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Author Topic: Filchner-Ronne Ice Shelf  (Read 11361 times)

Grygory

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Filchner-Ronne Ice Shelf
« on: September 12, 2018, 10:13:46 AM »
Further development of the gap in Filchner-Ronne Ice Shelf.With black dots I marked the ends of the crack visible in the pictures. The green dot is likely to increase one of the crack(however, the quality of the images is too low)
« Last Edit: March 25, 2022, 09:39:32 AM by oren »

oren

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #1 on: September 12, 2018, 11:13:35 AM »
Beautiful animation. That crack has certainly accelerated in the last few weeks.
How far is it behind the front?

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #2 on: September 15, 2018, 10:20:16 AM »
Dimensions crack (plus minus 10%

oren

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #3 on: September 15, 2018, 11:18:42 AM »
Thanks Grygory.

Darvince

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #4 on: September 17, 2018, 05:18:04 AM »
How long ago was the last major iceberg to break off of the FRIS?

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #5 on: September 17, 2018, 04:23:18 PM »
Unfortunately, I do not have photos from an earlier period than half a year. Maybe somebody has an older archive because polarview has no archives over a month.
ps.It seems to me that it is not yet an iceberg and it may take a long time before the second edge separates from the glacier. This rift, which has a size of 40km in the photo, started to be visible in the last half-year.-I wonder if this crack will continue to develop or the stress has been discharged.

FrostKing70

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #6 on: September 17, 2018, 05:21:49 PM »
Great pictures!  Any idea if the crack will propagate to the top edge (35 KM), or continue running parallel to the right?   If so, is there a natural termination point for the crack if it continues to the right?

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #7 on: September 17, 2018, 08:46:34 PM »
Great pictures!  Any idea if the crack will propagate to the top edge (35 KM), or continue running parallel to the right?   If so, is there a natural termination point for the crack if it continues to the right?
I think that for a while the crack will stop and later it will grow to the right. These three parallel fissures probably stopped on the same obstacle in the form of stronger ice and it will take some time before it can be defeated-It was the same with this new crack(40km) as it probably went through strong ice and began to grow fast
But these are just my thoughts.(I do not know much). When I find time I will find out if someone who knows something more described it. - Pretty much the same looked for Larsen C the slit stopped every now and then on the strong ice. Unfortunately it is a pity that I could not find photos of the entire FRIS.
-Interesting places are where glaciers start developed ice shelf.In places where ice was passing near obstacles it probably becomes stronger and cracks stop at these places later

maga

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #8 on: September 22, 2018, 01:27:43 PM »
My understanding is also that the rift will propagate parallel to the front but there are also some cracks perpendicular to the front which will split the developing ice berg into parts. As Grygory suggests, and similarly to Larsen C, there are areas in the ice shelf where two ice streams merged (suture zones) which can prevent rift propagation for some time because the ice lost the nicely ordered structure there. Further inhibiting rift propagation at the Ronne ice shelf is bottom accumulation stemming from refreezing supercooled water originating somewhere at greater depth near the grounding line. That can close newly formed rifts again.  However, now we have the left hand side of the ice berg essentially dangling freely and it can move back and forth with the tides etc. It is a huge lever and and should be able to open the rift much faster than before. That was also the case at Larsen C and was the reasoning behind my previous comment about a calving event rather soon. "Soon" in this context may still mean several month to probably a couple of years...

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #9 on: September 26, 2018, 08:07:27 AM »
It seems to me that the right crack is growing - But it's hard to see

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #10 on: September 28, 2018, 07:14:30 PM »
This year Filchner-Ronne ice shelf will be exposed faster to sea waves? - On GIF (if I did not make a mistake, I marked the dominant direction of ice movement in this region) you can see marked sea ice, which protected the shelf from the influence of waves this year is very few and can quickly retreat

source:https://www7320.nrlssc.navy.mil

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #11 on: October 01, 2018, 09:38:43 AM »
It"s still hard to see but in my opinion the crack is heading to the edge. I have marked the outline as if it was a poorly visible outline (which may be a crack) which as if it were continued (stars) goes perfectly into the next crack.-Or maybe it's just an illusion-What do you think ?

source :https://www.polarview.aq/antarctic

ps.the photo has been subjected to several modifications for better contrast in low resolution

IceConcerned

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #12 on: October 11, 2019, 10:32:10 AM »
The cracks appear to extend parallel to the sea front :
link with the side completed for some time already
tentative small cracks linking the two big EW cracks - maybe visual artifacts ?
extension of the cracks link to the NS opening at the middle of the shelf
doubling of the length of the southern crack

All evolutions I spotted are underlined in the image

Shared Humanity

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #13 on: October 11, 2019, 04:31:20 PM »
It"s still hard to see but in my opinion the crack is heading to the edge. I have marked the outline as if it was a poorly visible outline (which may be a crack) which as if it were continued (stars) goes perfectly into the next crack.-Or maybe it's just an illusion-What do you think ?

source :https://www.polarview.aq/antarctic

ps.the photo has been subjected to several modifications for better contrast in low resolution

Not an illusion. As rifts begin to form, they can be snow covered and show up as depressions in the surface. I think this is what you are seeing.

iwantatr8

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #14 on: January 29, 2020, 03:50:41 PM »
Some interesting new developments here a set of new cracks - obvious due to the very sharp edges

https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20200128T062554_018E_S_1.final.jpg

The crack has spread from the edge of the ice shelf to the the major crack in the middle making this section of shelf much more unstable perhaps 60% already cracked through.

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #15 on: May 13, 2021, 11:49:10 AM »
A large iceberg: 172 km x 27.6 km has just broken off the Filchner-Ronne Ice Shelf.

Very large image: 5000x3000, click to enlarge

PS : Surface of the main piece about 4292 km2

PS2: The main part of the small piece (top left) is still 45.5 km2
« Last Edit: May 13, 2021, 12:15:22 PM by paolo »

interstitial

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #16 on: May 14, 2021, 08:42:53 AM »
Wow! I gave up on that ever breaking off a few years ago.

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #17 on: May 14, 2021, 11:28:46 PM »
For those who like to follow icebergs, it has just been named, quite naturally, "A76".

It is currently the largest

oren

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #18 on: May 17, 2021, 02:18:22 AM »
I had to remove a message by Grygory which somehow crashed this thread, I am guessing due to its attachment.  This took some detective work:

Another Iceberg in a Month? Further west, another large rift
 (54 W 77 S)

I also removed two test messages by uniquorn which were somehow posted after this message.

Grygory

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #19 on: May 21, 2021, 09:46:34 PM »
I think this bug was caused by uploading too large an attachment during editing. Adding an attachment that is too large when you first write a post only causes the post to be rejected

The resulting iceberg began to form in 2018
https://forum.arctic-sea-ice.net/index.php/topic,2400.msg232745.html#msg232745https://forum.arctic-sea-ice.net/index .php / topic, 2400.msg232745.html # msg232745
The resulting iceberg began to form in 2018 (A short story for people who don't remember)
https://forum.arctic-sea-ice.net/index.php/topic,2400.msg232745.html#msg232745https://forum.arctic-sea-ice.net/index.php/topic,2400.msg232745. html # msg232745
So long ago that I stopped following developments.
I wonder if there will be another calving in the near future - One iceberg seems to be already formed and is only clinging to the ice shelf. But I wonder if the rest will react to the change in tension

FredBear

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #20 on: May 22, 2021, 05:34:52 AM »
Flicking through Worldview images the previous calving from the western part of the FRIS occurred in the dark after April 7 2000 and before August 26 2000, when the resulting icebergs were moving northwards.
I think the correct place to put the new fracture news is really here (where it can be related to other reports of the ice shelf history) so I append the latest calving (of A76):-

A large iceberg: 172 km x 27.6 km has just broken off the Filchner-Ronne Ice Shelf.


PS : Surface of the main piece about 4292 km2

PS2: The main part of the small piece (top left[right?]) is still 45.5 km2
« Last Edit: May 22, 2021, 05:45:18 AM by FredBear »

1rover1

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #21 on: May 25, 2021, 06:28:50 AM »
Good animation of the calving posted here by the European Space Agency.    https://www.esa.int/ESA_Multimedia/Images/2021/05/A-76_The_world_s_largest_iceberg#.YKZSqfD1MlV.link
 

oren

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #22 on: May 25, 2021, 06:35:37 AM »
Thank you, 1rover1.

Here is the animation itself attached. Click.

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #23 on: May 26, 2021, 09:11:46 PM »
For Grygory or Oren: can we change the title of this thread to "Filchner-Ronne Ice Shelf Discussion", i.e. use it for any discussion concerning this ice shelf?

The first animation, based on the images every 6 days from 13/04 to 13/05, focuses on the rift that had opened inside an old rift, the new rift having given birth to this thread. This new rift had not progressed since January 2019 and remained stable until the image of 01/05, in which it extended much to the west. It remains stable in the following days until the calving of 13/05
To locate the particular area under study the animation is preceded by a global image with the area under study highlighted.

The second animation is based on the images of 07/05 and 13/05 and concerns the break perpendicular to the front (it is also preceded by a global image with the studied area in evidence). You can see that there is nothing on the surface to indicate what is going to happen.

I don't think that the stresses inside this ice shelf are episodic with periods of almost no stress (although there may be occasional surges), but that in the case of this ice shelf the fractures are mainly propagating from below and are not well visible from above. I am not familiar with the literature on this ice shelf and cannot go any further at the moment.

As far as the old rift is concerned, it should not be considered as a current rift, it has since thickened (by snow at the top and by ice formation at the bottom), but only as a point of weakness that can reopen if new tensions are applied to the ice shelf. This is what happened with the new rift, which joined the old rift to the south and then moved upwards to the east.

Click to animate and enlarge.

oren

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #24 on: May 27, 2021, 07:44:14 AM »
For Grygory or Oren: can we change the title of this thread to "Filchner-Ronne Ice Shelf Discussion", i.e. use it for any discussion concerning this ice shelf?
Done.

Stephan

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #25 on: May 27, 2021, 01:44:11 PM »
well done  :)
It is too late just to be concerned about Climate Change

oren

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #26 on: May 27, 2021, 02:06:01 PM »
I've moved some messages here from the "Ronne and Ross" thread and merged the rest elsewhere, to avoid further confusion.

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #27 on: June 09, 2021, 01:16:33 AM »
I would like to put the recent calving into historical context

Information on previous calvings:
> October 1998: east side calving, producing iceberg A-38 with an area of about 5600 km².
> February 2000: calving on the west side, producing iceberg A-43 of a similar size (167x32 km)

To visualise the changes in time of the front I provide three animations using the AVHRR/Modis archives. They show that this calving is part of a normal activity of the Ronne ice shelf, but this does not mean that the next ones will always be in the normal range!

First animation: it contains AVHRR/Modis images from 1993 to 2019, with an average interval of one year between images.
The images contain the surroundings of the front and are preceded by a map of the Ronne ice shelf
The animation slows down during two calvings in 1998 and 2000
1px=1km

Second animation: it contains two cycles:
> first: the images of 22/05/1995, 02/01/2001, 18/12/2007, 30/12/2014 and 13/05/2021 (Sentinel1 image)
> second: only the images of 02/01/2001 and 13/05/2021 to compare the fronts relative to the two calvings of 2000 and 2021.
 By reducing the number of images we zoom in a little : 1px=500m

Third animation : I took all the images of the first one (excluding the map) to which I added the image of 13/05/2021, but I reduced the displayed area by limiting myself to the front, which allowed to zoom in : 1px =312,5m
As for the second animation, there are two cycles: the first with all the images and the second with only the two images of 02/01/2001 and 13/05/2021.

As a precaution, given the volumes of the animations I will post them in three posts.
 
Click to animate

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #28 on: June 09, 2021, 01:20:40 AM »
Second animation

 
Click to animate

and click to enlarge

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #29 on: June 09, 2021, 01:26:26 AM »
Third animation

 
Click to animate

and click to enlarge

paolo

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #30 on: June 21, 2021, 10:53:02 PM »
I had detected the calving of A76 in the Sentinel 1 image of the 13th and there were no Sentinel 1 images of the 12th.
On the internet I found a random image (see the first image posted, Suomi NPP image) composed of the Suomi (Brightness Temperature) images of the 10th, 12th and 15th.  In the image of the 12th the rift had advanced completely to the east, but the orthogonal rift to the front was not yet open or not yet visible.
I never look at these images, but this shows me that when Sentinel1 images are missing and events may have occurred, they must be used!
So afterwards I consulted Worldview and found :
> that in the Suomi image, by enlarging and adjusting the contrast and brightness, the first part of the orthogonal rift could be detected (see the second image posted)
> In the Terra image, the whole orthogonal rift (with the two branches on the front side) was clearly visible and therefore open (and without any modification of the image! see the third posted image)
This confirms that the calving took place on the 12th, but above all that we should not forget these images!

Remark : in these images (Brightness Temperature: Suomi, Terra, ...) one pixel corresponds to 250 m and the rift must be well opened to see it!


Click to enlarge
« Last Edit: June 21, 2021, 11:00:43 PM by paolo »

Tor Bejnar

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Re: Filchner-Ronne Ice Shelf Discussion
« Reply #31 on: November 01, 2021, 07:45:45 PM »
Copernicus EU: https://twitter.com/i/status/1455153612653477890
Quote
Glacial motion of Filchner Ice Shelf in #Antarctica. This 160 km wide river of ice has travelled ~5 km over the last 7 years.
2015-2021 timelapse created using #Sentinel1 #radar images.
Impressive movie
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Often Distant

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Re: Filchner-Ronne Ice Shelf
« Reply #32 on: August 14, 2023, 11:20:59 PM »
A tooth loose.
Though declared emergency, climate change is exploited and exacerbated to keep unsustainable nuisance scooter and nuisance bike EVs obstructing streets across most cities causing climate change skepticism. Carelessly declared child toys in NZ. Terminable batteries explode toxic emissions on expiry.

Often Distant

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Re: Filchner-Ronne Ice Shelf
« Reply #33 on: August 24, 2023, 06:21:52 AM »
As the ice moves one way, cracks extend down the other way below where the face was 9 years ago.

And it looks like a new central crevasse was opening up in the Filchner Ice Shelf near the start of May.
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Often Distant

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Re: Filchner-Ronne Ice Shelf
« Reply #34 on: October 17, 2023, 06:56:27 AM »
The Filchner Ice Shelf appears close to calving. It may calve about 40 years deep, ice older than 100 years, some maybe older than twice that. It could take more than a year, though it seems this season can do it soon. It waits on the weather. The ice is thought about 600m thick. If a calved section is to be as big as Falkland Islands in area, such volume could spread out wide 1m as big as Australia. Ice with an area of 12.5km at 600m thick could spread out at more than 1cm across the surface area of the Earth. This segment is mostly floating on the sea already though.

I attach some animations exploring the situation.

The first gif is of NASA Worldview imagery from 2000 to current. It is low resolution, but 24 years still provides an interesting time lapse. Better detail is available on the original source dates. Some large features are visible such as the chasms widening across tongue segments of Recovery and Slessor glaciers, passing near perpendicular to McCarthy inlet on Berkner Island. Of interest is an area where outlined is what looks like it could effectively be an island the ice moves over. At the start of the gif there is a vague dark indentation in the ice slightly south the same size, which originated from the inlet years earlier. As this feature passes the outlined area it is rotating and the central chasms widen. The coastline layer was derived from 2010 dates. I'm not sure if it was read like a hole in the ice or rock mass on the ice.

Also of note is the ice build up at the point of the touchdown hills , coming down from the slopes of Coats Land at the frontal edge of the shelf at the top of the gif. Sea ice largely holds it in and it is being shunted forward the entire time.

If the ice reduced in thickness 1 or 2 metres per year over 20, it could also have reduced in elevation about 2 or 4 metres over that time. Chasms may not grow as wide for as long as prior to the 1986 calving if the ice elevation is not as high. There is probably not a research station positioned on it this time.

It seems the velocity of the frontal shelf has increased this year which would imply large icebergs may be close to popping out, but alignment in the gif frame is not precise. This won't measure it.
Recovery Glacier feeds into the shelf just to the right of middle at the bottom of the gif. On the right near 80°S, Slessor Glacier comes in near 1km thick. At the top, Bailey Ice Stream wraps down around into the slopes of Coats Land near 1km thick in from the right. Left of Recovery, south beyond the gif is Support Force Glacier, and the Foundation Ice Stream with ice around 1km thick. Much of the ice feed inlets rise well in excess of 100m above sea level.

Near the vicinity of Recovery Glacier, surrounding ice shelf altitudes lower a few hundred metres where velocity increases northward up the Filchner trough. Some of that height may transfer across width and length. If so, it may be that iceberg sections breaking off from the front section, could potentially resort to being effectively 1km thick again through weight distribution.
The Filchner trough runs a channel stretching the entirety of the ice shelf at depths in excess of 1km to seabed and extends out hundreds of kilometres north all the way across to the deep shelf break section of the Weddle Sea. The calving margin is much deeper than most of the Ronne Ice Shelf. Warmer water can flow in under it. High ice can flow into it. Berkner is an ice rise over 800m high. How much can come down from it if the shelf breaks back deep enough to expose the inlet to ocean front?

The second gif is a slower better version to the ugly one in my earlier post above. It displays clearer details though only across December 2017 to December 2022. Of note is the ice flow out from the McCarthy Inlet. The flow momentum from the inlet is slow in comparison to the flow of the Filchner ice shelf. It is largely disjointed with the discharge of McCarthy ice mass. Velocity flow transition lines appear to be expanding into cracks toward the front. Also of note is the protective fast sea ice top right.

The next 2 gifs focus in on smaller ice streams across on Coats Land mass on the eastern side at the frontal calving margin. Both seem to be slipping away. The first one comes down at Touchdown Hills and interacts with the Filchner shelf terminus at what now seems a slipping pinning point, and the second gif is Lerchenfeld Ice Stream, positioned slightly further north east. The ice shelf momentum is pushing upon it all. The ocean is pulling much of it loose. Perhaps it can shake the big stuff out soon too.
« Last Edit: October 17, 2023, 08:22:09 AM by Often Distant »
Though declared emergency, climate change is exploited and exacerbated to keep unsustainable nuisance scooter and nuisance bike EVs obstructing streets across most cities causing climate change skepticism. Carelessly declared child toys in NZ. Terminable batteries explode toxic emissions on expiry.

Often Distant

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Re: Filchner-Ronne Ice Shelf
« Reply #35 on: October 17, 2023, 07:11:29 AM »
I attach some close up gifs using sentinel optimised natural colour.

The first one is another look at the eastern front and the touchdown hills ice flow.

The second focuses in on the western front, moving further south in the next couple focusing on visible features from the outflow of McCarthy Inlet. It is interesting the ice flow seen expanding out down from the edges of Berkner Island where exposed to the ocean at the calving front.
Though declared emergency, climate change is exploited and exacerbated to keep unsustainable nuisance scooter and nuisance bike EVs obstructing streets across most cities causing climate change skepticism. Carelessly declared child toys in NZ. Terminable batteries explode toxic emissions on expiry.

oren

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Re: Filchner-Ronne Ice Shelf
« Reply #36 on: October 18, 2023, 01:03:38 PM »
Thank you, OfD, for these long term animations.
As usual, I am attaching an overview map of the F-R ice shelf, along with the main tributaries (codes explained in the caption).



Figure 1. Map showing the Filchner–Ronne Ice Shelf and adjoining ice streams. Circular markers show locations of GPS sites and are coloured according to Msf amplitude. The background colour map shows ice speed, grounding lines are indicated by solid black lines and dashed contour lines show tidal range (in metres). Acronyms for glaciological features marked on the map are as follows: Evans Ice Stream (EIS), Talutis Ice Stream (TIS), Rutford Ice Stream (RuIS), Institute Ice Stream (IIS), Moller Ice Stream (MIS), Foundation Ice Stream (FIS), Support Force Glacier (SFG), Recovery Ice Stream (ReIS), Slessor Ice Stream (SES), Hemmen Ice Rise (HeIR), Korff Ice Rise (KIR), Kershaw Ice Rumples (KeIR), Doake Ice Rumples (DIR) and Henry Ice Rise (HIR).


From: Rosier, Sebastian & Gudmundsson, Gudmundur. (2020). Exploring mechanisms responsible for tidal modulation in flow of the Filchner–Ronne Ice Shelf. The Cryosphere. 14. 17-37. 10.5194/tc-14-17-2020.

oren

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Re: Filchner-Ronne Ice Shelf
« Reply #37 on: October 18, 2023, 01:07:07 PM »
And another which might be clearer.


Often Distant

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Re: Filchner-Ronne Ice Shelf
« Reply #38 on: October 21, 2023, 12:58:59 AM »
A few more animations. The Ronne Ice Shelf looks to be weakening across the central segment toward the calving front. Notable in the first couple of gifs is how much mass has been coming down from Berkner Island in recent years. It is not as high as it was. The third gif is far across at the western edge of Ronne Ice Shelf where glaciers meet at the calving margin.

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Re: Filchner-Ronne Ice Shelf
« Reply #39 on: October 21, 2023, 09:10:07 AM »
Does one of those images show height?

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Re: Filchner-Ronne Ice Shelf
« Reply #40 on: October 22, 2023, 10:39:33 AM »
Quote
Does one of those images show height?

Barely. As an image one can't show height, but maybe as an animation it can to a degree. They can't measure it but they show it changing. Better resolution images are available going back to the dates on the satellite data. The images don't display a lot of what can sometimes be seen such as when ice has the appearance of tree rings and wood splits in the annual layers of compressed snow. Clues to gradients appear through clear light and shadow, and air pressure and cloud formations and cloud shadows, and water flow paths. Comparative data is limited to tiny time span and is understudied. 

I think the first gif on #38 may show the eastward pressure from the Ronne Ice Shelf is rippling through Berkner, buckling the northern portion around eastward into Filchner to perhaps have caused the chasms and rifts and inlets. Height may have changed about 20m during the span of the gif. Berkner seems interactive to the cracks appearing about 80km deep in the Ronne Ice Shelf in 2021. Calvings at the point of Berkner Ice Rise seem to carry potential to trigger massive situations that could quickly bring apart much of the ice shelves and bring down much of Berkner and bring up the oceans. It sits near sea level on the northern front and seems it could be on a slide to coincide with the crumbling of the northern shelf ice either side. Dynamics are shifting away from slow. It can make up lost time.

Current estimates put Berkner at 869m. Estimates 40 years ago put it near 1,000m. Perhaps the differences in height estimates are somewhat result of timespan elapse rather than discrepancies in measurement.

From 2017:
Quote
"Berkner Island was surveyed as part of the Filchner-Ronne Ice Shelf Programme in 1985–86 along flight tracks totalling 1600 km. From these data, contour maps of bedrock and surface elevation were produced (Figs 4 and 5). The most interesting evidence from the surface elevations is that Berkner Island is divided into two summit areas: a southern summit with a maximum elevation of 940 m and a northern summit with a maximum elevation of 730 m. Maximum calculated ice thicknesses are 1100 m for the southern part and 940 m for the northern part."
https://www.cambridge.org/core/journals/annals-of-glaciology/article/ice-thickness-and-bedrock-elevation-in-western-neuschwabenland-and-berkner-island-antarctica/4334AC4077E9687DBDE77ADFE7A53E04

From 2017:
Quote
"Roughly kidney-shaped, it rises to two domes approximately 140 km apart: Reinwarthhöhe in the north at 720m a.s.l., and Thyssenhöhe in the south at 890 m, separated by a trough, the McCarthy Inlet."
https://www.cambridge.org/core/journals/annals-of-glaciology/article/1000-year-icecore-records-from-berkner-island-antarctica/D7C26F0DCEA98746F42336735864FA0E
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Re: Filchner-Ronne Ice Shelf
« Reply #41 on: October 23, 2023, 01:15:29 AM »
At near 80°S, Slessor glacier tends largely east to west occupying a short trough near 2km deep extending around 100km in the confines of a valley section forged between the mountains of the Shakleton Range to the south and Theron Mountains to the north. The depths don't continue into the Filchner trough. Before joining the northward momentum of the Filchner trough, flow veers toward the south as bedrock becomes half as shallow at steep gradient. Inflow feed into Slessor is a chaotic squeeze. Ice flow enters sharply from vastly differing directions, and twists around in differing directions at different heights and depths and layers.

Higher ice long ago used to flow through at differing angles somewhat determined by, and somewhat determining the land mass distribution. Ice at different points at different times can be collecting matter, mineral or organic, fresh or fossil and carrying, or dispersing it quickly or slowly. Ice at different layers pushes in differing directions. Ice presses downward at points and ice lifts upward at points. It twists and turns and grinds and breaks. Water streams through and under different sections at different rates depending on temperatures, ice mass volume and velocity flow interaction to Earth mass. It seems that flow into Slessor Glacier had long earlier reduced and brought the ice elevation down enough to cause the bordering ice mass to spill heavy load across from above, raising the elevation back up.

The first animation is of NASA Worldview imagery from 2000 to 2023. With the wedge at the top middle half of the gif where a portion of the Theron Mountains is slightly visible on the left, land mass is submerged by very slow ice, much of which is perhaps hundreds of metres thick, with much of it reaching in excess of 1km high. It seems to be an ice rise largely held in place due to the counter momentum of slow flowing ice compacting up around against it. At the point of the ice deformations against it on the right, ice squeezes in on outer layers of the ice rise. It is becoming quite active with large displacement seen spilling south onto and into Slessor, near where the glacier runs a gradient down another couple of hundred metres to the Filchner Ice Shelf. The northern segment of the glacier is covered in similar such bulging thick ice all the way down through confining convergence with Bailey Ice Stream, where the sharp natural angle points. It is heavily constrained through bathymetry and counter flowing ice, having not gained access into the deep Filchner Trough like the more western veering lower Slessor segment.

The collecting thick bulging ice sector seems near motionless but may be building up toward potential velocity increase that could flow along across the top of Filchner in an avalanche pulling loads of continental ice mass down a new ice stream. If it gets thick enough along direct connecting gradient trajectory path between points low elevation west and high elevation east, ice can potentially swing down with the forces of gravity over the top from northward on the east and veering northward on the west cutting across the Bailey Ice Stream. Or if ice at the high point of Slessor continues to build up thick enough, ice could spill down on top of the main less restrained glacial bend to veer around more south, and westward. What could take decades, could take years. It's largely wait and see on how large weight on seas will be.

The second animation is zoomed out a bit further and has more spaced out dates. The third gif shows various times over 5 years with Sentinel 2L1C NDWI trying to get a rough view of bulging ice dynamic. The forth gif is further north with Bailey Ice Stream on the right. It compares two Sentinel 1, EW-HHHV images about 5 years apart. The pressure load is building out of shot to the lower right. Filcher crevices begin deeper south. Elevation seems to be lowering. Watch that space.
« Last Edit: October 23, 2023, 01:51:35 AM by Often Distant »
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Re: Filchner-Ronne Ice Shelf
« Reply #42 on: October 23, 2023, 04:40:33 AM »
 I wondered if the post below was saying that one of the images showed height. Apparently that is not what you were saying.


An image can use false color to show height but it must be measured. Implying height from satellite images even over time is not vary accurate or reliable.   


A few more animations. The Ronne Ice Shelf looks to be weakening across the central segment toward the calving front. Notable in the first couple of gifs is how much mass has been coming down from Berkner Island in recent years. It is not as high as it was. The third gif is far across at the western edge of Ronne Ice Shelf where glaciers meet at the calving margin.
« Last Edit: October 23, 2023, 04:49:41 AM by interstitial »

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Re: Filchner-Ronne Ice Shelf
« Reply #43 on: October 23, 2023, 06:45:46 AM »
Satellite images show mass loss coming down from the northern section of Berkner Island, which used to be much higher in the past. Oceans are higher than they were and they are going to rise.

Accurate comparable measurements of elevation changes over extended time with high resolution data would be useful to monitor for tsunami risk. Best done not from being in those waters and not from being on the ice shelves and not from being on the ice rise either. The area (as are others) is very near dramatic tipping points that won't be slow.

Not much can be seen from gifs.
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Re: Filchner-Ronne Ice Shelf
« Reply #44 on: October 24, 2023, 05:49:55 AM »
There is a satellite that measures actual elevation, I think it is IceSat? I wonder if data can be found that compares elevations over time of FR ice shelf and its tributaries.

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Re: Filchner-Ronne Ice Shelf
« Reply #45 on: October 27, 2023, 07:39:56 AM »
A long duration animation of Ronne Ice Shelf at the point of Berkner Island. It spans 2014 to present with a slight pause where 2016 is missing, and another where the satellite imagery alignment alters in 2020. It's otherwise largely aligned and is quite interesting to watch.

It looks like a finger or a sore thumb has a grip on the shelf from below through the bed rock and the island, but it's stretching out and wrinkling with age and turning somewhat into wet sand. The fingernail looks like it could shrink down to dust by 2030 if the surrounding ice shelf can hang on that long. It seems like the surrounding shelf ice is not intending to hold out that long.
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