Thats the antartic jet stream animation builder. Put in your dates and watch how the wind patterns go.. looks like the area you are showing is gettin slammed.

Agreed, the perennial seaice that used to lie off that shore is no longer protecting the ice sheet from the weather, waves and tides etc. hence the mechanical stresses on the ice sheet.

I agree that ice cantilevered off land does not displace its full weight. It is spectacular to watch the glaciers at Glacier Bay fall into the water.
Ice has another property that you can demonstrate with an ice cube. If you place pressure on ice , it melts. There will be some stress relief that will reduce the cantilever area due to melting and refreezing in areas of high stress.
When we talk of the ice that flows from the land into the ocean, that is only part of the story. The major part is due to the water of the ocean freezing. Then snow can build on the frozen ice. The Ocean around Antarctic freezes at the rate of several mile per day during winter. With the thawing and refreezing of the Artic Ocean on the Canadian coastline, I would expect that very little of it is cantilevered.

There is something important that needs to be remembered. When ice is supported by water, it will displace an amount of water equal to it’s weight. (Archimedes Principal) If you place a piece of ice in a glass of water and mark the level of the water, when the ice melts, the level will be the same.

Agreed.

The ice on the Arctic Ocean that is supported by water has already displaced it’s weight and caused water to flow out from the Arctic Ocean. (Emphasis added.)

Disagree. You’re overlooking the mechanical properties of the ice. The sheet ice ice only displacing part of it’s weight. The remainder is cantilevered. See my post regarding what happens when the mass of ice not supported by water exerts enough force to exceed the yield strength of ice. After the ice fractures off of the main body, it is just as you say.

Flanagan,
Wilkins is not in West Antarctica, and from the photos the breakup appears to be mechanical rather than due to melt.”

I agree with Steven. Perhaps the winds are driving what you are seeing?

http://squall.sfsu.edu/scripts/shemjet_archloop.html

Thats the antartic jet stream animation builder. Put in your dates and watch how the wind patterns go.. looks like the area you are showing is gettin slammed.

…and I don’t quite understand what you mean by “mechanical” collapse, as opposed to “melting”. The melting of ice shelves always results in rifts and subsequently in collapses, they do not slowly become liquid, do they?

As the ice sheet advances from land to water, only part of the mass of the ice is supported by water. The rest is “cantilevered” over the water. This creates a bending moment, which induces tensile stress across the top of the sheet. When the tensile stress exceeds the yield stress of the ice, it fails. The physical process is an initial failure in tension, which acts as the fracture initiator. The fracture propagates down across shear planes in the ice sheet, relieving the stress.

If you look at this – http://www.spri.cam.ac.uk/research/projects/larseniceshelf/photos/AP-tabular-iceberg.jpg – you can see the roughness at the top of the sheet typical of tensile failure, while below it’s smooth, the characteristic of shear failure.

This is a mechanical collapse.

I assume that the reference to “melting” refers to a process where melting at top or bottom of the sheet lowering the mechanical strength of the sheet. However, even in that case, the process will still occur as I’ve described – unless someone want to make a silly assertion about ice sheets magically “melting” through across arbitrary planes away from the surface in fashion bearing an uncanny and mysterious resemblance to shear failure.

Hope this answers your question.

Sorry, but it beggars belief that an Ozzie from somewhere near Melbourne would pose as an authority on glaciers, or ice, or snow, or even fresh water!

While I’ve never stood astride a glacier I at least can watch the progress of ice out on a lake every spring. I have a half-dozen adjectives for snow, like scraffle or powder, that I use most winters.

High comedy.

and I don’t quite understand what you mean by “mechanical” collapse, as opposed to “melting”. The melting of ice shelves always results in rifts and subsequently in collapses, they do not slowly become liquid, do they?

(how do I turn sarcasm off on this blog? I hope someone can tell me soon, because I’ve got a hunk of polar bear on the grill and it won’t flip itself!)

And what facts were those? It’s a model not a fact.

Now I’m intrigued. Wikipedia; the people’s “encyclopedia” says some water is 1600 years old !

Not sure how far your tongue is in your cheek on that :)

That is an estimate of the maximum time a parcel of water takes to make its deep water transit in the thermohaline circulation since it descended. I have seen other estimates of various legs of the journey. I think the transit time for the surface loop from the Indian ocean area to the north atlantic is about 50 years. The water now near the UK up welled near India, or passed southwest out of the Pacific during the Korean war period. Likewise the oldest water in the loop which sunk near the UK about the time the Roman Empire fell in about 410 BCE is just now upwelling in the Central Pacific.

The point I was trying to make was the ocean might have a thermal memory in that long loop current, that periodically brings to the surface water that sank decades or centuries earlier. If it does not fully equalize in temperature during its travel, there should be a small bias imposed on the solar heating by the starting point of the heating as this water up wells.

I have no clue if or how big this bias might be, but since the thermal anomalies AGW is so concerned about, (total range from hot to cold anomaly being about 4.5 deg C, with most of the sea surface anomaly much smaller) even a very small bias in absolute terms for the upwelling water temp would/could be a significant fraction of the total anomaly.

Larry