by MacDorcha
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To: aruanan

Yeah, ice core taken in Antarctica showed (by proxy data) the climate trends, and the warming preceded the CO2 rise by a thousand years or so, each and every time. That figures -- CO2 increased because of biological activity, including the rot of stuff that had been frozen and buried. :')


65 posted on 08/16/2004 5:54:20 PM PDT by SunkenCiv (Unlike some people, I have a profile. Okay, maybe it's a little large...)
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To: ckilmer; abbi_normal_2; Ace2U; adam_az; Alamo-Girl; Alas; alfons; alphadog; amom; AndreaZingg; ...
Rights, farms, environment ping.
Let me know if you wish to be added or removed from this list.
I don't get offended if you want to be removed.
66 posted on 08/16/2004 8:30:46 PM PDT by farmfriend ( In Essentials, Unity...In Non-Essentials, Liberty...In All Things, Charity.)
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To: ckilmer
... the results fit the rise in ocean volume expected from global warming melting glaciers in the industrial age.

Excuse me, Professor ==

Just what was the name of that period during the last Ice Age?

Well, son, that was Global Cooling.

Ah. And then what was that period between the last Ice Age and the previous one?

That was also Global Warming, son.

Golly; who knew? Cavemen had an Industrial Age! Was that the first 'Wonder of the World?

Tasmanian Sea Levels: The `Isle of the Dead' Revisited ^

67 posted on 08/16/2004 9:36:50 PM PDT by brityank (The more I learn about the Constitution, the more I realise this Government is UNconstitutional.)
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To: ckilmer

The solution for lowereing the sea level is quite simple. Take all your measurements at low tide.


68 posted on 08/16/2004 9:37:30 PM PDT by U S Army EOD (John Kerry, the mother of all flip floppers.)
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To: SunkenCiv
"The melting of the ice caps is, as you said, another fiction. Antarctica's average ice depth is puffed up by the submerged ice (where most of Antarctica's ice is), which, if it melted, would not do anything to sealevel, other than possibly slightly reducing them. Furthermore, the oceans don't rise due to warming at depth (that's the latest non-factual claim to which the global warming demagogues have retreated) -- the oceans don't warm at depth, they get colder and heavier with minerals and whatnot with depth."

I believe you are confusing the Arctic and the Antarctic. The Arctic ice cap covers an ocean (conveniently named the Arctic Ocean) and the Antarctic ice cap covers a continental land mass (called Antarctica).

As far as the effect of melting the ice caps goes, you said "if it melted, would not do anything to sealevel, other than possibly slightly reducing them." Ignoring the effects of warming at depth of the water itself (due to the sheer amount of energy involved being enough to sterilize the planet anyway) and discounting the negligible effect of dissolved salts on the total volume of the solution (the volume of the dissolved salts would be effectively constant as seawater is not at saturation) there would be some increase in the total volume of the solution (the world ocean) and therefore some rise in sea level.

Consider the following: an ice cube floating in a glass of water. What happens to the level of the water when the ice cube melts? Well, we know that the ice cube displaces its own weight of water - that is how it floats. Therefore, the portion of the ice cube that is below the water line occupies a volume equal to the volume of water that weighs the same as the ice cube. Since the ice cube is made of water, if it melted it would exactly fill the portion of its own volume that was below the water line before it melted. So the water level in the glass (sea level) will not change when the ice cube melts.

But that only accounts for floating ice. What about those portions of the ice cap that are on land, or resting on the bottom where the ocean is shallow? In that case, where the ice is displacing less than its own weight of water, it would contribute to a net rise in sea level. This effect is probably negligible for the Arctic as there is little land area there and the Arctic Ocean is deep enough that the permanent ice cap reaches the bottom in few areas. The big concern would be if the Antarctic ice cap melted. Virtually all of it sits on top of Antarctica. This would cause the oceans to rise substantially. Of course, to melt the 26.4 billion cubic meters of ice in the Antarctic ice cap would take 2.4 trillion kilowatt-hours just to melt 0 degree (Celsius) ice to 0 degree water. That doesn't include warming all that ice up to the verge of melting in the first place.
69 posted on 08/16/2004 11:15:50 PM PDT by calenel (Peace Through Strength, and when necessary, Peace Through Victory!)
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To: U S Army EOD; SunkenCiv

ROFL!

That is more scientific than what they are doing.


70 posted on 08/16/2004 11:15:59 PM PDT by Ernest_at_the_Beach (A Proud member of Free Republic ~~The New Face of the Fourth Estate since 1996.)
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To: calenel
The big concern would be if the Antarctic ice cap melted. Virtually all of it sits on top of Antarctica.

Actually, it turns out that a large proportion of Antartica is nothing but very large sea ice sheets. Most of the Ross area, for instance. It's long past time for me to go to bed, I'll research it another time.

71 posted on 08/16/2004 11:28:37 PM PDT by jimtorr
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To: calenel
I'm not confusing anything. The Antarctic ice sheet has most of its volume submerged, off West Antarctica, which means it has already had all the effect on sealevel it is going to have. Naturally, the ice that floats (and seasonally comes and goes) in the Arctic has no effect on sealevel.
What about those portions of the ice cap that are on land, or resting on the bottom where the ocean is shallow?
The portions resting on the bottom are already mostly underwater. Most of the ice in Antarctica is in that category. If it melts -- that is, rises in temperature to the melting point -- the near-freezing liquid would cause a slight cooling and loss of volume in the world's oceans near the surface as it spread out, hence a slight loss of depth. There's no sign that is happening however.
Virtually all of it sits on top of Antarctica.
No, it doesn't, that's the point. Most of the Antarctic ice is already submerged.

If there were a catastrophic heating (and again, there's no sign of that anywhere on Earth), and Antarctica were freed from ice for the first time in circa 2 million years (not 30 million, or 50 million, as is sometimes claimed), isostatic rebound of its continental mass would begin; the long term effect of that would be to deepen the ocean basins, particularly those surrounding the continent. Antarctica has been shedding water for tens of thousands of years, part of its thawing process since the last ice age. Most of the 400 to 800 foot (depending on where on Earth) rise in sealevel after the last ice age came from the vanished glacial sheets.

OTOH, Greenland's ice seems to accumulate depth in a hurry, at least in spots. During the medieval warming ocean levels were higher by feet (this is known because various towns were ports at that time and are not now), and the water went somewhere. As Antarctica has a very low precipitation rate, Greenland, northern Canada, and Siberia appear to be the most probable locations for the subsequent disposal of the water.

72 posted on 08/16/2004 11:47:55 PM PDT by SunkenCiv (Unlike some people, I have a profile. Okay, maybe it's a little large...)
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To: Ernest_at_the_Beach
:')
73 posted on 08/16/2004 11:49:27 PM PDT by SunkenCiv (Unlike some people, I have a profile. Okay, maybe it's a little large...)
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To: SunkenCiv

We had a long thread on that some time back , may still have a bookmark...

Will see if I can find it tomorrow... I'm tired and going to bed now.


74 posted on 08/16/2004 11:56:03 PM PDT by Ernest_at_the_Beach (A Proud member of Free Republic ~~The New Face of the Fourth Estate since 1996.)
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To: MP5
But how do we explain Sean Penn?

Not Global warming...

Must be local inbreeding.
75 posted on 08/16/2004 11:59:15 PM PDT by broadsword (Liberalism is the societal AIDS virus that thwarts national defense.)
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To: Guillermo

A body immersed in water displaces a body of water equal to its own mass... or something like that.


76 posted on 08/17/2004 12:01:31 AM PDT by broadsword (Liberalism is the societal AIDS virus that thwarts national defense.)
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To: ckilmer
It's late and I'm tired..read the title..and immediately thought...geez...ancient romans had fish shaped bics??

Red

77 posted on 08/17/2004 12:02:52 AM PDT by Conservative4Ever (I love the 1st Amendment...I can call Clinton an idiot.)
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To: Nathaniel Fischer

What's that?
the "I can't think" syndrome for scientific discovery?


78 posted on 08/17/2004 12:09:22 AM PDT by Robert_Paulson2 (the madridification of our election is now officially underway.)
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To: farmfriend

BTTT!!!!!!


79 posted on 08/17/2004 3:04:04 AM PDT by E.G.C.
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To: ckilmer

From another article on the same website:

"The controversial idea that cosmic rays could be driving global warming by influencing cloud cover will get a boost at a conference next week. But some scientists dismiss the idea and are worried that it will detract from efforts to curb rising levels of greenhouse gases."


80 posted on 08/17/2004 3:11:12 AM PDT by Fresh Wind (Uday is DU in Pig Latin)
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