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Author Topic: Pine Island Glacier (PIG) Calving and Discussion  (Read 738256 times)

KiwiGriff

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1750 on: February 11, 2020, 07:31:34 PM »
 The relative size of the ice to the water it needs to displace is significant.

Eureka.
The water you need to displace is one to one to the volume of ice under the water. Same mass according to Archimedes.
You would also see significant eddying around the perimeters if the forces of tension from the calving were responsible for the movement. I see mostly  uniform movement rather than the chaos you would expect from internal forces acting at different vectors.
Animals can be driven crazy by placing too many in too small a pen. Homo sapiens is the only animal that voluntarily does this to himself.
Notebooks of Lazarus Long.
Robert Heinlein.

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1751 on: February 11, 2020, 07:54:17 PM »
The relative size of the ice to the water it needs to displace is significant.

Eureka.
The water you need to displace is one to one to the volume of ice under the water. Same mass according to Archimedes.
You would also see significant eddying around the perimeters if the forces of tension from the calving were responsible for the movement. I see mostly  uniform movement rather than the chaos you would expect from internal forces acting at different vectors.
If a 100km iceberg moves 10km, how much water is displaced relative to the size/mass of the ice?  Not 100%!

RoxTheGeologist

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1752 on: February 11, 2020, 08:02:49 PM »
The relative size of the ice to the water it needs to displace is significant.

Eureka.
The water you need to displace is one to one to the volume of ice under the water. Same mass according to Archimedes.
You would also see significant eddying around the perimeters if the forces of tension from the calving were responsible for the movement. I see mostly  uniform movement rather than the chaos you would expect from internal forces acting at different vectors.


If a 100km iceberg moves 10km, how much water is displaced relative to the size/mass of the ice?  Not 100%!

100% of the mass if the ice is floating, size wise its Volume*(density of freshwater)/(density of seawater).


KiwiGriff

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1753 on: February 11, 2020, 08:24:12 PM »
If a 100km iceberg moves 10km, how much water is displaced relative to the size/mass of the ice?  Not 100%!

The amount of water displaced will be equal to the distance moved times the volume of the iceberg under water.
Animals can be driven crazy by placing too many in too small a pen. Homo sapiens is the only animal that voluntarily does this to himself.
Notebooks of Lazarus Long.
Robert Heinlein.

Tor Bejnar

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1754 on: February 11, 2020, 09:07:59 PM »
For the more casual viewer, here is a Polar View location map of Pine Island Glacier (PIG) and Pine Island Ice Shelf (PIIS) [orange circle added] and a piece of the highlighted radar image from this 3:47 am image and a later radar image (4:35 am)

See how much (little) movement there was in 45 minutes.

PS: the glacier is about 50 km wide.
« Last Edit: February 11, 2020, 09:57:36 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

KiwiGriff

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1755 on: February 11, 2020, 09:21:39 PM »
Silly boy you are not talking sense Griff .
The volume moved will be due to the displacement of water not the volume of the berg .
Still an incredible amount of water and any one who has messed around in boats will know that any force applied to an object immersed in water is quickly dissipated. I  can not see any force of tension being applicable to the movement soon after the ice fractured it would all be transferred into the surrounding water. Wind is not going to be the overriding effect either the overall movement must be due to underlying currents.
Animals can be driven crazy by placing too many in too small a pen. Homo sapiens is the only animal that voluntarily does this to himself.
Notebooks of Lazarus Long.
Robert Heinlein.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1756 on: February 11, 2020, 10:10:38 PM »
The Sentinel2 image is not so bad and my previous post work (post 1744) was correct. Actually the pictures of the day are really necessary? ::) :D ;)
Attached the image of the day, for text and notations see post 1744 and its image
« Last Edit: February 11, 2020, 10:23:58 PM by paolo »

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1757 on: February 11, 2020, 10:23:04 PM »
I do not have time and it seems to me that there is nothing particular to report except that we see a small extension for ex rift 3, i.e. exR3 and that on the SWT side there is a fracture not far from calving.

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1758 on: February 12, 2020, 07:28:40 AM »
Ice drift update.

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1759 on: February 12, 2020, 07:34:32 AM »
What's baffling to me is that this one is still sticking together and not drifting apart.

Edit: I just realized it cracked since yesterday once more. But not drifting apart. Even more baffling.  ???
« Last Edit: February 12, 2020, 07:41:39 AM by blumenkraft »

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1760 on: February 12, 2020, 08:05:45 AM »
Blumenkraft,
while looking at your picture I realized that the 11/02 between the Sentinel1 and the Sentinel2 picture there had been changes ! :o
Two new rifts crossing each other

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1761 on: February 12, 2020, 08:41:27 AM »
In yesterday's Sentinel1 and Sentinel2 images we see a new rift in SIS on the SWT side. It's not good at all. >:( :'(

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1762 on: February 12, 2020, 08:50:38 AM »
Two new rifts crossing each other

Indeed! So why is it cracking but not drifting apart (yet)? I don't get that!

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1763 on: February 12, 2020, 08:52:20 AM »
new rift in SIS on the SWT side.

This is before the pinning point, isn't it?

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1764 on: February 12, 2020, 09:17:51 AM »
On the calving front I have just seen a new fracture which will be added to the existing fractures: exR1, exR2 and exR3.
Clearly the calving front is not at all stable and it is difficult to predict what the final result will be in a few months.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1765 on: February 12, 2020, 09:38:45 AM »
Blumenkraft,

Attached a less zoomed image to position the new SIS fracture

Regarding the fact that the two pieces did not move away from each other I understand your astonishment and as much as the pieces created by the new rifts in less than 12 hours of their opening (the two images before and after opening being of the same day) are more distant.
But you have to take into account the movements printed by the currents that they can move the pieces further apart, but they can also bring them closer together or leave them in their relative position. The movement printed during calving is of short duration.

Translated with www.DeepL.com/Translator (free version)

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1766 on: February 12, 2020, 09:50:01 AM »
No Sentinel1 images for today, at least for now. >:(
But there was some work behind on yesterday's imagery... ;)

FredBear

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1767 on: February 12, 2020, 12:21:46 PM »
What often drives icebergs away from each other are pieces breaking off between them, especially if the bits topple over and continue to break up. Can be seen in many videos of toppling 'bergs and also may have been a factor in the widening rifts seen earlier in Pine Island Glacier.
Of course, the lower-density water from the underside melting of the glacier by warm, deep water will also tend to float up the fractures as it moves away from the face of the glacier, and may help propel the icebergs too.

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1768 on: February 12, 2020, 02:14:53 PM »
New radar!

Still sticky.

Notice the grounded iceberg upper left.

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1769 on: February 12, 2020, 02:33:22 PM »
There is way less action in the zone of destruction (yet) than i anticipated.

oren

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1770 on: February 12, 2020, 02:37:34 PM »
The PIG and the SWT are now officially and completely detached and unaffected by each other anymore (except by their mutual effect on the waters of the bay).
I wonder how much acceleration we might see in either/both, and how soon it will materialize.

bluice

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1771 on: February 12, 2020, 03:22:19 PM »
What is keeping the ZOD mush in place? Currents or grounding?

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1772 on: February 12, 2020, 03:34:24 PM »
It's still frozen together, Bluice.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1773 on: February 12, 2020, 03:56:52 PM »
Bitter laughter  :(
The calving front has receded so far that today's Sentinel1 image no longer gives any information. Attached last image

Personal Calving Analysis :

1) FredBear, I completely agree with what you're saying. The CDW goes in deep and to the north and after melting the shelf on the grounding line comes out below the ice shelf (with some residual melting in passing) to the south. This water is less dense and tends to rise and enlarge existing fractures if possible. Moreover it is this action that explains the explosive widening of the whole fracture system in the last few months and the final increment in the speed of the southern edge of the calving line already observed in November (more than 6km per year, even with the action of the cork).

2) Concerning the calving I find that there have been mainly three places where there has been a relaxation of tensions:
  a.   North: abrupt opening of two fractures extending an existing fracture to the south and     north, respective lengths: 2.5 km and 1 km.
  b.   South: opening of a much shorter fracture (200m)
  c.   In the center: opening of the two fractures north and south of the ridge already indicated in my previous posts (it is the cigar that was isolated in the center and later divided into three pieces). These fractures are very long: 8km each.
Since the energies released depend on the conditions we do not control (what are the current tensions? is the ice already partially fractured? etc.) we cannot make relative evaluations. Nevertheless these energies are the product of the energy per unit length multiplied by the length of the fracture. We can therefore assume that the energy has been released especially in the centre and north.
As regards their release I think that the first one triggered a shock (earthquake) which propagated to the whole iceberg by triggering the whole rupture. The calving must have been, in my opinion, very brutal and very fast (between one rupture and the other the interval being very short).

3) Currents: in addition to the current exiting to the south (see point 2) there is a clockwise current flowing in front of the calving line. This current has reorganized itself very quickly as it moves up to the new calving line. The two currents: outgoing and circulatory, explain the movements that occur after calving.

Translated with www.DeepL.com/Translator (free version)

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1774 on: February 12, 2020, 04:42:25 PM »
There is way less action in the zone of destruction (yet) than i anticipated.
It's a glacier.  It moves . . . like a glacier.

If you are an action junkie, you are in the wrong place.  ;)

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1775 on: February 12, 2020, 04:49:10 PM »
Oren,
The situation is catastrophic for both. Quick personal forecast for the next few months and to be refined later :

PIG (MIS): Calving is not finished, the calving line has yet to stabilize and it will recede especially in the South. The southern front (in front of the mix) is not stable and the two points (corresponding to the current calving line and the marginal rift later in the heights are not stable at all). The few icebergs still attached to the SIS have extremely weak attachments and will be swept away. As for the mix, it can only go out to sea.
In the next few months we will see the new calving fracture appear: calving late 2021 or 2022, but it will be much further north of the current calving line.
Conclusions: it looks very bad

SWT: it is no longer countered by the MIS and there is no longer any compulsion to change direction, so we can expect it to take an ENE direction that conflicts with the SIS (see on this subject also the new fracture that has appeared in the SIS, which I reported in a previous post). In SW the inking with ice rumples has the days counted, the ice rumples are disintegrating (even if it will take time because of the grounding points). Further upstream from the ice rumples a fracture zone is widening. We can expect a retreat of the SWT calving line.
The grounding line is approaching the inversion point (if not already joined) and the track for CDW will open towards the Thwaites. The end of the heavy stress with the MIS will increase the speed of the SWT and thus decrease its thickness and thus make the grounding line move backwards ...
Conclusions: it looks very bad

SIS (part between MIS and SWT: see how it will react, but the new fracture that has appeared (see previous point), does not promise anything good.

I'm sorry, but I don't see anything that will put our minds at rest...

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1776 on: February 12, 2020, 04:56:05 PM »
It's a glacier.  It moves . . . like a glacier.

Nah, the melange is only in the broughtest of senses still part of the glacier. :P

But seriously, i expected it to float out rather ... immediately.

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1777 on: February 12, 2020, 05:03:17 PM »
Blumenkraft, immediately with the times of a glacier

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1778 on: February 12, 2020, 05:11:40 PM »
I see! :)

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1779 on: February 12, 2020, 05:19:31 PM »
Baking,
After analysis it could be that the trigger was the cigar (see previous post). Regarding the tensions at this point we can take into account the bending of the iceberg induced by the anchorage to the north and the advance to the south and the fact that it was the more rigid point (major thickening) of the iceberg.

You see, I can change my opinion ... ::) ;)

Steven

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1780 on: February 12, 2020, 07:48:40 PM »
From Stef Lhermitte on twitter:  an animation showing the retreat of the PIG calving front from 1973 to 2020, including the calving that happened a few days ago:

https://twitter.com/StefLhermitte/status/1227343805378125824



baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1781 on: February 12, 2020, 08:11:41 PM »
Just for comparison, here is my 2-3 year prediction from November 19 (bottom of page 23 in this thread):

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1782 on: February 12, 2020, 08:31:16 PM »
Yes, but not in 2/3 years, now we are almost there and once the calving line is stabilized (in a few months) we will be there. >:(  Edit: Even further east  >:( >:( >:(
In two years we may be more further east...   >:( >:( >:(
« Last Edit: February 12, 2020, 09:03:07 PM by paolo »

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1783 on: February 12, 2020, 09:25:16 PM »
FYI: I've just seen that Sentinel1 has released another image (low resolution) showing the current calving line
But we don't see much  :(

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1784 on: February 12, 2020, 09:59:51 PM »
As an exercise I wanted to draw three lines for the calving front in August/November: optimistic hypothesis (one can dream), realistic hypothesis and pessimistic hypothesis (one can have nightmares).

NB: I did not take into account the movement of the glacier (about 2/3km).

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1785 on: February 12, 2020, 10:33:39 PM »
Thanks again to all of you for your pictures and animations.
By analyzing the NW tip (ice rumples) of SWT I noticed that the triangular grounded berg, derived from the minor calving around Christmas has disappeared. Was it washed away by the wave action from the great calving? It sat there without any movement for around five weeks.
It is too late just to be concerned about Climate Change

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1786 on: February 12, 2020, 10:55:48 PM »
Analysis of Cork II and its surroundings.

Cork II acts at the moment as a cork by holding back the ice mélange upstream. It is connected with two icebergs to its northeast (blue circled), so the gap between the outer iceberg and the point is only 500 m wide (yellow double arrow) - too narrow for all the icebergs waiting to be exported.
Cork II itself is tied to the SIS, but this connection has weakened. The rift has grown since Jan 06 (light green lines), and other new rifts and cracks have formed or lengthened (light green lines).
The dashed pale magenta line divides the movement directions. SW of it (SIS and SWT) slowly move in NNE direction, whereas the zone of destruction and the point (and the MIS) move fast in NW/WNW direction (pale magenta arrows). This different speed and direction was clearly responsible for the situation in the zone of destruction. It all depends now on the stability of Cork II. When it loses its contact with the SIS, it will become an iceberg moving into Pine Island Bay, followed by the ice mélange. There is no Cork III available to hold it back...

See attached picture.
It is too late just to be concerned about Climate Change

grixm

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1787 on: February 13, 2020, 09:33:41 AM »
The iceberg(s) are hardly even recognizable anymore.


blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1788 on: February 13, 2020, 10:54:57 AM »
Focusing on the zone of destruction.
« Last Edit: February 13, 2020, 11:27:41 AM by blumenkraft »

paolo

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1789 on: February 13, 2020, 06:21:33 PM »
Yesterday I announced the new fracture in the SIS on the SWT side, but I used the Sentinel1 image (which does not have the resolution of the Sentinel2) and the Sentinel2 image of 11/02 (low quality because of the clouds).
I stupidly forgot that we could use the Sentinel2 image of 01/02.
So you'll find attached a zoom with a quality worthy of this forum
Its length is remarkable (~5km, even if with discontinuities: parallel fractures) and possible extensions appear on both sides.
For the positioning see my previous post

EDIT : Stephan,
Excuse me, but the Cork2 is a piece of junk, not only is its base narrow and already well fractured, but the fulcrum (the SIS) is not stable at all ...  ;)


Edit2 : But in today's PIG, where can we find stable points?  ::)

Click to zoom in

Translated with www.DeepL.com/Translator (free version)
« Last Edit: February 13, 2020, 06:40:26 PM by paolo »

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1790 on: February 13, 2020, 07:03:21 PM »
EDIT : Stephan,
Excuse me, but the Cork2 is a piece of junk, not only is its base narrow and already well fractured, but the fulcrum (the SIS) is not stable at all ...  ;)


Edit2 : But in today's PIG, where can we find stable points?  ::)
paolo,
I completely agree. Nevertheless, as long as Cork II (and the remainders of Cork) are present and joint to the SIS, there is no way out for all the icebergs in the "zone of destruction".
It is too late just to be concerned about Climate Change

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1791 on: February 13, 2020, 08:12:06 PM »
Well, Stephan, a lot of small ones can escape, even if it stays in place. There is an opening between it and 'The Point'.

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1792 on: February 13, 2020, 10:32:22 PM »
But this gap is at the very N end of the zone of destruction, not directly in the way the current flows. And it is too narrow for most of the icebergs.
Let's wait and see what happens the next days between the extension of Cork II and the Point.
It is too late just to be concerned about Climate Change

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1793 on: February 13, 2020, 10:38:10 PM »
So, Stephan. Our cork tracking is beginning. ;)
At the moment he is easily identifyable - short way behind the iceberg resulting from the SWT calving. We should follow his track - he deserves it.

PS: And my attention will be paid equally to Cork II, if he once (?) soon (?) will become an iceberg.
It is too late just to be concerned about Climate Change

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1794 on: February 14, 2020, 10:57:12 AM »
On it, Stephan! :)

In other news, the ZOD lost another small piece today.

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1795 on: February 14, 2020, 11:15:58 AM »
Update on the blumencrack area.

Something is not right here.

baking

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1796 on: February 14, 2020, 03:24:55 PM »
Update on the blumencrack area.

Something is not right here.
In the top of the GIF you can see just the bottom of the "blumencrack" and in the bottom is normal shear margin rifting (caused by higher ice velocity in which the rifting brings about a positive feedback loop.)

So I assume you are referring to the cracks spreading into edge of the stationary ice shelf near the center of the GIF?

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1797 on: February 14, 2020, 03:48:28 PM »
You are absolutely right, Baking. Sorry for being imprecise.

Do you think those (in the middle of this GIF) are related to the blumencracks or are they indicating different forces causing them? Or better to say, are the blumencracks also a function of the ice sheet flowing faster?

Stephan

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1798 on: February 14, 2020, 05:32:51 PM »
In my opinion these blumencracks are nothing else than a preparation of a new zone of destruction which will reach the calving front within a year (?, just a guess, not calculated). It will then decrease the contact to the solid ice on the NE side of PIIS-MIS, lead to a higher flow velocity and facilitate further calving.
We must watch them.
It is too late just to be concerned about Climate Change

blumenkraft

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #1799 on: February 14, 2020, 05:58:51 PM »
But, Stephan, the blumencracks are pretty out of the floating ice area. Do you really think they are caused by the flowing of the ice sheet also?