Filchner-Ronne Ice Shelf

[Grygory]

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)

[oren]

Beautiful animation. That crack has certainly accelerated in the last few weeks.
How far is it behind the front?

[Grygory]

Dimensions crack (plus minus 10%

[oren]

Thanks Grygory.

[Darvince]

How long ago was the last major iceberg to break off of the FRIS?

[Grygory]

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]

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]

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]

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]

It seems to me that the right crack is growing - But it's hard to see

[Grygory]

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]

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]

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]

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]

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]

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

[interstitial]

Wow! I gave up on that ever breaking off a few years ago.

[paolo]

For those who like to follow icebergs, it has just been named, quite naturally, "A76".

It is currently the largest

[oren]

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]

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]

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

[1rover1]

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]

Thank you, 1rover1.

Here is the animation itself attached. Click.

[paolo]

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]

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]

well done 

[oren]

I've moved some messages here from the "Ronne and Ross" thread and merged the rest elsewhere, to avoid further confusion.

[paolo]

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]

Second animation

 
Click to animate

and click to enlarge

[paolo]

Third animation

 
Click to animate

and click to enlarge

[paolo]

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

[Tor Bejnar]

Copernicus EU: https://twitter.com/i/status/1455153612653477890

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