Team says Arctic ice shelf broke up before

Oct 25, 2011 by Bob Yirka report
ice shelf
Image: NASA/Goddard Space Flight Center

(PhysOrg.com) -- Arctic shelf ice has been in the news of late due to its shrinkage over the past few decades that most attribute to global warning. Thus, its levels and seemingly constant calving have become ecological barometers that environmentalists have come to use to show just how fast our planet is heating up.

Now however, new research by a team from Université Laval in Canada, led by Dermot Antoniadesa, have found, after studying sedimentary material on the bottom of the Disraeli Fiord, created by backup from an in Northern Canada, that it experienced a major fracture that resulted in an overall reduction of the ice shelf some 1,400 years ago. Which means this isn’t the first time that the shelf ice has melted and broken apart. The team has published the results of its survey in the Proceedings of the National Academy of Sciences.

Shelf ice is a thick platform of ice that has been pushed out to sea by glacier pressure. As the sea level drops, the ice tends to float even as it’s still connected to the shore. Hence its name, it literally looks like a giant shelf hanging off the land out into the sea. One ice shelf in particular, Ward Hunt, located on Ellesmere Island, lies off the north central coast of Canada and is part of a group of ice shelves that once comprised most of the northwest coast of the Island. Over the past hundred years, the shelf ice in this region has diminished by nearly 90%.

Because ice shelves also act as dams, backing up water into fjords, sediments from them build up on the sea floor and in the spaces between the salty seawater and fresh water produced by melting ice. By analyzing these sediments using carbon 14 dating and other techniques, the researchers are able to create a record or timeline of sorts that they can use to look into the past. In this case, the research team found that the ice shelf first appeared approximately 4,000 years ago and hung around for several thousand years. But then about 1,400 years ago, a major fracturing occurred that caused the shelf to shrink. It didn’t fully recover until about 800 years ago. After that, it held steady till the shrinkage that began nearly a hundred years ago and continues to this day.

At this point, it doesn’t appear that the around Ellesmere Island is any smaller now than it was during the previous period of warming, but because it’s still shrinking, it’s possible it could become, as Antoniadesa writes, an “unprecedented” event.

Explore further: NASA's HS3 mission continues with flights over Hurricane Gonzalo

More information: Holocene dynamics of the Arctic's largest ice shelf, PNAS, Published online before print October 24, 2011, doi:10.1073/pnas.1106378108

Abstract
Ice shelves in the Arctic lost more than 90% of their total surface area during the 20th century and are continuing to disintegrate rapidly. The significance of these changes, however, is obscured by the poorly constrained ontogeny of Arctic ice shelves. Here we use the sedimentary record behind the largest remaining ice shelf in the Arctic, the Ward Hunt Ice Shelf (Ellesmere Island, Canada), to establish a long-term context in which to evaluate recent ice-shelf deterioration. Multiproxy analysis of sediment cores revealed pronounced biological and geochemical changes in Disraeli Fiord in response to the formation of the Ward Hunt Ice Shelf and its fluctuations through time. Our results show that the ice shelf was absent during the early Holocene and formed 4,000 years ago in response to climate cooling. Paleoecological data then indicate that the Ward Hunt Ice Shelf remained stable for almost three millennia before a major fracturing event that occurred ∼1,400 years ago. After reformation ∼800 years ago, freshwater was a constant feature of Disraeli Fiord until the catastrophic drainage of its epishelf lake in the early 21st century.

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User comments : 19

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rubberman
2.5 / 5 (16) Oct 25, 2011
IF anyone attempts to use the fact that this happened in the past, prior to the human contribution of the industrial age to GHG's, to justify that the current situation is part of a natural cycle, your time would be better spent going and camping on the current edge of the shelf.....actually go there in May and camp then.
NotParker
2.6 / 5 (18) Oct 25, 2011
rubberman, you may wish the earth to go back to the "good old days" of the Little Ice Age when glaciers were growing and crushing small towns and crops failed all the time. But I don't.

Thankfully the same mechanism that cooled the earth before LIA has allowed it to warm up a little starting around 1750 ...
AAhhzz01
2.8 / 5 (13) Oct 25, 2011
IF anyone attempts to use the fact that THIS happened...or THAT happened...or THE OTHER happened....

Well...if facts are off the table then we are forced to base our opinions on belief like you are rubberman.

Good luck, let us know when you have zero carbon emissions.
rubberman
1 / 5 (5) Oct 25, 2011
I can give you guys a ride up there......
Martian
2.3 / 5 (3) Oct 25, 2011
It happend before, it can happen again...or maybe it won't, we're all just guessing.

Ancient history is a crap-shoot.
CSYGUY
3.7 / 5 (13) Oct 25, 2011
It appears someone has a bad case of cognitive dissidence. Since they can not or will not change their belief / opinion they must attack anything that does not agree with their belief.

I am not sure what is going on with man's contribution to the current warming trend, but what I find morally objectionable is supposed authorities teaching our younger generation that it is not the facts that determine the validity of the scientific theory but the nobility of the cause that should and does rule the day. Shame on you!
PinkElephant
3.2 / 5 (13) Oct 25, 2011
you may wish the earth to go back to the "good old days" of the Little Ice Age
The EARTH was never in any Little Ice Age. Parts of the northern high altitudes, most notably Europe, appear to have been relatively cooler for a few centuries. The rest of the Earth was not. Therefore, the LIA and the MWP have no relevance to modern GLOBAL climate trends. Their underlying causes also have no relevance to the modern ANTHROPOGENIC change in atmospheric chemistry and optics.
supposed authorities teaching our younger generation that it is not the facts that determine the validity of the scientific theory
Whatever authorities have taught you to shamelessly lie in public, have apparently done a pretty decent job.
omatumr
1.2 / 5 (17) Oct 25, 2011
Now however, new research by a team from Université Laval in Canada, led by Dermot Antoniadesa, have found, after studying sedimentary material on the bottom of the Disraeli Fiord, created by backup from an ice shelf in Northern Canada, that it experienced a major fracture that resulted in an overall reduction of the ice shelf some 1,400 years ago. Which means this isnt the first time that the shelf ice has melted and broken apart. The team has published the results of its survey in the Proceedings of the National Academy of Sciences.


Thank you for the report, and thank you PNAS for publishing both sides of this issue!

The global climate scandal seems to be mostly a government propaganda campaign:

Deep roots of the global climate scandal (1971-2011)

http://dl.dropbox...oots.pdf

With kind regards,
Oliver K. Manuel
http://myprofile....anuelo09
PinkElephant
3.8 / 5 (5) Oct 25, 2011
Parts of the northern high altitudes...
I meant to say *latitudes*...
PinkElephant
4.6 / 5 (13) Oct 25, 2011
@ohmytumor,

Seeing as you live in a cave (apparently) and haven't yet heard of BEST -- I recommend you take a look (unless you consider them part of more "government propaganda"):

http://berkeleyea...riations

Pay attention to page 4. Those "up and down" swings over the decades that you find so objectionable, are apparently caused by the AMO. An AMO cycle superimposed on an otherwise rising trend.

Here's hoping your still have enough neurons left in that festering skull to actually comprehend this much. Then again, I'm probably being too optimistic, as usual...

Now, considering BEST quite accurately reproduced the global temperature data from GISS and CRU --

http://berkeleyea...ysis.php

http://berkeleyea...y_20_Oct

-- I expect you to retract and APOLOGIZE FOR your ongoing slanderous invocations of "global climate scandal".

Or don't, and remain the epic failure of a troll that you are.
ryggesogn2
1.7 / 5 (15) Oct 25, 2011
he EARTH was never in any Little Ice Age.

So you assert.
PinkElephant
4.5 / 5 (10) Oct 26, 2011
he EARTH was never in any Little Ice Age.

So you assert.
So asserts every scientific study I've seen in the last several years.

On quite a few of which you and trolls like you left your usual trail of impenetrably inane 'critique', in what one can only interpret as a strenuous and ongoing discipline of preventing yourselves from actually soaking in any of that information.
Shadeburst
3.5 / 5 (2) Oct 26, 2011
I loved the article because it is presented as the findings of pure research without any attempt to align with a political agenda.

Because I love knowledge, I like to test my assumptions whenever contrarian evidence comes up. I am always ready to throw out these assumptions when I learn that I was wrong. Thank you @omatumr as well as @PinkElephant for giving me some meat to chew on.
rubberman
1 / 5 (2) Oct 26, 2011
aahhzz, I never said facts were off the table, my point of view regarding GHG's and the human contribution to them is solely based on facts and observational evidence. I merely suggested not to USE THIS FACT in an attempt to suggest that the current warming trend is part of a natural cycle. I don't beleive anything unless it is proven to my satisfaction. The overwhelming abundance of physical and observational evidence linking human activities to climate change is the reason for my initial post. Put very simply, denying human involvement in the current (and rapidly progressing) climate change is ignorance. Anybody who truly wants to learn the facts can. And if you look at a global climate picture based on all of the observed evidence available to you and still truly beleive that the changes we are witnessing today are part of ANY normal cycle that has occured before, then you would have to be mentally challenged.
rubberman
1 / 5 (2) Oct 26, 2011
As far as my zero carbon footprint...it will be when I die. However, given that I live in the country that has the WORST carbon footprint per capita on earth, My own is VERY low.
jsdarkdestruction
1 / 5 (2) Oct 27, 2011
Oliver Manuel's recent efforts to plaster Physorg.com and other public news sites with his theories and personal URLs are a bit puzzling, as scientists have a variety of publications available to communicate directly to each other in. My best guess is that he is desperately trying to prop up his legacy in light of his arrest in his university office on 7 charges of rape and sodomy based on allegations by 4 of his own children. The charges have been reduced to one count of felony attempted sodomy, not necessarily because of his innocence, but because of the statute of limitations. One can only guess how the recent charges and decades of family strife have affected his ability to reason rationally and to remain objective while defending his unpopular theories.

http://mominer.ms...hildren/

http://www.homefa...uel.html

hush1
1 / 5 (1) Oct 28, 2011
Oliver Manuel enjoys a following. Some follow him with charges. Others with ratings. And a few with on topic comments. Fewer still with off topic comments. Personal guessing strengthens the person's position you oppose. The way I personally follow this person is with a lack of response to any of his input. There many ways to follow a person.
JohnMoser
1.8 / 5 (5) Oct 29, 2011

"IF anyone attempts to use the fact that this happened in the past"

Let's not use facts. That would too close to science.
JohnMoser
1 / 5 (4) Oct 29, 2011
PinkElephant instead of attacking everyone who disagrees with you, perhaps you can explain how the story that is being discussed(did you read it?)fits into your world view.