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End of the World ?

 
 
gollum
 
Reply Fri 10 Feb, 2017 04:59 am
New York Times

A Crack in an Antarctic Ice Shelf
Grew 17 Miles in the Last Two Months
By JUGAL K. PATEL FEB. 7, 2017

A rapidly advancing crack in Antarctica’s fourth-largest ice shelf has scientists concerned that it is getting close to a full break. The rift has accelerated this year in an area already vulnerable to warming temperatures. Since December, the crack has grown by the length of about five football fields each day.

The crack in Larsen C now reaches over 100 miles in length, and some parts of it are as wide as two miles. The tip of the rift is currently only about 20 miles from reaching the other end of the ice shelf.

Once the crack reaches all the way across the ice shelf, the break will create one of the largest icebergs ever recorded, according to Project Midas, a research team that has been monitoring the rift since 2014. Because of the amount of stress the crack is placing on the remaining 20 miles of the shelf, the team expects the break soon.

“The iceberg is likely to break free within the next few months,” said Adrian J. Luckman of Swansea University in Wales, who is a lead researcher for Project Midas. “The rift tip has moved from one region of likely softer ice to another, which explains its step-wise progress.”

The time-lapse image below shows the rift gradually widening from late 2014 to January of this year.

Ice shelves, which form through runoff from glaciers, float in water and provide structural support to the glaciers that rest on land. When an ice shelf collapses, the glaciers behind it can accelerate toward the ocean. Higher temperatures in the region are also helping to further the ice shelf’s retreat.

If the ice shelf breaks at the crack, Larsen C will be at its smallest size ever recorded.

That would also leave the ice front much closer to the ice shelf’s compressive arch, a line that scientists say is critical for structural support. If the front retreats past that line, scientists say, the northernmost part of the shelf could collapse within months. It could also significantly change the landscape of the Antarctic peninsula.

“At that point in time, the glaciers will react,” said Eric J. Rignot, a glaciologist, professor at University of California Irvine and a senior scientist at the NASA Jet Propulsion Laboratory. “If the ice shelf breaks apart, it will remove a buttressing force on the glaciers that flow into it. The glaciers will feel less resistance to flow, effectively removing a cork in front of them.”
The crack in Larsen C is a third of a mile deep, down to the floor of the ice shelf.

According to Dr. Rignot, the stability of the whole ice shelf is threatened.
“You have these two anchors on the side of Larsen C that play a critical role in holding the ice shelf where it is,” he said. “If the shelf is getting thinner, it will be more breakable and it will lose contact with the ice rises.”
Ice rises are islands that are overriden by the ice shelf, allowing them to shoulder more support of the shelf. Scientists have yet to determine the extent of thinning around the Bawden and Gipps ice rises, though Dr. Rignot noted that the Bawden ice rise was a much more vulnerable anchor.
“We’re not even sure how it’s hanging on there,” he said. “But if you take away Bawden, the whole shelf will feel it.”

The Larsen A and B ice shelves disintegrated in 1995 and 2002, though both were drastically smaller than Larsen C. Neither contributed significantly to global sea level rise, however, because they were already floating above water, and the glaciers behind them did not contain a substantial volume of ice.

According to Dr. Rignot, the collapse of Larsen C would add only a tiny amount of water to the global sea level. Of greater concern to scientists is how the collapse of ice shelves can affect the glaciers that flow behind them, because the melting of those glaciers can cause much higher levels of ocean rise. Scientists see the impending Larsen C collapse as a warning that much larger amounts of ice in West Antarctica could be vulnerable.
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Type: Question • Score: 0 • Views: 1,157 • Replies: 11
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Skeleton
 
  0  
Reply Fri 10 Feb, 2017 08:19 am
What are you snorting?
dalehileman
 
  1  
Reply Fri 10 Feb, 2017 03:04 pm
@Skeleton ,
Come on Skel, it's interesting even if it leaves us wondering about effects on the future
0 Replies
 
rosborne979
 
  1  
Reply Fri 10 Feb, 2017 03:21 pm
@gollum,
Inevitable
gollum
 
  2  
Reply Fri 10 Feb, 2017 04:29 pm
@rosborne979,
rosborne979-

Thank you.

As I set it, the question is the rate of change of the ice on Antarctica.

I think the mainstream belief among scientists has been (is?) that the melting of ice and the resulting rise in the sea level will be gradual.

I think that there has been a minority view that the ice might slide off Antarctica causing a sudden rise in the ocean level of a great many feet.

The reason for my Posting was my fear that a sudden rise in ocean level is not far more likely.

rosborne979
 
  1  
Reply Fri 10 Feb, 2017 09:54 pm
@gollum,
The word "Sudden" when used in a geological context is very different from our daily expectation. When reading any information related to geological activity it's important to get an accurate understanding of the timeframe actually being referenced.

In the context of geology all of our cities, and even our entire modern civilization came into being in a flash; a tiny fraction of a "sudden".
gollum
 
  1  
Reply Sat 11 Feb, 2017 05:57 am
@rosborne979,
rosborne979-

Thank you.

I believe the activity in question is the melting of ice on Antarctica.

Based on the melting (and fracturing) it may be that some of the ice on top of Antarctica will slide off and fall into the ocean, causing ocean heights to rise by man feet.

You write of geological activity occurring over very long time periods.

My understanding is that human activity over relatively short time periods caused global warming. I don't see the relevance to geologic activity.
rosborne979
 
  1  
Reply Sat 11 Feb, 2017 08:06 am
@gollum,
In the sources you are taking your information from, do they make any estimates in years or are their predictions all vaguely stated? How many actual years are they talking about?

Human activity didn't cause global warming, but human activity is contributing to global warming. The climate has been warming for much longer than humans have been around, and it does this in a cyclic pattern.
gollum
 
  1  
Reply Sat 11 Feb, 2017 08:21 am
@rosborne979,
rosborne979-

Thank you.

My source is the New York Times article that I posted.

Whether all global warming is caused by human activity or none of it is caused by human activity, the effect on the ice in Antarctica is the same.
Krumple
 
  0  
Reply Sat 11 Feb, 2017 11:00 am
@gollum,
gollum wrote:

rosborne979-

Thank you.

My source is the New York Times article that I posted.

Whether all global warming is caused by human activity or none of it is caused by human activity, the effect on the ice in Antarctica is the same.


I'm half n half. I think solar activity is picking up. There is a lot of data to support it. Not to say humans don't impact the environment because we do. I just don't think it's as severe as the paid scientist want us to believe.
0 Replies
 
Skeleton
 
  1  
Reply Sat 11 Feb, 2017 03:56 pm
I think if this was serious enough to cause so much worry then someone would fix it
0 Replies
 
rosborne979
 
  1  
Reply Sun 12 Feb, 2017 10:36 am
@gollum,
gollum wrote:
Whether all global warming is caused by human activity or none of it is caused by human activity, the effect on the ice in Antarctica is the same.

Yup, that's why I said "inevitable" earlier.

I don't know how much polar ice is lost at the peaks of the cycle, but since the cores represent over a 500k year record, at least some areas of ice must remain even during the brief warm spikes (like the one we are in now), or we wouldn't have the cores as a record.
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