Collapse of Antarctic ice shelf could have global effects

[steve2470]

http://www.cbc.ca/story/science/national/2005/08/03/ice-shelf050803.html

Last Updated Wed, 03 Aug 2005 20:25:54 EDT
CBC News

The unprecedented collapse of an ice-shelf in Antarctic could indirectly lead to a significant rise in global sea levels, researchers say.

The Larsen B ice shelf covered more than 3,000 square kilometres and was 200 metres thick until its northern part disintegrated in the 1990s. Three years ago, the central park also broke up.


An international team of researchers used data collected from six sediment cores near the former ice shelf to show the shelf had been relatively intact for at least 10,000 years or since the last ice age.

The collapse therefore goes beyond what would be expected naturally at the time. Rather, the demise is likely the result of long-term thinning due to melting from underneath, as well as short-term surface melting from global climate change, the researchers suggest.

<snip>

[liberal N proud]

1. COULD?

COULD?
COULD?

What the #$%@
I think it WOULD have global effects. Higher Sea Levels is just one effect with catastrophic results.
These people writing this crap should read it before they print it.

[Tesha]

2. The good news is that Washington, DC is basically at sea level. (NT)

[liberal N proud]

4. OK there will be one plus side to the higher sea levels

Can you say Flush!

[SleeplessinSoCal]

44. What about the Penguins?

I just saw "March of the Penguins" about the Emperor Penguins' courtship and family life. Not to mention the harshest life imaginable.

[KansDem]

9. Knowing the GOP, they'll just switch cars for gondolas...

...and rename the city "Venice DC."

What global warming? What climate change? We want "sound science" or "science that 'sounds' good to us."

DC cabbies might do well to learn singing for their new jobs as gondoliers.

[Tesha]

14. "Constitution Canal" does have a nice, alliterative ring to it. (NT)

[Zhade]

23. Considering how many little de Medicis and Machiavellis are in DC...

...that sounds remarkably appropriate!

[pimpbot]

31. Hey now!!!!! 90%+ of DC residents voted democratic!!

The people you want under water would all flee to the pig farm!

[Dogmudgeon]

3. The sea level is only up slightly

Most of the ice is still ice, although the shelf itself has broken up. I'm sure there would have been a greater sea lewvel rise, but to some extent, warmer air temperatures have resulted in more water vapor going into the atmosphere, and the two forces may have cancelled each others' effects so far.

But scientists say "could" because they don't know for certain. And really, they don't. It's not enough for a scientist to say "the shit's gonna hit the fan", they want to calculate outcomes for all scenarios taking into consideration the quality of the shit and the power of the fan.

I think most of the educated public is aware of this already. And the fan is pointed in our direction.

--p!

[jonkronz2003]

19. here's the real impact

The shelf was holding back the Antarctic glaciers. They will now flow faster into the ocean as they melt, accellerating the process of sea level rise. The shelf itself is not the issue, it's the consequences of that that are important. The Bush admin is studying this and making the necessary revisions to the report as we speak...


"This will be great for cooling off the beaches in this hot summer."

[Dogmudgeon]

25. That makes sense

I hadn't previously considered the process of glacier movement, but it fits in with the rest of what's going on. (I'm afraid I'm a little too fixated on the northern hemisphere.)

Just how much of Antarctica is ice shelf, anyway? 30% or so?

--p!

[Pachamama]

32. The bigger "effect" has to do w/ the temp change of the Ocean from the

melting ice, the effects on currents and thus weather patterns and in turn on the plant and animal life in the oceans and the devastating effects that can have to our food supply etc.

I think that the ripple effect of such a change will be far far more damaging and greater than just DC becoming the Venice of East Coast....

I think Hurricanes and other storm patterns will increase in frequency and intensity...

In a nut shell, I think we are all in for major changes to the world as we know it....and not positive ones either....

[AllyCat]

40. Did you see the PBS special on NOVA about the seaweed that

is taking over the Mediterranean and now parts of the coast of San Diego? One of the theories is that this typically tropical algae has lain dormant in these areas for eons and the rising temps of the oceans are allowing it to flourish. It grows at a rate of an inch a day and covers 40,000 square acres in San Diego now. It chokes out everything and produces high quantities of a single toxin that make it inedible to sealife. The areas where it has taken over look like lawns of green with no fish and no other plantlife.

Think of the impact on the foodchain!

[Pachamama]

46. I did see that NOVA about a year ago - I thought that algae was growing

because it was a non-native invasive plant that somehow got there, but either way, I'm sure that the slight change in temp will have such effects on a dramatic scale on the foodchain and chain of life....

Its insane....we really have no idea how much we are screwing up this planet and the balance of the eco-system. Problem is that by the time people do realize how bad the situation is (because it will be painfully obvious) the rate of change and impact will have such devastating results that will be irreversible and too late to change or stop.

[Xithras]

36. Nonono, you're thinking sheets. This article is about shelves.

The Ross Ice Shelf already floats (floated) on the ocean, so its breakup will have no effect on sea levels. It's seawater to start with. This article is about the Ross Ice Shelf specifically. It's breakup won't affect sea levels, but it may well affect ocean currents around Antarctica and change the way they interact with other currents in the world.

You're thinking of ice sheets, which sit on the land. If those melt we are indeed screwed.

[hatrack]

5. Hell, I've been posting articles on this for over a year

Speed-up on glaciers feeding Larsen B is well-documented, though I'm of course happy to see additional corroboration in this paper.

They've been saying that Larsen C is too far south to undergo the same kind of rapid breakup as its northern sister. As I recall, they said the same thing about Larsen B when Larsen A fell apart in 1995.

[happyslug]

6. Ice Shelves vs Ice Sheets

Ice Shelves are ice floating on water. Larsen B was such a Shelf (as is the Arctic Ocean). Ice Shelfs by themselves are NOT a concern when it comes to raising ocean levels, the reason being as ice floating on water they are already displacing the water the ice will become when melted thus no net increase in world wide ocean levels (There may be a centimeter increase do to expansion of water to the water increase in temperature but nothing drastic).

On the other hand ice Sheets can increase world wide ocean levels. ICe Sheets are grounded i.e. the bottom of the ice sheet is laying on top of the surface of land. If such ice Sheets melts than you additions to how much water is in the ocean and thus ocean levels.

Now you have three big ice sheets today, the Greenland ice Sheet which is grounded above sea level, but is located below the Arctic Circle, the East Antarctic Ice Sheet which is grounded above sea level but within the Antarctic Circle and the real worry, West Antarctic ice Sheet which is located within the Antarctic Circle but grounded BELOW sea level.

Even under some of the most drastic global warming scenario the East Antarctic Ice sheet is viewed as stable (It may even EXPAND under Global Warming). This is do to its location within the Antarctic Circle (Minimal sunlight hitting it) AND that it is grounded above Sea Level (No contact with the ocean and thus not affected by world wide ocean temperature raise). The East Antarctic Ice Sheet contains 70% of the fresh water on this plant and if it would melt raise ocean levels 200 feet, but as I said under most scenarios NOT going to melt.

The two big concerns are the two smaller ice sheets, The Greenland and West Antarctic ICe Sheets. Greenland is Located BELOW the Arctic Circle and thus affected by increase sunlight and global air temperatures, while the West Antarctic ICe Sheet is grounded below sea level and thus affected by raising world wide ocean temperatures. Both Ice sheets take up about 12% of the Fresh water in the world and each could raise ocean levels about 20 feet.

The threat from the Greenland Ice Sheet is that it ill slowly melt and raise Ocean levels over a 50-100 year period (WIth the possibility that parts of it might break off suddenly into the ocean causing the Gulf Stream to dip further south than it does today, this is believe to be the cause of the European mini-ice age from 1500-1800). It is NOT believed that the Greenland ICe Sheet will causes any significant SUDDEN increase in ocean levels (Through may cause a gradual 20 foot increase in ocean levels).

On the other hand it is believe the West Antarctic Ice Sheet, being grounded below Sea level is capable of a sudden collapse, which can lead to a sudden 20 feet increase in world wide ocean levels. This is the big fear.

Now as to the Ice Shelves, the concern as to Larsen B and the other Antarctic Ice Shelves is HOW the Ice Shelves keeps water underneath them so cold that the Ice Sheets are NOT affected by the temperature of the surrounding ocean and thus stay stable. Thus the loss of the Ice Shelves may lead to the loss of the Ice Sheets. Thus the global affect is indirect but may be drastic.

Some more reading on this subject:
http://www.imaja.com/change/environment/can/journal/madhousecentury.html
http://ces.iisc.ernet.in/hpg/envis/doc98html/globalcll1119.html
http://omega.twoday.net/stories/229225
http://omega.twoday.net/stories/229225/


How the Madhouse Century affected Human Evolution:
http://www.press.uchicago.edu/Misc/Chicago/092011.html

[yankeeinlouisiana]

7. Thank you for the explanation.

:-)

[H5N1]

8. Excellent!

[alfredo]

10. What about the drop in salinity due to the melting.

what effect will that have?

[happyslug]

17. The Key to salinity is tied in with the world wide ocean circulation syste

Right now you have a world wide circulation of water. It starts in the Gulf of Mexico driven both by the heat of the sun AND the built up of salt in the shadow waters of the Caribbean (As water evaporates it leaves the salt behind thus Caribbean water tends to get salter and salter over time, the same with the Mediterranean Sea).

The Gulf Steam heads north and dumps its excess heat between England and Iceland (Warming up Europe) but taking its salt down to the bottom of the Ocean. The salt is than carried to the SOuth Atlantic, through the Indians Ocean and then into the Pacific where the salt is dumped into the huge pacific ocean Canyons. Now what goes in must go out (We are talking about a Liquid here) so water than leaves the Pacific back to the Caribbean.

This Ocean circulation system has existed since what is now Central America came into existence ending direct flows from the Caribbean to the Pacific. Now it has shut down during the subsequent Ice Ages, either do to the ice age or causing the ice age (opinions are split but the split may be more of which came first, chicken or the egg debate than a real debate on cause and effect).

Thus if the ice sheets break up AND DISTURB the ocean circulation system you will have increase salt levels in parts of the ocean but do to the lack of Circulation NOT do to dilution by the released Water.

http://www.whoi.edu/institutes/occi/currenttopics/abruptclimate_mcmanus_pr.html
http://www.phys.ocean.dal.ca/~ltang/TLQ_Home/Two_way_nested_Model_in_MBRS_Liqun2.htm
http://www.gsfc.nasa.gov/topstory/20011116meltwater.html
http://www.navo.hpc.mil/Navigator/Spring00_Feature1.html
http://www.grida.no/climate/vital/32.htm
http://eesc.columbia.edu/courses/ees/climate/lectures/o_circ.html
http://web.princeton.edu/sites/pei/pdf/klauskellerpaper.pdf#search='Ocean%20circulation%20system'

[alfredo]

26. Thanks. I have read about the gulf stream slowing.

Has this anything to do with the melting of the poles?

[Dogmudgeon]

33. Yes (polar ice melt)

Not the poles themselves, but the ice at the poles.

The ice melts and freshens (reduces the salinity) of the seawater. This interrupts the thermohaline current, which carries heat up to Northern Europe, the North Pacific, and a couple of spots near Antarctica.

The Atlantic thermohaline current is especially sensitive. Many of the heat transfer currents in the North Sea have been documented to have disappear, and the currents in the North Pacific are known to be "acting strangely".

Changes in the Atlantic thermohaline current are very likely what begins and ends ice ages in the north, and paleoclimatologists are pretty confident that a disruption of this current caused the Younger-Dryas Era, a mini-ice-age that happened shortly after the major ice age had receeded (around 10,000 years ago).

--p!

[alfredo]

34. It seems that the sea life is reacting

to the changes.

What would happen to the US if the gulf stream stopped?

[Dogmudgeon]

35. The Gulf Stream is unlikely to just stop

It would take a long, long time to do that -- a century or more.

But the heat transfer process is already measurably impaired. And in geological terms, a hundred years is pretty quick.

Sea life isn't just reacting to these changes -- a whole lot of it is dying. And dying out. We're in the middle of a Great Extinction. It's been going on for a million years or more, but when we came on the scene, we revved it up like a teenager in a race car.

--p!

[alfredo]

37. I just feel bad that we have not done enough to clean up

our act. Politics and superstition have kept us from responding to this crisis. We may not be able to stop it, but maybe we could buy time needed to adapt to the changes.

[happyslug]

38. The most likely situation is that it shifts south to Spain.

What I have read on the net is that since the what is now Central America became land and blocked water from going from the Caribbean to the Pacific the World Wide Ocean Circulation system has had tow "modes". The first mode is the present one, the Second mode is one where the gulf stream flows East to Spain instead of North to England. It than flows south permitting colder temperatures in Europe AND North America. This in turn is believed permit the reestablishment of the North American Ice Sheet (Which melted away 10,000 years ago).

All told the circulation system goes a a truncated path till it switches again to the north. What causes the Switch no one knows but could it be the West Antarctic ICe Sheet? WAIS could do this by dumping all of its water at once into the acne stopping to movement of water. Another way may be the additional water off WAIS and Greenland slow down the Current since both tend to flow AGAINST the prevailing currents. Prue speculation on my part but read up on the mad house Century and it is not as far fetched as it first appears.

A third explanation may be the release of the WAIS churns up trace minerals into the ocean deserts of the South Indian and South Pacific that caused the plankton to grow in these areas. The Plankton than fixes so much Carbon Dioxide that the world wide temperatures starts to drop drastically and you have a new ice age.

The deep Blue is the ocean Deserts:


http://www.coexploration.org/bbsr/classroombats/html/ocean_properties.html
http://www.sciencedaily.com/releases/2004/04/040420013836.htm
http://www.usc.edu/uscnews/stories/2203.html
http://www.scoop.co.nz/stories/SC0403/S00073.htm
http://www.volvooceanadventure.org/volvooceanadventure/article.php/rz_1_rom_01_rl_00100_00200.shtml
http://www.sciencedaily.com/releases/2004/06/040621074822.htm
http://www.volvooceanadventure.org/volvooceanadventure/image.php/oz_2_occ_03_sc_00300/deserts.shtml

[Xithras]

41. Very little effect on the US

The Eastern US coast from Cape Hatteras south might see a minor drop in their average temperatures, but their southern location will mitigate any serious impacts. The greater danger is to our fisheries...the north Atlantic fisheries would crash overnight if the Gulf Stream were to alter in any significant way.

Europeans are really the ones who are in danger from a weakening of the Gulf Stream. The massive temperature drops would make much of Northern Europe, Great Britain, the Scandinavian nations, and northern France and Germany, resemble northern Canada or Alaska. Farms would fail, winter would lengthen by months, and snowfall would increase astronomically. The North Sea and Baltic would see massive increases in sea ice, impacting shipping and devastating the economies of the nations that depend on those bodies.

Then you have to deal with migration issues. When all of the residents of Glasgow realize that their average summer temps will be in the mid-40's rather than the mid-70's they're used to, many are going to try and move. Multiply that by all of the cities in all of the EU nations, and you'll end up with a HUGE human migration. All of those people are going to pack into southern Europe, causing countless problems as economies and social programs crash under the influx of new people.

[alfredo]

43. Are our environmental policies or rather lack of affirmative

actions on the environment shaped by the realization that Europe would fare much worse than us.


What about Asia?

[klyon]

11. thanks

KL

[Kraklen]

15. Alright, answer me this...

with the collapse and dispersal of the ice shelves, the ice sheets are free to advance into the ocean and subsequently raise the level.

With the collapes of the Larsen shelves, which sheets will be advancing?

[happyslug]

16. The whole West Antarctic Ice Sheet (WAIS)

That is what is believed to have happened 120,000 years ago, the whole ice sheet just literally fell into the ocean. This is why you will hear people call the WAIS the Godzilla of Global Warming.

[Eloriel]

18. How sudden is "sudden"?

On the other hand it is believe the West Antarctic Ice Sheet, being grounded below Sea level is capable of a sudden collapse, which can lead to a sudden 20 feet increase in world wide ocean levels. This is the big fear.

With as much warning as a tsuanmi (and yes, I realize distance provides opportunity for more warning time)? Or more than that?

[Kraklen]

21. I think they mean sudden on different scale.

Years, not seconds.

[Dogmudgeon]

27. How long? There's a lot of ice involved.

It should be calculable, but I have never seen it. "X amount of ice being warmed in water at Y kelvins." My wild-assed guess is that a free ice sheet, being a mile or more thick, might take a hundred years to fully melt; but even a few years of that melting could raise the water level enough to cause some serious flooding. Florida, Holland, and Bangladesh, for example.

Tsunami effects are harder to figure, but if even a smallish part of the sheet "hits" the water instead of slides in slow, there will be some enormous global tsunamis to deal with.

--p!

[happyslug]

39. I fear it may be MONTHS instead of years

That is what is suggested by the records of the "Mad House Century". Months for the West Antarctic Ice Sheet to collapse and than years for it to be restored and start the next ice age.

[happyslug]

47. One more comment on "Sudden"

The West Antarctic Ice Sheet (WAIS) is grounded on sea bed broken up by islands. It is also volcanic. The worse case scenario as to the WAIS is that sometime in the southern fall (i.e. March or April) after a full summer of sunlight that the Ice Sheet looses their moors to the ground and surrounding ice sheets in the Antarctic Mountains. If this happen the the Ice Sheets of the WAIS will break up and float into the Ross Sea and Wendall sea. This may even occur within the period of one day.

Now the ice will take years to melt, but the effect on world wide ocean levels will be felt within days. The reason for this is once the ICe Sheets start to float, they will be displacing the water their are made of. Presently as ice Sheets they are NOT displacing their volume in water. In simple terms once the Ice Sheets break up and float into what is called the Southern OCean (The OCean right around Antarctica) the affect on world wide ocean levels will be the same as if the Ice Sheets had melted.

[karlrschneider]

20. Something you wrote has me confused

"Now you have three big ice sheets today, the Greenland ice Sheet which is grounded above sea level, but is located below the Arctic Circle,..."
--------------------------------------

I don't have a map handy but I'm pretty sure Greenland is north of the Arctic circle...???
K

[Kraklen]

22. Most of Greenland is north of the arctic cirle.

A chunk extends south. Nevertheless, the sheet's receding.

[happyslug]

30. This map shows the Arctic Circle, goes right through Greenland

http://nsidc.org/arcticmet/basics/arctic_definition.html

The basic Rule as to the Arctic Circle is a point where the sun does not set on the Summer Solstice (Generally June 21st) and does not raise on the winter solstice (Generally December 21st). This is 66 degrees, 32 minutes North Latitude.

On the other hand if you want that period to last months you have to go further north.

Please note on the above map the we are referring to the light blue dashed line. The black line represent the tree line (i.e. the point north where trees no longer grow) and the Red line is the 10 Degree Celsius (50 Degree Fahrenheit) point, where Average Summer Temperature does not exceed 10 Degree Celsius or 50 degree Fahrenheit. Both are used to define the "Arctic Region" as opposed to the Arctic Circle.

I did err in one regard, I had been using 60 Degree for the Arctic Circle where the Circle is much further south (66 degrees, 32 minutes North). 60 Degree north barely touches Northern Greenland while the true Arctic Circle covers over half of the island.

[Dogmudgeon]

42. Outstanding job, happyslug!

I just hope something useful comes of our collected efforts.

--p!

[karlrschneider]

48. Well, your map shows that the 60 deg north lat passes over the very

southern tip of Greenland so it is all north of 60...and about 75 or 80 percent is north of the arctic circle. Are you sure you know the north pole is at the center of that map?...'cause I still can't figure out what you're trying to say...

[mtnester]

12. This is the devil trying to confuse us

global warming is a trick the devil is trying to play on us. There is no science, science is also a trick of the devil...nothing to see, move along



:sarcasm:

[Deja Q]

13. The Titantic told the iceberg it was unsinkable...

The iceberg proved it wrong.

[Carolab]

24. What will happen first? This or the Tsunami?

Apparently there is a fairly good risk of one hitting the east coast due to erosion at the shoreline and also if there is a break in a volcano across the Atlantic that causes a huge slide into the ocean...

{snip}

In August this year, one of Day's colleagues, Bill McGuire, told a conference on global geophysical disasters that Cumbre Vieja could blow "any time" and warned that there was insufficient watch on the volcano.

Only two or three seismographs were deployed there and this number falls way short of giving the weeks-long warning needed to evacuate coastal cities, McGuire said.

"Eventually, the whole rock will collapse into the water, and the collapse will devastate the Atlantic margin," McGuire said. "We need to be out there now looking at when an eruption is likely to happen... otherwise there will be no time to evacuate major cities."


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http://www.terradaily.com/2004/041226152117.76iv431d.html

[Dogmudgeon]

29. Cumbre Vieja has been way over-hyped

I dispute that the tsunami will be as high as the Day study indicates. Even Day and company hedged their bets.

First, Cumbre Vieja is not in as bad a state as it is said to be. The island is not on the verge of collapse. Yes, it's approaching a state where a massive landslide will be inevitable, but it's not immanent. The day of reckoning is not likely to happen any time soon. And a series of smaller, controlled landslides have been discussed.

Second, I think they've overestimated the intensity of the landslide. The model for the run was the Lituya Bay landslide in 1958, which was a very sharp drop, sharper than Cumbre Vieja. And the basin of Lituya Bay amplified the tsunami, while the wide-open Atlantic would tend to damp it.

No doubt about it, there is a real risk, but I think it's been hyped.

Now, when you talk about geological threats, I am more concerned about the Yellowstone supervolcano. It has been increasing in activity since around 1990, and the overall trend has been toward more and more activity. An eruption of Yellowstone would produce over 2000 times as much impact as Mount Pinatubo did. Pinatubo depressed global temperatures by about a degree; a supervolcano eruption would subject us to a several-year-long volcanic winter. Much of the northern hemisphere would be covered by dirty ice and snow for five, ten years or more. Agriculture world wide would simply stop for a decade. The effects of a climate flip-flop or a post-Peak-Oil economic crisis would be small peanuts compared to a supervolcano eruption.

The good news is that it may take another thousand years for this to happen. The bad news is that, then again, it may take another six months for this to happen.

--p!

[Up2Late]

28. I'm much more concerned by the Jakobshavn Isbrae glacier...

...in western Greenland. NOVA Science just did a short (7 minute) report on it, which can be viewed on-line. The website has a bunch of great info, including more on other retreating glaciers. Check it out:

<http://www.pbs.org/wgbh/nova/sciencenow/3210/03.html>

<http://www.pbs.org/wgbh/nova/sciencenow/>

Unfortunately the transcript isn't available yet, but what it will say is the average glacier moves about 1 foot per day, this one, the Jakobshavn Isbrae, Greenland's Largest glacier is now moving, on average 113 feet PER DAY! It has shrunk, over the last 5 years by 8 miles! And it is thought to be responsible for over 4% of Sea Level rise Globally.

Like I said, the video is available at the links above.

[sintax]

45. This is all connected to techno-consumers

and the onslaught of industrial-techno culture which refuses to acknowledge limitations.

Noone wants to give up their toys and everyone has a thousand rationalizations as to why they "need" their cell phone.

Of course the World's Greatest Polluter-The US Military ain't helpin' matters.