Giant iceberg poised to snap off from Antarctica: scientists

June 1, 2017 by Mariëtte Le Roux
Huge ice blocks breaking off the Antarctic shelf could release vast amounts of water, significantly raising ocean levels

An expanse of ice roughly the size of Delaware is close to breaking off from the warming Antarctic ice shelf to form one of the world's largest-ever icebergs, scientists said Thursday.

On the day President Donald Trump is to announce whether or not the United States will withdraw from the Paris Agreement to limit climate change, satellite data showed that the West Antarctic Larsen C shelf is poised to shed an ice block measuring about 5,000 square kilometres (1,900 square miles).

"The rift in Larsen C is likely to lead to one of the largest icebergs ever recorded," said Swansea University in Wales, whose scientists are monitoring the creeping crack.

The rift, which is threatening to carve off a finger-shaped iceberg about 350 metres thick, expanded by 17 kilometres (11 miles) in six days, leaving just a 13-kilometre thread attaching it to the main ice sheet.

"The timing of calving is probably very close," a university statement said.

"There appears to be very little to prevent the iceberg from breaking away completely."

An ice shelf is a floating extension of a land-covering ice sheet.

Larsen C is the most northerly of the Antarctic ice shelves, as well as the largest. The calving of the iceberg would see it lose about a tenth of its total area, shrinking it to its smallest size on record.

On its own, the huge ice cube would not add to sea level rise.

But its detachment may render the remainder of the Larsen C shelf unstable and vulnerable to collapse, which would release vast amounts of water, scientists say.

Latest shelf to fall

If all the glaciers held back by Larsen C were to run into the ocean, the global water mark would increase by about 10 centimetres (four inches), the researchers said.

The West Antarctic ice sheet holds enough frozen water to raise the average sea level by about six metres (20 feet).

Two smaller shelves on the eastern side of the Antarctic peninsula have already collapsed.

The first, Larsen A, was lost in 1995. Seven years later, the Larsen B shelf followed—at 3,250 square kilometres, it was the size of Rhode Island.

The Larsen B event had no precedent since the end of the last Ice Age some 12,000 years ago, according to glaciologists.

"It is widely accepted that warming ocean and atmospheric temperatures have been a factor in earlier disintegrations of ice shelves elsewhere on the Antarctic Peninsula," the Swansea team said.

Antarctica is one of the fastest warming places on the planet, they added, "a feature which will certainly not have hindered the development of the rift."

Ice shelves break up naturally, but global warming is thought to have accelerated the process, though this has not been scientifically proven.

Scores of countries committed to the 2015 Paris Agreement, which calls for efforts to cap global warming at "well under" two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial era levels.

Temperatures have already increased by 1.1 degrees Celsius from those levels.

On the campaign trail, Trump threatened to "cancel" the global pact, and he has said he will announce his final decision later Thursday.

Explore further: Massive Antarctic ice shelf ready to break apart

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Parsec
4 / 5 (12) Jun 01, 2017
I don't see why everyone is worried about this. As soon as it breaks off, Trump will just tweet that the announcement is fake news and the iceberg will disappear. Its an amazing thing when your fearless leader can change the nature of reality with his fingers and words!
doogsnova
1.4 / 5 (9) Jun 01, 2017
I don't see how this is Trump's fault. He did not cause the overpopulation, which at last count in Dec. 2016 reached 8,739,001,024. No other politician is championing laws to stop or regulate births so that the overpopulation can naturally reach sustainable levels for humanity, flora, fauna, and the planet. And so we will continue to suffer consequences.
Da Schneib
4.3 / 5 (11) Jun 01, 2017
Waiting for the #climatecranks to show up and announce it's a conspiracy theory and nothing happened to the ice shelves in Antarctica, or else explain why all these things are happening because it's actually getting colder.
kochevnik
2.2 / 5 (10) Jun 01, 2017
Since all planets in the solar system are overheating, communist Merkel can simply ban autos on Mars and Venus. That will balance the average temperature, and everyone will be happy. Of course Earth will have a little ice age until 2053 due to solar minimum cosmic ray cloud cover, but the budget was already spent on warming so famines will be rebranded as universal weight loss program
zz5555
4 / 5 (12) Jun 01, 2017
Since all planets in the solar system are overheating, communist Merkel can simply ban autos on Mars and Venus.

Since there's no evidence that all the planets are heating up, where do people get this idea? Mars, in particular, shows no long term warming. There was some some reports of Mars warming based on two photos, however, this has been debunked (https://skeptical...iate.htm ). There's no evidence that Jupiter is warming (https://skeptical...iate.htm ). Neptune is warming because it's moving into summer (https://skeptical...iate.htm ) and that's likely also true for Pluto. In any case, the Neptune (165 years) and Pluto (248 years) orbits are very long, so we can't possibly have enough evidence to suggest long term warming as opposed to seasonal.
Whydening Gyre
3.7 / 5 (3) Jun 02, 2017
What I wonder about....
Doesn't the calving only happen to ice already IN the ocean? Because there is no solid structure under it to assist in maintaining a stable slab (oceanic currents can provide a lot a stress point to that ice sheet) ?
Da Schneib
3.9 / 5 (9) Jun 02, 2017
The point isn't about the calving raising the sea level; most of that already happened whenever the shelf formed. It's about all the ice behind it which is now free to move into the sea, and about how much heat it took to break the shelf off when it's been just sitting there for millennia.

To those two points:

The speed of advance of the glacier behind Larsen B tripled after it disintegrated.

The shelf has been just sitting there since the end of the last glaciation and probably a lot longer than that. Current warming is unprecedented during the current interglacial.
Benni
2 / 5 (4) Jun 02, 2017
Since all planets in the solar system are overheating
.......which has been especially noticeable by actual measurements on Mars, this proves AGW not only threatens planet Earth with apocalyptic consequences, but Mars as well due to the "vacuum energy bridge" that connects Earth & Mars.

If we don't act quickly to prevent calving of Antarctic Ice, Mars will become an even more barren wasteland & will turn to some other color than red & it will be Donald Trumps fault because US citizens are no longer overpaying their fair share of the Paris Climate debacle.

Benni
1 / 5 (4) Jun 02, 2017
The shelf has been just sitting there since the end of the last glaciation and probably a lot longer than that
.........and when the thing finally falls away & melts, ocean levels will drop & you don't even know why do you?

Bart_A
1.6 / 5 (7) Jun 02, 2017
Why is this even news? Just because of the timing to Trump's brilliant move?
There are always icebergs snapping in both the southern and northern hemispheres. It is a natural process.

Larsen C shelf is merely a tenth of the size of larger shelves, and 1/3 of of 1% the size of Antarctica. And a fraction of that broke off. News?

Benni
1 / 5 (4) Jun 02, 2017
Larsen C shelf is merely a tenth of the size of larger shelves, and 1/3 of of 1% the size of Antarctica. And a fraction of that broke off. News?
......on the money.

The real news schould be:

"Larsen C Shelf about to Calve, Ocean Levels to Drop"

kochevnik
1.8 / 5 (5) Jun 02, 2017
Since all planets in the solar system are overheating, communist Merkel can simply ban autos on Mars and Venus.
Since there's no evidence that all the planets are heating up, where do people get this idea? Mars, in particular, shows no long term warming.
Actually Mars is undergoing dramatic global warming now
Benni
2.3 / 5 (3) Jun 02, 2017
Mars, in particular, shows no long term warming.
...........enjoyed the selective use of that term you used: "long term warming". But yes, it is warming on mars, it's a matter of "long term" with respect to Mars, or "long term" with respect to Earth & what the two simultaneous events have in common, but I'm sure you can't figure that out.

kochevnik
1 / 5 (2) Jun 02, 2017
892 icebergs reported seen in 1972. Last year about 200. Icebergs do no correlate with warming, but with thermal perturbations brought by wind reversal and geologic activity
antigoracle
1 / 5 (4) Jun 02, 2017
The shelf has been just sitting there since the end of the last glaciation and probably a lot longer than that. Current warming is unprecedented during the current interglacial.
-- Da Idiot

Uh huh. Glaciers never move and ice never breaks off but AGW Chicken Little idiots surely know how to regurgitate the utter shite they are fed.
nrauhauser
3.4 / 5 (5) Jun 02, 2017
About Mars in particular - it has no atmosphere and no oceans. Repeat after me: "low thermal inertia". Thusly, it warms and cools with minor changes in solar input driven by orbital eccentricity.

Anyone attempting to make generalizations about conditions on Earth based on the "Mars, too" canard is pedaling junk science from various denialist cranks. There *has* been a lot of good snark above related to this, just hadn't seen anyone explain the thermal inertia angle, and some new readers might be confused by this.
SamB
1 / 5 (1) Jun 02, 2017
I Trump will just tweet that the announcement is fake news and the iceberg will disappear.


And the funny thing, if you wait long enough his prediction will come true!
Da Schneib
5 / 5 (2) Jun 02, 2017
I see no serious arguments against the two points I raised above. All I see is #climatecranks. Sorry, man, I got real world stuff to do and if you can't get your sxxt together better than that I'm busy leave a message I'll get back to you later.
bluebug51600
not rated yet Jun 29, 2017
When ice is over water, when it melts, there is no rise to the water level. Try it yourself. Put ice in your cup and then fill it with water to the lip of the cup. When it melts, the level stays the same. This is the kind of scientists that is paid, grants/research money, to put a scare in people so they can keep their jobs. The Earth is cooling, just check the sun spot record. Global warming scientists want it both ways. Methane seeps, ocean floor, may cause global cooling, not global warming. CO2 causes global warming. The findings are a complete reversal of what scientists previously believed — that methane seeps in the Arctic Ocean were contributing to global warming. "It could mean that methane seeps have a net cooling effect on climate, not a warming effect as we previously thought," said John Pohlman, a U.S. Geological Survey biochemist and lead author of the study. Instead of causing massive warming, "these areas of methane seepage may be net greenhouse gas loss,"

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