Australia shipping alert over massive iceberg

[RedCloud]

Source: Yaho news

SYDNEY (AFP) – Australian authorities Friday issued a shipping alert over a gigantic iceberg that is gradually approaching the country's southwest coast.

The Bureau of Meteorology said the once-in-a-century cliff of ice, which dislodged from Antarctica about a decade ago before drifting north, was being monitored using satellites.

"Mariners are advised that at 1200 GMT on December 9, an iceberg approximately 1,700 kilometres (1,054 miles) south-southwest of the West Australian coast was observed," it said, giving the iceberg's coordinates.

"The iceberg is 140 square kilometres in area -- 19 kilometres long by eight kilometres wide."

Read more: http://news.yahoo.com/s/afp/20091211/wl_afp/australiaantarcticaiceberg

[phantom power]

1. For your entertainment, I will now predict the future...

Icebergs of this size are no longer "once-in-a-century."

[RedCloud]

4. And if we think of our ocean as a glass of water...

what happens to the level when you add ice?

[GreenStormCloud]

5. That iceberg was already afloat when it broke off the ice shelf.

It will have no effect on the sea levels at all. It's mass was already displaced by the same mass of sea water. When it melts volume of the melt water will exactly equal the volume of the displaced water, so it evens out.

[Sanity Claws]

9. But part of the iceberg was above water and thus not displacing water

Once the iceberg melts, top and all, it will raise the water level.
Right?

[ret5hd]

11. No. Wrong.

To verify this place an icecube in a glass. Fill the glass to the brim with water. Watch icecube melt.

Ice displaces the same amount of water that the ice is comprised of.

[Sanity Claws]

12. But one-third of each ice cube does not float above the top of the water

One-third of an iceberg is above water.

[ret5hd]

13. The only diff between "types" of ice is the amount of gasses trapped in the ice...

which, when released from the ice will not contribute to a rise in levels. Ice is ice is frozen H2O. The weight of frozen H2O will displace the same weight of unfrozen H2O.

[Thor_MN]

19. That because water expands as it freezes

Contrary to most materials, Water expands as it freezes, due to ice crystals occupying more space than randomly order water. Because of this, the density of ice is less than that of water, meaning ice floats. The amount of space that the water contained in the ice occupies when melted is exactly the same amount of space taken by the submerged ice.


So that ice floating above the water is exactly the amount of extra space taken when the water was frozen. Also it is much less than 1/3 of an icberg above the water. It's more on the order of 1/8 above the water, but (mostly) freshwater iceberg floating in seawater (containing salts) complicates the exact amount for each iceberg.

[mikelgb]

17. Despite title this is a good you tube of Mr. Wizard demonstrating this.

I question the assumption though that this iceberg calved from the sea, it could have very well broken off a land-supported piece.

[DCBob]

16. Correct, however, as more of the ice shelf breaks off, it could allow some land ice to move...

into the ocean which would of course raise ocean levels.

[GreenStormCloud]

22. No. Once it is floating, it doesn't hold land ice on land.

If the land ice is moving, it just pushes the floating ice further out.

I am skeptical about claims that Antarctica is melting. The land temperatures there, even in summer are well below freezing. A warming of even ten degrees, which is a huge warming, still leaves the Antarctica temperatures way below freezing. If things get hot enough for Antarctica to melt, the rest of us have already roasted long ago.

NOTE: Skepticism about Antarctica melting does NOT mean I am a deniar of global warming. Global Warming is real, but some of the effects have been hyped and others have been misunderstood.

[DCBob]

23. Actually, according to some glaciologists it can..

WILKINS ICE SHELF - A huge Antarctic ice shelf is on the brink of collapse with just a sliver of ice holding it in place, the latest victim of global warming that is altering maps of the frozen continent. "We've come to the Wilkins Ice Shelf to see its final death throes," David Vaughan, a glaciologist at the British Antarctic Survey (BAS), told Reuters after the first -- and probably last -- plane landed near the narrowest part of the ice. The flat-topped shelf has an area of thousands of square kilometers, jutting 20 meters (65 ft) out of the sea off the Antarctic Peninsula.But it is held together only by an ever-thinning 40-km (25-mile) strip of ice that has eroded to an hour-glass shape just 500 meters wide at its narrowest. In 1950, the strip was almost 100 km wide.

"It really could go at any minute," Vaughan said on slushy snow in bright sunshine beside a red Twin Otter plane that landed on skis. He added that the ice bridge could linger weeks or months. The Wilkins once covered 16,000 sq km (6,000 sq miles). It has lost a third of its area but is still about the size of Jamaica or the U.S. state of Connecticut. Once the strip breaks up, the sea is likely to sweep away much of the remaining ice.Icebergs the shape and size of shopping malls already dot the sea around the shelf as it disintegrates. Seals bask in the southern hemisphere summer sunshine on icebergs by expanses of open water. A year ago, BAS said the Wilkins was "hanging by a thread" after an aerial survey. "Miraculously we've come back a summer later and it's still here. If it was hanging by a thread last year, it's hanging by a filament this year," Vaughan said.

Nine other shelves have receded or collapsed around the Antarctic peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002. The trend is widely blamed on climate change caused by heat-trapping gases from burning fossil fuels. "This ice shelf and the nine other shelves that we have seen with a similar trajectory are a consequence of warming," Vaughan said. In total, about 25,000 sq km of ice shelves have been lost, changing maps of Antarctica. Ocean sediments indicate that some shelves had been in place for at least 10,000 years.

Vaughan stuck a GPS monitoring station on a long metal pole into the Wilkins ice on behalf of Dutch scientists. It will track ice movements via satellite. The shelf is named after Australian George Hubert Wilkins, an early Antarctic aviator who is set to join an exclusive club of people who have a part of the globe named after them that later vanishes.

Loss of ice shelves does not raise sea levels significantly because the ice is floating and already mostly submerged by the ocean.

But the big worry is that their loss will allow ice sheets on land to move faster, adding extra water to the seas.Wilkins has almost no pent-up glaciers behind it. But ice shelves further south hold back vast volumes of ice. "When those are removed the glaciers will flow faster," Vaughan said.

http://www.planetark.com/enviro-news/item/51278

[hatrack]

2. Wouldn't you have to kind of . .. really make an effort to not avoid something that big?

Not a sailor myself, so . . .

:shrug:

[ret5hd]

6. "Columbus! LOOK OUT!!!!" Thunk. "We hit fuckin' Cuba!"

[perdita9]

8. Burgs this size are dangerous

It isn't just ships that have to look out for these things. Floating drilling platforms have been pulverized by drifting iceburgs. I can only imagine the repercussions if something this large washes up on a beach somewhere.

[ret5hd]

10. Washed up on a beach? How deep do you think a berg like this goes? And how deep is the water...

on a beach?

[GreenStormCloud]

3. I wanna see the frozen daiquiri that think will make. Scotch over the rock anybody? N/T

[regnaD kciN]

7. "Near...far...whereeeeeeeever you are..."

:evilgrin:

[DCBob]

14. Wow, thats an ice island!

The clueless deniers will say, oh, big iceberg near Australia, that means its getting colder..

[NickB79]

15. Tow that baby to shore for fresh water!

I know, sci-fi dreaming, but that's a LOT of water and Australia is in a decade-long drought.

[alittlelark]

18. +1 My 1st thought.

[Thor_MN]

20. It would take quite a bit to move over 100 cubic miles of ice...

If they could wrap that puppy in a giant condom, they could take the time to tow it slowly, but it would take a lot of energy to move it.

[GreenStormCloud]

21. Is it fresh water ice, or sea ice? N/T