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AbruptSLR

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Re: PIG has calved
« Reply #1 on: July 09, 2013, 11:58:23 PM »
Yuha,

That is a very timely post and proves that ice shelves can calve even during the dead of an Austral Winter.  We will just have to see how fast things accelerate in the Antarctic.

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ASLR
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Anne

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Re: PIG has calved
« Reply #2 on: July 10, 2013, 01:31:35 AM »
Yuha,

That is a very timely post and proves that ice shelves can calve even during the dead of an Austral Winter.  We will just have to see how fast things accelerate in the Antarctic.

Best,
ASLR

ASLR, can you please elaborate on this:
What should not be a surprise, [Prof Humbert] says, is that it has occurred in deep winter when the ocean is covered in sea-ice. This relatively thin covering would always be overwhelmed by the internal stresses in the massive ice shelf.

That comment doesn't explain to me why the calving has happened now, because I don't know the basic assumptions she's making. What impels the glacier and on what sort of bed is it moving?
Wikipedia is interesting for people like me at PIG 101, but seems to cast no light on why winter calving is not a surprise. Can you help out ?

And what are the questions behind this?
What will be interesting now, she [Prof Humbert] adds, is to see how long it takes for the berg to move out of the bay in front of it. It could take several months. TerraSAR-X will provide the tell-tale data.


With many thanks for your assiduous illumination on all matters Antarctic.
« Last Edit: July 10, 2013, 01:51:40 AM by Anne »

AbruptSLR

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Re: PIG has calved
« Reply #3 on: July 10, 2013, 05:19:03 AM »
Anne,

Thank you for you astute questions, and while I may be assiduous, I am more of a student rather than an illuminator, of all matters Antarctic, but I will give the best responses that I can:

- First, I stated that Yuha's post was timely, because I believe that the warm CDW entering the PIG trough is actually protected by the presence of the sea ice; and the timing of the calving both confirms this (in my mind).  Most researchers expect the rate of retreat of the PIG grounding line, GL, to slow as the GL approaches rougher bed conditions; however, if the buttressing action of the Pine Island Ice Shelf, PIIS, (part of which just calved) degrades fast enough, and if the advection of sufficiently warm CDW is strong enough then the GL will continue past the rough terrain that it is approaching.
- Second, I believe that the calving could have happened any time, but that it happened now because the advection of warm CDW cause: (a) sufficient basal ice melt of the local PIIS connecting to shore to weaken it so that; (b) hydrodynamic drag forces from the exiting current and tides, and internal ice stresses (thermal, flexural and shear) to exceed the crack propagation strength (and shear strength) of the local portion of the PIIS connection to the shore.  You should realize that the PIIS is floating (except where it connects to the shore on one or typically both sides of the PIG trough).  The grounded glacier is several kilometers upstream and thus while it continues to slide forward over bedrock and glacial till, its actions has little to do with the calving.  Also, note that the velocity of the ice shelf is faster than the glacier's ice velocity, thus contributing to the thinning of the ice shelf from the GL out toward the face of the ice shelf.  Let me know if you want more details on why the thin outer portion of the ice shelf calves when its internal strength (which weakens as it thins and warms from the CDW) is exceeded by the internal stresses on the ice shelf (significantly associated with the shear restraints from the shores while the center portion of the ice shelf is moving outward faster then the edges).
- Regarding the movement of the berg out of the bay, this is dependent on many factors, including: (a) the strength and directions of the currents (including advection from the salinity gradient of salty water flowing into the lower portion of the trough and fresher water flowing outward at the upper portion of the trough), eddies and tides; (b) storm-action, storm surge, winds and barometric pressure changes; (c) the presence and strength of adjoining sea ice; and (d) the nature of the grounding risks for the berg.  If the berg does not clear the bay, then it may be possible for the PIIS to advance sufficiently to run into the grounded berg; which might temporarily slow the velocity of the ice shelf until the berg became un-grounded; but it is most likely that the berg will float out of the bay during the Austral Spring sea ice break-up.

You should also note that the Thwaites Ice Tongue surged in Sept. of 2012 (when there was still a lot of adjoining sea ice); and you may want to review some of my earlier posts in the "Surge" thread.

I hope that some of this is helpful.  In any event it is a fascinating phenomenon to observe.

Best,
ASLR
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Anne

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Re: PIG has calved
« Reply #4 on: July 10, 2013, 10:49:21 AM »
ASLR,

Thank you for your patience. Much to think about here.

AbruptSLR

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Re: PIG has calved
« Reply #5 on: July 10, 2013, 03:14:14 PM »
Anne,

You can think of the glacial ice as thick honey that flows and thins under the influence of gravity, and when it is thin enough then it floats on top of the ocean water.

Another aspect of this calving event that I did not previously mention is that the crevesse occurred significantly further upstream than experts had previously estimated (resulting in a larger berg); which to me implies that the influence (both basal drag and melting) of the advection of warm CDW is more important than what those experts had previously thought; which further implies that the PIIS may break-up faster than such experts have previously estimated.

Best,
ASLR
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Lynn Shwadchuck

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Re: PIG has calved
« Reply #6 on: July 10, 2013, 03:29:46 PM »
Thanks, Yuha, for posting this. The BBC story is careful to say these calving events occur naturally without climate change but the warm water underneath is speeding things up. The 6-step photos they've posted are great for those of us who don't diligently stay on top of images.
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Peter Ellis

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Re: PIG has calved
« Reply #7 on: July 12, 2013, 06:22:51 PM »
url=http://en.wikipedia.org/wiki/Pine_Island_Glacier]Wikipedia[/url] is interesting for people like me at PIG 101, but seems to cast no light on why winter calving is not a surprise. Can you help out ?


You're overthinking it.  A common misconception is that glaciers only calve in the summer when they warm up, and that in the winter they're held in place by the frozen sea ice all around them.  The professor's just explaining that this is rubbish, and that the PIG could have calved at any time, including winter.  Sea ice is a thin skim on the surface and cannot hold back the calving event, just like you can't use Pringles as bookends.

Anne

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Re: PIG has calved
« Reply #8 on: July 15, 2013, 02:37:55 AM »
Thanks. Makes sense. I get that glaciers move all the time but don't begin to understand what makes them move. Is it really all down to gravity?

AbruptSLR

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Re: PIG has calved
« Reply #9 on: July 15, 2013, 03:31:22 AM »
Anne,

While there are a large number of factors that control the rate and volume of glacier ice movement; the only driving force is gravity.

Best,
ASLR
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sidd

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Re: PIG has calved
« Reply #10 on: July 15, 2013, 05:04:55 AM »
Gravity drives, but thermo will not be ignored. After all glacier is fed in accumulation zone through tremendous release and absorption of solar driven latent heat.

For PIG (and others) the ice actually moves by refluxing as well as flow. It melts in the cavity at grounding line from hot CDW influx, the fresh water release goes up as fast as it can along the bottom of ice shelf and _refreezes_ near the seaward edge, so the ice near that edge is actually thicker than further upstream. Then, as we see, the seaward chunk breaks off, and we run the movie again.

This refluxing happens beneath glaciers also.

One of these days in my copious spare time, I shall have to work out the relative magnitudes of flow vs reflux in mass transport. More likely, someone will point out that the calculation has already been done and point me to a reference. I suspect that streamflow is more important, but i dunno yet.

sidd

AbruptSLR

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Re: PIG has calved
« Reply #11 on: July 15, 2013, 04:54:20 PM »
Anne,

As Sidd points out, my simplistic response may not be addressing the heart of your confusion.  His additional remarks about refluxing is particularly relevant to the Pine Island Ice Sheet, PIIS, calving event; because a lot of ice mass melted from the Pine Island Glacier, PIG, and then refroze at the edge of PIIS, where it just calved off.  However, at the risk of adding to your confusion: (a) You need to decide whether PIIS is just a floating extension of PIG or whether it is a seperate feature (ie: is the reflux happen within one body, or from one body to a different body); and (b) You need to decide by "move" do you only mean glacial ice movement, or do you mean ice mass loss (which can also occur not only by calving, but also by such means as: (i) basal melting and discharge; (ii) surface melting [including solar induced or rain induced] and run-off; (iii) wind scour of firn; (iv) sublimation; etc.).  In the way of examples: (a) If you are wondering why mountain glaciers are generally retreating worldwide, it is not because gravity is making them calve into the sea faster; it is because they are thermally melting; (b) If you are wondering why the PIG grounding line is retreating so fast, it is both because of advective melting from warm water, as well as because the flow of the glacial ice is causing the glacier to thin locally, which when it thins enough (both due to gravity flow and thermally induced basal melting) will cause the glacier ice to float thus transforming that portion of the glacier into an ice shelf; or (c) If you are only wondering about why the fracture of the PIIS iceberg calving occurred where it occurred and why it occurred at all, that is a combination of such factors as: ice shelf flow, water movement (including: advection, waves, tides and currents); ice shelf geometry (including the edge thickening due to reflux by refreezing); ice strength; internal stress patterns (including stress concentrations and thermal stresses); land boundary constraints; restraint from sea ice (as we have seen this is small); wind drag (and/or barometric pressure); etc.

As Peter Ellis points out it is possible to overthink such matters; but identifying which action controls the phenomena that you are interested in learning about; can depend on which question you are asking (and I point this out because I think that many seasoned researchers ask themselves questions relevant to the Northern Hemisphere, or to Mountain Glaciers, rather than the Southern Hemisphere ice sheets; which to some degree is why AR4's SLR projections have been proven to be so wrong and also why [before AR6 is issued] many of the AR5 SLR projections to be annouced in Sept 2013 will also be proven to be incorrect) .

Best,
ASLR
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Yuha

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Re: PIG has calved
« Reply #12 on: July 24, 2013, 06:21:24 PM »
There's a new infrared image of the crack from July 14:

http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=81674

I can't really tell if there's been any change during the 6 days.

AbruptSLR

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Re: PIG has calved
« Reply #13 on: August 06, 2013, 04:53:29 PM »
The linked information indicates that as of August 1st the iceberg has not moved significantly (but that in the austal summer researchers will take measurements to see whether the remaining PIG-PIIS ice velocities increase due to the lose of buttressing action from the new iceberg):

http://www.livescience.com/38606-antarctic-iceberg-staying-put.html
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Apocalypse4Real

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Re: PIG has calved
« Reply #14 on: September 13, 2013, 02:42:57 PM »
There is a new piece of research out this week in Science on channelized melting effects on the PIG. See:

Channelized Ice Melting in the Ocean Boundary Layer Beneath Pine Island Glacier, Antarctica

T. P. Stanton1,*,
 W. J. Shaw1,
 M. Truffer2,
 H. F. J. Corr3,
 L. E. Peters4,
 K. L. Riverman4,
 R. Bindschadler5,
 D. M. Holland6,
 S. Anandakrishnan4
 
+ Author Affiliations

1Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943, USA.
2Geophysical Institute, University of Alaska, Fairbanks, AK 99775–7320, USA.
3British Antarctic Survey, Cambridge, CB3OET, UK.
4Department of Geosciences and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802–2711, USA.
5Emeritus Scientist, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
6Department of Mathematics, New York University, NY 10012, USA.
 
↵*Corresponding author. E-mail: stanton@nps.edu
Abstract

Editor's Summary

Ice shelves play a key role in the mass balance of the Antarctic ice sheets by buttressing their seaward-flowing outlet glaciers; however, they are exposed to the underlying ocean and may weaken if ocean thermal forcing increases. An expedition to the ice shelf of the remote Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet that has rapidly thinned and accelerated in recent decades, has been completed. Observations from geophysical surveys and long-term oceanographic instruments deployed down bore holes into the ocean cavity reveal a buoyancy-driven boundary layer within a basal channel that melts the channel apex by 0.06 meter per day, with near-zero melt rates along the flanks of the channel. A complex pattern of such channels is visible throughout the Pine Island Glacier shelf.

AbruptSLR

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Re: PIG has calved
« Reply #15 on: September 13, 2013, 07:59:30 PM »
Thanks A4R,

The following links and commentary related to the research that you cite elaborates on this matter, and the main point of the extract from the following article is that Antarctic Ice Shelves subjected to warm CDW (in this case the PIIS) are less stable than researchers previously thought because the subiceshelf melting occurs non-uniformly, which tends to accelerate the break-up of the ice shelf (as we have recently seen with the major calving in the austral winter of 2013).  This has major implications to the Thwaites Ice Shelf and Ice Tongue:

http://www.scienceworldreport.com/articles/9456/20130913/warm-ocean-water-beneath-antarctic-glacier-melts-ice-unprecedented-rate.htm

"Pine Island Glacier is a major outlet of the West Antarctic Ice Sheet. Yet in recent years, this ice shelf has rapidly thinned and accelerated. That's why researchers decided to take a closer look to see exactly what was causing this increased melting.
The researchers drilled holes in the ice in order to place a variety of instruments there. In addition, the scientists used radar to map the underside of the ice shelf and the bottom of the ocean. This allowed them to see how the ice shelf was melting.
It turns out that the ice is melting more rapidly from below. Why? The oceans are far warmer than they have been in the past, and water can transfer more heat than air. In addition, the terrain beneath the ice shelf consists of a series of channels. The floating ice in the channel has ample room beneath it for ocean water to flow in. The water melts of the ice beneath and cools, but the channels keep the water from staying long enough to become too cold; this, in turn, accelerates melting.
"The way the ocean water is melting the ice shelf is a deeply non-uniform way," said Sridhar Anandakrishnan, one of the researchers, in a news release. "That's going to be more effective in breaking these ice shelves apart.""

The following link leads to the news release cited above:

http://www.eurekalert.org/pub_releases/2013-09/ps-uom091213.php
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LRC1962

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Re: PIG has calved
« Reply #16 on: October 04, 2013, 06:30:39 AM »
Say that report on the channelization. The question I have is this: Do they mean that the ice in those locations are melting 9 times faster then they thought or that they do know how much the melt is and just have found out where the melt is occurring?
With the channelizing being confirmed, I had read in other reports theories of that happening, that would seem to add the the worries about  a faster collapse possible as that would possibly make things 'pop' when it brakes in the middle. What I mean by that is something like what happens if you are pushing against a rock with a stick and the stick brakes in half. The rock, ridge grounding the ice, does not necessarily move, but the force that is behind it certainly does.
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AbruptSLR

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Re: PIG has calved
« Reply #17 on: October 05, 2013, 03:25:52 AM »
LRC 1962

They mean that previously they only had estimates of the average rate of sub-ice-shelf ice melting for the Pine Island Ice Shelf, PIIS, but now that they have direct measurements, they now see that the channelization creates areas with ice melting many times higher than their previous estimates of the average ice melt rate.  Certainly, having higher localized melting zones can weaken the PIIS faster than previously estimated, which can lead to more active/larger calving than previously estimated (as was observed earlier this summer).

Best,
ASLR
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J Cartmill

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Re: PIG has calved
« Reply #18 on: November 10, 2013, 07:08:57 PM »

ggelsrinc

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Re: PIG has calved
« Reply #19 on: November 10, 2013, 08:22:30 PM »
Great animation of PIG at Fairfax Climate watch.

http://www.fairfaxclimatewatch.com/blog/2013/10/pine-island-glacier-pushing-massive-berg.html

Looks like a new crack just upstream of the old one.

http://rapidfire.sci.gsfc.nasa.gov/imagery/subsets/Antarctica_r03c02/2013312/Antarctica_r03c02.2013312.terra.250m.jpg


OK, but I have questions. Notice those cracks are located in the main glacier feed! Has PIG calved off that amount of ice shelf which is moving to the sea or is it still the same cracks I've seen monitored by airplanes flying over it?

It should be obvious, based on your image that the cracks are in the main feed of the glacier behind them. The cracks aren't news and that glacier is watched. Is there evidence to support PIG calving and moving to sea, yes or no?

J Cartmill

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Re: PIG has calved
« Reply #20 on: November 10, 2013, 09:24:11 PM »
My main purpose in posting was to call attention to the FCW blog post and the NASA animation (I've included it here)

The images from the first post in this thread seem to show it has calved.(Also included)

The MODIS image now shows a third crack that just appeared this week.


ggelsrinc

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Re: PIG has calved
« Reply #21 on: November 10, 2013, 10:14:47 PM »
I don't see a difference in your image based on other threads about the ultimate process PIG will face. I'm one of those people who think it's their job to watch glaciers and ice shelves, like they're canaries in my coal mine. The prognosis for PIG is death, but has it happened yet? With my limited knowledge, I think that area is regularly visited by aircraft that would know and I don't see anything on the news about it yet.

Yuha

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Re: PIG has calved
« Reply #22 on: November 12, 2013, 07:22:41 PM »
The ice island is now definitely loose:

werther

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Re: PIG has calved
« Reply #23 on: November 12, 2013, 10:54:46 PM »
Yes Yuha, I just thought to do a late night check on MODIS and saw it happening through thin clouds. I just posted it on the ASIB too.
Action shifting to Antarctica?

AbruptSLR

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Re: PIG has calved
« Reply #24 on: November 14, 2013, 03:51:04 PM »
A nice video from NASA of the direct measurement of sub-iceshelf melting of PIIS can be found at the following website:

http://www.nasa.gov/content/goddard/warm-ocean-rapidly-melting-antarctic-ice-shelf-from-below/

This video also shows the ice velocity of an unnamed glacier (sometimes called the SW Tributary Glacier) feeding ice into the Southwest corner of the Pine Island Ice Shelf, PIIS.  Thus my concern is that as the front of the PIIS continues to thin due to sub-iceshelf melting, it's calving rate will continue to accelerate, which could migrate the calving front back behind the location where the SW Tributary Glacier feeds into the PIIS.  If/when this happens the ice velocity flow rates for the SW Tributary Glacier will accelerate; which in-turn would likely contribute to the destabilization of the Eastern Shear Margin of the Thwaites Glacier; which might then accelerate it's contribution to SLR (in the near-term).
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idunno

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Re: PIG has calved
« Reply #25 on: November 15, 2013, 11:12:02 AM »
Re: PIG has calved

Er, that would be PIG has farrowed; COW has calved.

Unless this is some transspecies Frankenscience experiment going on.

I'll get me coat.

;)

J Cartmill

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Re: PIG has calved
« Reply #26 on: November 15, 2013, 02:05:16 PM »
Matt Owens has a new update at Fairfax climate watch with some inputs from Dr. Richard Alley
http://www.fairfaxclimatewatch.com/blog/2013/11/massive-pig-iceberg-breaks-free.html


High resolution views here:
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=82392

AbruptSLR

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Re: PIG has calved
« Reply #27 on: November 26, 2013, 04:54:28 PM »
While I am not certain, the attached MODIS image from Nov 26th seems to show some local calving from PIIS:
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ggelsrinc

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Re: PIG has calved
« Reply #28 on: November 26, 2013, 06:28:36 PM »
I'd be very interested in a study of historical ice shelves and a documentary of their collapse. I think it speaks without question for what our future will become.

J Cartmill

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AbruptSLR

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Re: PIG has calved
« Reply #30 on: December 10, 2013, 02:10:27 AM »
It appears to me (see Modis image from Dec 9, 2013) that the PIIS is calving small bergy-bit at a faster rate than in the past.  If this is the case, and if this trend continues, then it is possible that in the next few years that the rate of ice flow of the SW-tributary glacier (on the westside of PIIS) could accelerate by a factor of 3 to 6 (based on historical behavior of similar glaciers whose ice shelf buttressing was removed); which in-turn could reduce the stability of the adjoining Thwaites Glacier.
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crandles

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Re: PIG has calved
« Reply #31 on: December 10, 2013, 12:22:34 PM »
Sounds like quite a few ifs there.

Isn't it more likely that these are weaknesses / additional cracks from when the crack worked its way though prior to the calving? Don't we have to wait much longer before such features of the cracking are clearly gone before talking about an increased calving rate?

AbruptSLR

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Re: PIG has calved
« Reply #32 on: December 10, 2013, 04:36:51 PM »
candles,

What level of "proof" one needs before taking action depends a lot on what type of action one intends to take.  The NRC 2013 has already advised policy makers that the risk of abrupt SLR from the WAIS this century is plausible/credible; which should encourage policy makers to adopt a resilency approach to planning for SLR, as a resilency approach does not require a high degree of "proof", as opposed to a 1% probability strength design event which typically requires a higher level of "proof".

While I admit that it is possible that the local calving (indicated by changes in the ice shelf face) could well be due to residual/secondary cracking from the major calving event document at the start of this thread, and that it is possible that the rate of local calving may soon slow-down; however, I believe that it is more likely that the local calving for PIIS will continue to accelerate in the near future for reasons including: (a) the shear boundary of the PIIS is currently more cracked-up and is likely to become more cracked-up as the ice shelf continues to thin, and the ice flow rate continues to accelerate, due to sub-ice shelf melting from the advection of CDW; (b) measurements of the sub-ice shelf melting have demonstrated that this melting is not uniform, resulting in sub-ice shelf grooves/stress-concentrations that promote calving; (c) the changes in the local wind patterns are promoting (measured) increased upwelling induced advection of warm CDW into the ASE; and (d) tidally induced flexure induces more calving of the current thin shelf face than of the former thick shelf face (note that frazil ice slowly accerates to the bottom of the ice shelf near the shelf face, so the major calving removed a thick section of shelf, and the current continued minor/local calving continues to remove thickening sections of shelf).

When one is faced with inherent "deep-uncertainty" one can choose to wait and see what happens (ie procrastinate), or one can choose to take precautionary measures such as establishing an early warning system (as recommended by the NRC 2013 abrupt climate change report), or taking resilency measures against potentially negative consequences.
« Last Edit: December 10, 2013, 10:09:46 PM by AbruptSLR »
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AbruptSLR

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Re: PIG has calved
« Reply #33 on: December 15, 2013, 03:52:01 PM »
The following link leads to an article about research to study how ASE ice shelves have been and continue to lose their grip on the coastlines of the embayment.  Specifically, the accompanying image (from the website) illustrates how rifting (cracking) of the Pine Island Ice Shelf, PIIS, has increased from 1973 to 2011, while comparing the shape of the 2011 calving face with the current calving face (see prior posts in this thread), shows how rapidly the calving has accelerated in the past two years (as compared to the 1973 to 2011 period).  This provides support to my proposal that this trend of increasing cracking will lead to increasing calving of PIIS over the next few years:

http://www.research.gov/research-portal/appmanager/base/desktop;jsessionid=0R22SySYfBp1vN1LFqpJYkZxG4rM6zWMKkTTP6kp1QP47Sk072gQ!-1826466010!941996275?_nfpb=true&_windowLabel=awards_1&_urlType=action&wlpawards_1_id=%2FresearchGov%2FAwardHighlight%2FPublicAffairs%2F23322_WestAntarcticiceshelvesslip-slidingaway.html&wlpawards_1_action=selectAwardDetail
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AbruptSLR

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Re: PIG has calved
« Reply #34 on: December 21, 2013, 03:40:57 PM »
While we may need to wait for the clouds to clear in order to make a definitive statement on this matter, but it appears clear to me from the attached image (from LANCE) comparing the PIIS on Dec 21, 2013 to Dec 19, 2013; that a very significant about of calving has occurred between these dates (primarily on Dec 20) in the area of high rifting that I indicated in my immediately preceding post.

If this observation is correct, this is potentially bad news as this high rifting area appears to contain a large amount of cracks and continued calving of bergy bits may continue throughout this austral summer.  If this were to happen then it is conceivable that the SW Tributary Glacier could lose its buttressing support from the PIIS, and its rate of ice flow could accelerate several times (say 5 times); which should then reduce the stability of the Thwaites Eastern Shear zone.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #35 on: December 21, 2013, 03:51:47 PM »
For those having trouble identifying the area of rifting that I am referring to, it is clearly visible in the upper portion of the attached TerraSAR-X image from July 8, 2013.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Shared Humanity

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Re: PIG has calved
« Reply #36 on: December 21, 2013, 09:25:43 PM »
For those having trouble identifying the area of rifting that I am referring to, it is clearly visible in the upper portion of the attached TerraSAR-X image from July 8, 2013.

Sure looks like the glacier is losing its grip on land. Could that explain the curve in the calving front as well as the two pronounced calving fronts near the rifting?

AbruptSLR

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Re: PIG has calved
« Reply #37 on: December 22, 2013, 12:34:50 AM »
Shared Humanity,

Yes, this pattern of calving is clearly due to shear cracking which is causing the Pine Island Ice Shelf to gradually lose its grip on land.  The attached image comparing the afternoon of Dec 19th to the afternoon of Dec 21, 2013 more clearly shows the recent calving (and where I expect calving to continue during this austral summer).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #38 on: December 22, 2013, 01:09:43 AM »
The attached image comes from NASA's WorldView:

https://earthdata.nasa.gov/labs/worldview/

This image shows a different angle of the site of the calving that occurred on Dec 20, 2013
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #39 on: December 22, 2013, 01:15:15 AM »
For comparison to the Dec 21, 2013 WorldView image in my immediate prior post, accompanying is the same view taken on Dec 19, 2013.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

MOwens

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Re: PIG has calved
« Reply #40 on: December 22, 2013, 01:57:26 AM »
new Google Maps are just out, if you have a Google+ account, you can take a look (I'm pretty sure).

There are some VERY cool features in the maps, including PIG. You can tilt the map, and there is a high-definition view of the entire crack before the berg calved....other features worth seeing are Greenland and Antarctica in general. The tilt feature took a little time to get the hang of, but was otherwise easy.

I posted some screenshots here: http://www.fairfaxclimatewatch.com/blog/2013/12/new-google-maps-makes-getting-lost-fun.html

and here's two from Antarctica:




AbruptSLR

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Re: PIG has calved
« Reply #41 on: December 22, 2013, 06:27:21 PM »
The attached image from LANCE taken on Dec 22, 2013 shows the recent calving area without any cloud cover (as verified by the the infrared image).  This image not only shows the extent of the recent calving, but also shows the adjoining shear cracking that will likely lead to more calving in this area as the austral summer progresses:

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #42 on: December 23, 2013, 03:56:34 AM »
I thought that this Dec 22, 2013 WorldView image of the recent (12/20/13) calving area was worth posting.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #43 on: December 26, 2013, 06:10:52 PM »
It looks to me like snow is being blown off (or is sliding off) of the top of the high shear zone of PIIS into the ocean in this Dec 26 2013 LANCE (Terra) image.  Furthermore, it looks to me like this loss of snow cover is forming a deep long trench in the snow in the high shear zone of PIIS.  In the worst case scenario, as surface temperatures warm during this austral summer, the loss of the insulation from this lost snow cover could potentially accelerate surface ice melting in this cracked-up area which could lead to surface melt water flowing into the local crevasses, which would promote further calving in this sensitive area of PIIS; which in turn could accelerate the flow velocity of the indicated SW Tributary Glacier.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #44 on: December 28, 2013, 02:07:30 AM »
While there is some cloud cover (so the view is not clear), it looks to me that the accompanying Terra (LANCE) image from Dec 27th shows some minor calving in the notch in the Northeast calving face as compared to the Dec 26th image that I posted yesterday.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #45 on: December 30, 2013, 06:44:08 PM »
From the attached image it is not clear whether the new approximately 25km long float ice debris field/tongue and the associated new approximately 30km long trough in the snow above PIIS, is due to a local calving event and/or an avalanche of snow (possibly assisted by wind scour).  Nevertheless, this image shows a large scale dynamic event; which, does not speak well for the stability of the local face of the Pine Island Ice Shelf, PIIS.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

steve s

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Re: PIG has calved
« Reply #46 on: December 30, 2013, 09:12:30 PM »
I suspect the image is of a cloud and shadow cast on a snow and water background..

AbruptSLR

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Re: PIG has calved
« Reply #47 on: January 06, 2014, 01:50:10 AM »
While it is possible that the image that I posted on Dec 30, 2013 may have some cloud cover over the PIIS; it is now my opinion that the approximately 25km streak in the ocean is probably snow blown (scoured) into the ocean by katabatic wind.

The attached image from January 5, 2014 indicates: (a) that between Dec 30th and January 5th there has been a good amount of snowfall over the PIIS, sufficient to fill-in snow blown into the ocean by katabatic wind, but not sufficient to fill-in any trough from an avalanche (therefore I conclude that no avalanche occurred on Dec 30th); and (b) there is clear signs of continued calving in the northeast notch in the PIIS, in the area of high shear cracking, and it is particularly in this area that I am concerned about continued calving throughout the current austral summer:

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #48 on: January 06, 2014, 02:23:28 AM »
In regard to my earlier post today, I thought that some people would like to see the attached infrared Terra image from January 5 2014, indicating that there are no clouds in this area on this date.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Andreas T

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Re: PIG has calved
« Reply #49 on: January 07, 2014, 10:02:58 PM »
There is weather data available from PIG http://efdl_5.cims.nyu.edu/timeseries/NYU_AWS_PIG_timeseries.html
snow depth data looks odd, not sure what that means, could this be caused by snow blown into drift or cleared by wind?