Arctic Sea Ice : Forum

Cryosphere => Antarctica => Topic started by: charles_oil on January 16, 2017, 06:30:16 PM

Title: Halley base shut down and new crack in Brunt shelf
Post by: charles_oil on January 16, 2017, 06:30:16 PM

The British Antarctic Survey is to pull all staff out of its space-age Halley base in March for safety reasons.
The highly unusual move is necessary because the Brunt Ice Shelf on which the research station sits has developed a big new crack.

http://www.bbc.com/news/science-environment-38643420 (http://www.bbc.com/news/science-environment-38643420)

Lets hope it can get fixed !
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FredBear on January 16, 2017, 10:41:04 PM
Oops, sometimes things move faster than expected! Good idea to give Halley VI skis - but is it water-proof and will it float?
I see the "Halloween Crack" has doubled in length (to 44km) between 31 Oct and 10 Jan, while the original Chasm 1 was only growing at 1.7km per year. BAS not sure where, when or what calving will take place so justplaying safe!
It sounds as if originally the plan was to finish the move by the end of next season (2017-18) but this looks like Halley VIa will have to be ready for the start of that season?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Tor Bejnar on January 17, 2017, 12:17:05 AM
from the BBC article:

http://www.bbc.co.uk/news/science-environment-38643420 (http://www.bbc.co.uk/news/science-environment-38643420)
[/quote]
Quote
Ice crack to put UK Antarctic base in shut-down

The British Antarctic Survey is to pull all staff out of its space-age Halley base in March for safety reasons.

The highly unusual move is necessary because the Brunt Ice Shelf on which the research station sits has developed a big new crack.

BAS officials say neither staff nor the base are in any immediate danger but believe it would be prudent to withdraw while the situation is assessed.

The plan would be to go back once the Antarctic winter is over, in November.

Unpredictable situation

BAS is in the process of conducting such a move right now. The relocation is all but complete, with the last pod currently in the final stage of being shifted 23km to the new site.

The move was necessitated by a chasm that had opened up in the shelf and which threatened to cut off Halley. But this huge fissure to the west of the station is not the cause of the temporary closure.

Rather, it is another break in the ice some 17km to the north and east of the new base position. It has been dubbed the "Halloween Crack" because it was discovered on 31 October.
...
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fichef-1.bbci.co.uk%2Fnews%2F624%2Fcpsprodpb%2F1330%2Fproduction%2F_93621940_crack.jpg&hash=18a8e78eb457c0b105d9e09cfbc8452d)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Sigmetnow on January 17, 2017, 12:55:40 AM
"We've spent a long time finding the new site for Halley VI and of itself this site isn't directly at risk - it's just the unpredictability of the whole area."
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: peterlvmeng on January 17, 2017, 02:31:49 AM
I do not know what does it mean. But I think we can probably forsee three period climate change.
1. Sea ice changing
1.1 Arctic sea ice becomes seasonal sea ice (<5yr)
1.2 Albedo-warming and ocean current redistribution makes the sea ice cannot form extensively even in winter (just along the continent)(<10yr)
2. ice shelf and ice sheet in Greenland and Antarctic. We are on the tipping point of sea ice so we do not have seen the continent ice melt out of control(just unexpected).(<?yr)
3. The unexpected huge climate change spreads over every corner of the world.(<?yr)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Gray-Wolf on January 17, 2017, 11:26:21 AM
With Larsen C and now our BAS base the Uk has never seen as much Antarctic coverage on their news!
Both sites look out over Weddell. Are we expecting sea ice buttressing from Weddell to lessen over the coming years and so see more 'active' shelfs around the area?

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: bairgon on January 17, 2017, 03:05:42 PM
Is the new crack visible on satellite images? I had a quick look but don't know the best resources to use.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Tealight on January 17, 2017, 05:33:00 PM
Is the new crack visible on satellite images? I had a quick look but don't know the best resources to use.

I've only seen the new crack on Sentinel 2A images (10m resolution). Sentinel 1 just doesn't have enough resolution and clarity. The crack is at most 40m wide and over 40km long so I can't show it over its full length, it would be an over 4000 pixel wide image. The last cloud free image is from the 30th December, maybe the crack has grown since then.

Click on images for full resolution.

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on January 17, 2017, 06:27:11 PM
Here is a screen shot of the area from Sentinel 1.  I like how you can see the tracks leaving from the old station location, can't see the new location though.  Looks to me that you can see the crack forming in the upper right area.

http://www.polarview.aq/antarctic (http://www.polarview.aq/antarctic)

http://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SSH_20170112T000231_A69D_S_1.final.jpg (http://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SSH_20170112T000231_A69D_S_1.final.jpg)  (62 MB file)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: DrTskoul on January 18, 2017, 12:08:10 PM
Drone view of Halloween crack...

http://www.bbc.com/news/video_and_audio/headlines/38658836 (http://www.bbc.com/news/video_and_audio/headlines/38658836)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 28, 2017, 06:29:00 PM
The British Antarctic Survey press release regarding the enforced relocation to Halley VIa can be found here...

https://www.bas.ac.uk/media-post/halley-research-station-antarctica-to-close-for-winter/ (https://www.bas.ac.uk/media-post/halley-research-station-antarctica-to-close-for-winter/)


@ Tealight

I know you were working on trying to quantify the albedo effect for the SIPN, but are you also doing anything similar for the seas around Antarctica? One of the factors that concerns me regarding the current behaviour of Antarctic sea ice is that, at perihelion, Earth is about 5 million kms closer to the sun than at aphelion. Consequently, measured at TOA on perihelion, insolation is a bit over 6% greater than at aphelion.

The date of perihelion currently occurs somewhere in the range 2nd to the 5th of January, with aphelion currently happening between the 3rd and 6th of July. As these windows are only about 2 weeks after the relevant solstice, this surely has an appreciable effect on the energy going into the Southern Ocean?

If Antarctic sea ice is finally starting to show the same shrinkage pattern as its boreal cousin, rather than this just being another wild fluctuation, this would represent yet another unwelcome energy imbalance.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: oren on January 28, 2017, 06:37:40 PM
@Bill
Tealight's Antarctic work (FDD anomaly chart) is supposed to be found here
https://sites.google.com/site/cryospherecomputing/warming-potential/antarctic-graphs (https://sites.google.com/site/cryospherecomputing/warming-potential/antarctic-graphs)
Although for some reason the images don't load for me at the moment.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 28, 2017, 07:03:50 PM
...Are we expecting sea ice buttressing from Weddell to lessen over the coming years and so see more 'active' shelfs around the area?

Looking at these NSIDC concentration charts for the Antarctic (dated 27 Jan 2017 and 27 Jan 2014), I think it's safe to say that the buttressing effect of sea ice ain't what it used to be...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 28, 2017, 07:11:22 PM
@Bill
Tealight's Antarctic work (FDD anomaly chart) is supposed to be found here
https://sites.google.com/site/cryospherecomputing/warming-potential/antarctic-graphs (https://sites.google.com/site/cryospherecomputing/warming-potential/antarctic-graphs)
Although for some reason the images don't load for me at the moment.

Oren - I'm a complete eedjit!!!!

I'm aware of that site, but somehow failed to register that it addressed the Antarctic, as well as the Arctic - quelle plonker!


@ Tealight: Sorry for being so dumb, it comes as a result of too many birthdays.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: DrTskoul on January 28, 2017, 08:33:56 PM
@Bill
Tealight's Antarctic work (FDD anomaly chart) is supposed to be found here
https://sites.google.com/site/cryospherecomputing/warming-potential/antarctic-graphs (https://sites.google.com/site/cryospherecomputing/warming-potential/antarctic-graphs)
Although for some reason the images don't load for me at the moment.

Oren - I'm a complete eedjit!!!!

I'm aware of that site, but somehow failed to register that it addressed the Antarctic, as well as the Arctic - quelle plonker!


@ Tealight: Sorry for being so dumb, it comes as a result of too many birthdays.

Being able to self reflect means you have room for many more...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: crandles on January 28, 2017, 08:38:14 PM
...Are we expecting sea ice buttressing from Weddell to lessen over the coming years and so see more 'active' shelfs around the area?

Looking at these NSIDC concentration charts for the Antarctic (dated 27 Jan 2017 and 27 Jan 2014), I think it's safe to say that the buttressing effect of sea ice ain't what it used to be...

Ice shelves (up to a few hundred metres thick) do have buttressing effects but sea ice that is what 1- 3m thick, and often quite mobile, buttressing effect? Surely it is too thin and mobile to hold back glaciers? Landfast sea ice may be less mobile, but if 'sea ice' means it is all formed from sea water rather than some of the ice being allowed to be from land, does it get thick enough? sounds rather dubious to me but I am no expert.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: oren on January 28, 2017, 10:18:42 PM
Ice shelves (up to a few hundred metres thick) do have buttressing effects but sea ice that is what 1- 3m thick, and often quite mobile, buttressing effect? Surely it is too thin and mobile to hold back glaciers? Landfast sea ice may be less mobile, but if 'sea ice' means it is all formed from sea water rather than some of the ice being allowed to be from land, does it get thick enough? sounds rather dubious to me but I am no expert.
I imagine (not based on actual knowledge unfortunately) that sea ice might have a protective effect by inhibiting wave action next to the ice shelf/glacier, by limiting warming of the nearby sea's top layer, and by keeping calved bergs nearby.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Tor Bejnar on January 29, 2017, 12:10:37 AM
I recall a discussion a year or 3 ago in relation to Petermann Glacier concerning sea ice inhibiting or not inhibiting the glacier's advance.  I recall some published author's blog indicating sea ice may provide some buttressing.  Land-fast (glacier-fast?) sea ice obviously prevents wave action or warm surface water cutting into the ice, but it apparently doesn't prevent warm salty water at the base melting the bottom of the glacier's toe.

But glacial retreat and advance are not independent or totally opposite concepts.  Retreat happens when melting at the glacial front is faster than its advancing, and advancing is related to the speed of the glacier (faster in the middle than the sides, and faster where the longitudinal surface of the glacier is steeper), generally faster after/during warm spells (summer and day) and slower after/during cold spells (winter and night), associated, at least partially, with lubrication.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 29, 2017, 01:47:10 AM
Ice shelves (up to a few hundred metres thick) do have buttressing effects but sea ice that is what 1- 3m thick, and often quite mobile, buttressing effect? Surely it is too thin and mobile to hold back glaciers? Landfast sea ice may be less mobile, but if 'sea ice' means it is all formed from sea water rather than some of the ice being allowed to be from land, does it get thick enough? sounds rather dubious to me but I am no expert.
I think the confusion here lies in the interpretation of the word "buttressing". It is probably quite common to think in terms of the flying buttresses used to great effect since the 12th Century. These were typically designed to provide an inward force on church walls which would counteract the outward pushing effect of the roof mass. As such, these buttresses were, by necessity, pretty substantial lumps of masonry.

Although sea ice does present something of a barrier to the egress of the ice in a glacier by means of mechanical inertia, that is probably only a second order effect. What sea ice really does is to help reduce basal erosion at the calving front of the glacier (or indeed, of an ice shelf).

See, for example, this NASA article...
http://earthobservatory.nasa.gov/Features/SeaIce/ (http://earthobservatory.nasa.gov/Features/SeaIce/)

The salient part is just below the photo of a polar bear on some sea ice, wherein the article states that...
"The sea ice layer also restricts wind and wave action near coastlines, lessening coastal erosion and protecting ice shelves."

Buttressing effects of a more mechanical nature are discussed here...
https://nsidc.org/cryosphere/sotc/ice_sheets.html (https://nsidc.org/cryosphere/sotc/ice_sheets.html)

I recall a discussion a year or 3 ago in relation to Petermann Glacier concerning sea ice inhibiting or not inhibiting the glacier's advance.  ...
Possibly the scientist to which Tor refers was Jason Box. Please see...
https://nsidc.org/cryosphere/icelights/2011/09/greenland%E2%80%99s-glaciers-and-arctic-climate (https://nsidc.org/cryosphere/icelights/2011/09/greenland%E2%80%99s-glaciers-and-arctic-climate)

In that article, Jason states that...
"... The decline in sea ice could speed up ice loss in Greenland. “It is reasonable to speculate that changes in sea ice duration and concentration in the vicinity of glacier fronts should impact their stability,” said Box. “As the sea ice melts, the ocean can be stirred up more by strong Arctic winds and change fjord water circulation and the sub-marine melt regime.”  Winter sea ice also acts as a buttress against glacier ice flow, seasonally slowing the flow speed. An earlier break-up and later freeze-up of sea ice in the fjords may play a role in the ice sheets' mass balance ..."
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Tor Bejnar on January 29, 2017, 03:47:06 AM
Jason Box: I'm sure this is the reference to whom I referred. 
E-gads, it could have been a discussion from 5 years ago!
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: crandles on January 29, 2017, 01:20:38 PM
Thanks for the information. Yes protecting against waves and wind stirring up water and therefore against undercutting of ice shelves/glaciers does make sense. Sorry for the misinformation distraction.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 29, 2017, 05:23:41 PM
Jason Box: I'm sure this is the reference to whom I referred. 
E-gads, it could have been a discussion from 5 years ago!
It could have been more recent. I remember being involved in precisely this type of debate somewhere on the forum, and I'm pretty sure that Petermann was mentioned. I thought that this had happened during 2016, but my recollection of when anything happened is somewhat unreliable. [Gross Understatement]

Thanks for the information...
de rien
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: oren on January 30, 2017, 12:47:36 AM
Jason Box: I'm sure this is the reference to whom I referred. 
E-gads, it could have been a discussion from 5 years ago!
It could have been more recent. I remember being involved in precisely this type of debate somewhere on the forum, and I'm pretty sure that Petermann was mentioned. I thought that this had happened during 2016, but my recollection of when anything happened is somewhat unreliable. [Gross Understatement]

Thanks for the information...
de rien
I may have been to blame. You are probably referring to Zachariae Isstrom, where the sea ice seems to slow down calvings. At least in Augusts when it does clear the ZI retreats significantly. My personal belief is that the sea ice holds the calved icebergs in the almost-closed inner bay, and the whole mass serves to slow down marginal calvings, which tend to happen when the buttressing is suddenly washed away. Search the ZI thread for such discussions. I think Aug 2014 was such an example.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on January 30, 2017, 10:08:15 AM
For those of you interested there's more information on the stability of the ice shelf and the positioning of Halley station in the following articles.

http://nora.nerc.ac.uk/15413/ (http://nora.nerc.ac.uk/15413/)
Proposed construction and operation of Halley VI Research Station and demolition and removal of Halley V Research Station, Brunt Ice Shelf, Antarctica. Final Comprehensive Environmental Evaluation

https://www.bas.ac.uk/data/our-data/publication/numerical-simulations-of-the-ice-flow-dynamics-of-the-brunt/ (https://www.bas.ac.uk/data/our-data/publication/numerical-simulations-of-the-ice-flow-dynamics-of-the-brunt/)

http://onlinelibrary.wiley.com/doi/10.1029/2008JF001124/full#jgrf568-bib-0003 (http://onlinelibrary.wiley.com/doi/10.1029/2008JF001124/full#jgrf568-bib-0003)
Roles of marine ice, rheology, and fracture in the flow and stability of the Brunt/Stancomb-Wills Ice Shelf

Worryingly it seems even with the numerical models and the ability to monitor the different ice sheet movements the BAS is still unable to determine if their station is safe...
 
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: charles_oil on January 30, 2017, 11:11:23 AM
I've just started reading the fascinating book on the Trans-Antarctic expedition in 1955-8 by Fuchs and Hillary - The Crossing of Antarctica.

There are great descriptions of the ice forming, conditions and sea state. It would be amazing to link their comments into the actual locations - and compare with current / recent conditions.

In the first two years they initially arrived and set up the Shackleton base in the Weddel sea, at the base of Flichner along the coast from the Halley bay base.  They found that the best way to progress with the ships making the supply run (Dec/Jan) was to use the extensive "landwater" lead that they found along the coast - their name for it.   

There was a section of ice at the shore before the start of the ice shelf proper.  Some stores which were waiting to get to the base and were held here during early 1956 were lost when a section broke away in late March.

The landwater lead would mean that in effect there was no physical buttressing by the sea ice, but clearly the effect of the sea ice was to have a calmer water area - which they often used for their seaplane to take off.

The book is very well illustrated with some great photos.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: charles_oil on January 30, 2017, 11:34:16 AM
... and some amazing footage of the ice in this film.   Note sea ice in the first 2 minutes, and again at about 12 minutes in vol 1.  It does show a lot of swell at times though, so the landwater lead wasn't always calm.

https://www.nzonscreen.com/title/antarctic-crossing-1958 (https://www.nzonscreen.com/title/antarctic-crossing-1958)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 30, 2017, 09:27:16 PM
Jason Box: I'm sure this is the reference to whom I referred. 
E-gads, it could have been a discussion from 5 years ago!
It could have been more recent. I remember being involved in precisely this type of debate somewhere on the forum, and I'm pretty sure that Petermann was mentioned. I thought that this had happened during 2016...
I may have been to blame. You are probably referring to Zachariae Isstrom, where the sea ice seems to slow down calvings...

Tor & Oren,
I used the SEARCH feature provided on the ASIF, with the search string set to "Petermann" and the User identity set as me. The ensuing search showed that there was a brief flurry of comments about this subject (involving, amongst others, the 3 of us) on Espen's IJIS thread. It starts on page 53 at around #2635 on June 30th, 2016.

As the buttressing effect of sea ice was/is more than a little OT for the IJIS thread, I think we were all a bit reluctant to go into too much detail.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: oren on January 30, 2017, 11:27:28 PM
Tor & Oren,
I used the SEARCH feature provided on the ASIF, with the search string set to "Petermann" and the User identity set as me. The ensuing search showed that there was a brief flurry of comments about this subject (involving, amongst others, the 3 of us) on Espen's IJIS thread. It starts on page 53 at around #2635 on June 30th, 2016.

As the buttressing effect of sea ice was/is more than a little OT for the IJIS thread, I think we were all a bit reluctant to go into too much detail.
Thanks for looking that up Bill. My memory was somewhat muddy.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on January 31, 2017, 12:54:11 AM
@ Tor

Thanks for the quick email outlining the comment link technique. Hopefully I can remember it for more than just a couple of minutes.

If I've followed your instructions correctly, the link below should take you to the relevant passage - although you might perhaps want to start one or two comments further up. The relevant bits extend to the bottom of that page.

Thanks again for the quick tutorial. :)

...However, there is a mechanism whereby the loss of sea ice will cause an acceleration in SLR...

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Bill Fothergill on February 02, 2017, 11:55:24 PM
It seems like the relocation to Halley VIa has been completed.

https://www.bas.ac.uk/media-post/halley-vi-research-station-relocation-success/ (https://www.bas.ac.uk/media-post/halley-vi-research-station-relocation-success/)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: bairgon on February 03, 2017, 06:59:35 AM
Video of the move at

http://www.bbc.co.uk/news/science-environment-38849078 (http://www.bbc.co.uk/news/science-environment-38849078)

Amusing error in the commentary: it already is icy - it would be a "watery fate at the bottom of the ocean".
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: maga on February 04, 2017, 03:33:00 PM
Does anyone understand the new crack? I don't! The old one ("chasm") looks reasonable and will one day calve the complete western corner but the new crack starts in the middle of the ice shelf and bends from almost parallel to the flow direction to a more perpendicular direction. It doesn't appear to be directly caused by the faster flowing Riiser ice tongue since it is on the wrong side of the shelf. It also appears to trend to the wrong side of the ice rumples. Not sure if it will lead to a calving event anytime soon but it doesn't look good for the Brunt ice shelf. If the front goes, the rest will probably follow soon since it looks that cracks originating near the grounding line heal over time and stabilize the shelf.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: charles_oil on June 13, 2017, 12:31:20 PM
Did anyone catch the Horizon programme on moving the Halley base ? - It was on late last night on BBC2.  Sadly I only managed to catch 4 minutes of it & it looked interesting .....
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Anne on June 13, 2017, 01:00:17 PM
Did anyone catch the Horizon programme on moving the Halley base ? - It was on late last night on BBC2.  Sadly I only managed to catch 4 minutes of it & it looked interesting .....
It's still available here (with 29 days left to watch): http://www.bbc.co.uk/programmes/b08tj2zr (http://www.bbc.co.uk/programmes/b08tj2zr)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: charles_oil on June 13, 2017, 02:56:33 PM

sadly not from outside the UK  :(

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: John_The_Elder on June 13, 2017, 04:13:31 PM
Chrome browser with:
 https://chrome.google.com/webstore/detail/beebs-access-bbc-iplayer/opmliiafmgjkgkfadkpomlefdllhajdi?utm_source=chrome-app-launcher-info-dialog

will allow you to view BBC

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 31, 2017, 04:27:52 PM
Update:  Base will be operational over the summer,  but be shutdown again for the winter.
https://www.bas.ac.uk/media-post/115024/
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on January 11, 2018, 11:07:49 PM
Here is a screen shot of the area from Sentinel 1.  I like how you can see the tracks leaving from the old station location, can't see the new location though. 
One year on, and the new crack is quite visible on Sentinel 1.  Shot from
http://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20180110T233040_9679_S_1.final.jpg (47 mB) 
Looks like you can see the new base location as well.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FredBear on January 12, 2018, 02:19:02 PM
In the top left of the full image from reply 37 by solartim27 there is the end of an iceberg (opposite the spike on the coastline). This 'berg spent last summer spinning westward round Antarctica, over-wintering in the sea-ice just northeast of its present location. In arctic.io/explorer (Antarctic) it breaks free 2017-10-04, gets round the bend by 2017-11-04 and has spent the time since drifting round in circles. I had thought it might continue down towards the Brunt ice-shelf, possibly disrupting things there as it seems to hug the coastline, but it has not travelled far this season!
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: maga on January 13, 2018, 08:19:32 PM
Yes. This seems to be the normal behavior. Wait until mid February or March, then the iceberg will start to move again. Usually rather fast at first until the sea ice becomes thick enough to slow things down.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: maga on January 13, 2018, 08:31:47 PM
I'm still wondering how things will unfold at Brunt. Currently my best guess is that the chasm will connect to the Halloween crack somewhere behind the Mc Donald ice rise. Still 10 km to go though. The Halloween crack still seems to terminate on the wrong side of the ice rise and I guess a second parallel crack will form just next to it close to the ice rise to eventually relase the big ice berg. The result could be a complete disintegration of the Brunt ice shelf because the ice closer to the coast seems to be much weaker and the connection to the Mc Donald ice rise would be narrow and unstable (in case the chasm terminates downstream of the ice rise). I even wonder whether the Stancom-Wills ice tongue could react to this and start to bend over because of the pressure of the ocean current. In an extreme scenario it may even break off. Any other ideas?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on October 12, 2018, 01:57:44 PM
Some new imagery of the Brunt Ice shelf
looks like the cracking in this area will be something to watch.

https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.59450674962629&lng=-26.0650634765625&zoom=9&preset=1_NATURAL_COL0R&layers=B01,B02,B03&maxcc=100&gain=0.4&gamma=1.0&time=2015-01-01%7C2018-10-12&atmFilter=&showDates=true&showImage (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.59450674962629&lng=-26.0650634765625&zoom=9&preset=1_NATURAL_COL0R&layers=B01,B02,B03&maxcc=100&gain=0.4&gamma=1.0&time=2015-01-01%7C2018-10-12&atmFilter=&showDates=true&showImage)

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on October 12, 2018, 03:12:48 PM
So a link to the BAS site on the issue.

https://www.bas.ac.uk/project/brunt-ice-shelf-movement/#about

and a paper on the changes
https://www.the-cryosphere.net/12/505/2018/tc-12-505-2018.pdf

with an animation comparing last October, this Feb and now.

Needs a click to animate - Halley is in the bottom right of the image
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on October 12, 2018, 07:31:37 PM
With missing fixed points like mountain ranges it is hard to say whether the upper (northern?) part is moving away from the lower (southern?) part or vice versa. Does anyone know?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 13, 2018, 02:38:10 AM
More interesting is the crack extending up from the bottom center.  The original site was on the other side of that.  Could be a very large berg relatively soon.  This year,  next year?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on October 13, 2018, 11:58:59 AM
Stephan,
The top left corner of the animation has the MacDonald Ice rumples which are fixed
everything else is kind of moving around them.

I've annotated an overview below with the end of chasm 1 in green (near as I can tell) and the general ice movement in Red with Halley inset.

If you review the animation and look for a particular feature / dog leg in the halloween crack you will see how the general movement is affecting the shelf.

Solartim27,
I tend to agree, just eyeballing it I think the end of the cracks are just 9km apart.

The crack appears to have grown around 5km since the end of Feb which is significantly different from the 1.36km per year as has been observed over the last few seasons.

The overall issue seems to be more to do with shelf stability - if Chasm 1 completes the calving downstream of the MIR then the shelf is still stable if lacking a good chunk of area.  If, as is suggested by the strain model in Figure 7 from the paper in my last post (extract below), chasm 1 meets up with the halloween crack then the shelf is no longer pinned and could rapidly destabilize. 
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 13, 2018, 04:10:13 PM
I forget if I posted this site earlier, but it gives an excellent overview of the area.  The inset of the picture only has the crack advancing through Dec 2017.
https://www.bas.ac.uk/project/brunt-ice-shelf-movement/
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 15, 2018, 05:09:41 AM
Here's an image from the latest Polarview, looks to me like the Chasm is progressing both North and West.  Hard to say which direction will win.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 19, 2018, 12:38:44 AM
Here is a world view gif showing the progression from 2010, 2016, 2017, and 2018
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 21, 2018, 05:28:53 PM
Looks to me like Chasm 1 has made a connection to the coast, though I suppose that doesn't mean it will go anywhere right away.  Anyone have a Sentinel or Lands at image?  Snip from Polar view, original is 15 mb
https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SDH_20181020T232244_E858_S_1.final.jpg
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 29, 2018, 03:44:56 AM
Here's a snip from the latest Polarview.  Looks like Chasm 1 has joined up with the Halloween crack, but hard to say for certain.  I find the straightness of the new crack section to be a concern, perhaps a data glitch in that area? Of course we just saw the rectangular bergs.  Even if it is all the way through, it still may not move significantly.  It also looks to me like there is also a crack extension heading to the coast, but perhaps I need to clean my glasses.
Original image 34 mb
https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SDH_20181027T231436_AC7B_S_1.final.jpg
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 30, 2018, 06:25:12 AM
Okay, so that's two in a row, but it still looks weird.  Original 10 mb
https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20181029T234745_234F_S_1.final.jpg
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on October 30, 2018, 05:29:29 PM
Not quite there yet. 30 Oct image, 55 mb
https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20181030T034958_81D5_S_1.final.jpg
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on October 30, 2018, 06:03:18 PM
Here's a view switching between the 7th and the 27th Oct - you can clearly see the crack has extended and checking here https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.53564672956175&lng=-26.096477508544922&zoom=13&preset=1_NATURAL_COL0R&layers=B01,B02,B03&maxcc=85&gain=0.4&gamma=1.0&time=2015-01-01%7C2018-10-27&atmFilter=&showDates=true (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.53564672956175&lng=-26.096477508544922&zoom=13&preset=1_NATURAL_COL0R&layers=B01,B02,B03&maxcc=85&gain=0.4&gamma=1.0&time=2015-01-01%7C2018-10-27&atmFilter=&showDates=true)
at the crack tip shows this to be about 1 km over the 20 days.

i think we could be looking at a differently shaped ice shelf before xmas...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on November 05, 2018, 06:57:14 PM
Very nice animation from July 30, 2016 to Oct 30 2018

https://adrianluckman.wordpress.com/2018/10/31/
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FrostKing70 on November 05, 2018, 07:43:29 PM
Interesting animations!   Does any one have access to information on how big (area and volume) the calving events would be from Chasm 1 and the Halloween Crack (when they eventually go, although I believe one or both will happen this summer)?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FrostKing70 on November 06, 2018, 08:27:35 PM
I have done some poking around on the internet and have not been able to find any indication of the potential size of the calving events.   Can any one point me towards to good source?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on November 07, 2018, 07:45:35 AM
Here is a wider view of the Brunt Ice Shelf showing the other side of the Halloween Crack.  Looks like there is a chance for a significant  calving there.
Original image 53 mb https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20181106T233049_C2BC_S_1.final.jpg

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on November 20, 2018, 03:46:54 PM
SolarTim27,

I think you are right, here's this month's animation showing the MIR area.
you can see that in the area above the widening Halloween crack there is another crack starting up across the area of the shelf that you have highlighted.

No sign of Crevasse 1 at this scale yet but my guess is that it won't be long.

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FredBear on November 24, 2018, 10:39:09 PM
Just seen this drone footage of the crack:-

https://www.weatherbug.com/weather-videos/wow/20181117-Crack-In-The-Brunt-Ice-Shelf
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FredBear on December 12, 2018, 06:34:56 PM
  .   .   and Halley opened up again by BAS   .    . 

https://www.bas.ac.uk/media-post/summer-fieldwork-begins-at-halley
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on December 13, 2018, 05:35:37 PM
Looks like Chasm 1 has advanced some more - very close to calving now...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FredBear on December 21, 2018, 02:58:21 PM
Just found this on the British Antarctic Survey site:-

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: SteveMDFP on December 26, 2018, 08:17:04 PM
Turns out, the Halley crew doesn't just spend all their time dodging new cracks in the ice shelf.
They also monitor electronic signals related to space weather.
Some of these are low-frequency radio waves, corresponding to audio wavelengths.
So, they can just hook up the electronic signals directly into an audio recorder.
So, for your aural pleasure,

Listen to the Creepy Noises Picked Up at a Space Weather Station in Antarctica
https://gizmodo.com/listen-to-the-creepy-noises-picked-up-at-a-space-weathe-1831234519 (https://gizmodo.com/listen-to-the-creepy-noises-picked-up-at-a-space-weathe-1831234519)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on December 31, 2018, 03:55:45 AM
Looks to me like there is significant crack development right to the left of the Longitude line.  That doesn't mean that if it does go all the way that the berg will move anywhere, or any time soon, but I feel there is a non-zero chance that Brunt could break apart this summer.
Snip from https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20181230T233130_2AC8_S_1.final.jpg   (31 MB)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on December 31, 2018, 04:04:15 AM
Here's a worldview GIF from the end of November to the end of December. Hard to say if the crack really expanded that much, or if it's just surface snow melting, blowing, or something to make it more visible.  A nice Sentinel shot would be nice around now.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on December 31, 2018, 05:24:21 PM
There was an almost clear Sentinel shot of Brunt on the 29th.  Here's a gif from September until then from the playground in natural color, and a 2nd shot in the same area with the NDWI band selected. ( Note the 3 km scale bar in the lower right corner )
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on January 11, 2019, 02:42:16 PM
Well, there was a clear image on the 8th Jan so here's the new year's animation.

Not a lot of changes -
expansion of the crack above the halloween crack radiating from the MIR
Movement around the MIR

There's been a suggestion on the SAR images of chasm 1 forking towards the tip, not really seeing anything in the visual images though.

I do like the NDWI band as a way to highlight the cracks.
 
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on January 18, 2019, 07:38:07 PM
World view is nice and clear today, hopefully we can get a visual shot this weekend.  Looks like the cracks might have joined up right upstream of the ice rise.
https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20190118T002007_76A0_S_1.final.jpg  (32 MB)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on January 18, 2019, 07:51:44 PM
Worldview shows lots of development over the last four weeks, but the resolution is not high enough to see for certain.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on January 19, 2019, 01:52:25 AM
Sentinel came through today, gif from 29 Nov to 18 Jan, NDWI band.  Not quite there yet.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on January 21, 2019, 05:26:34 PM
 :o

getting very close now - maybe 5km between the cracks at this stage.

and an interesting article published in October - read it now before it becomes outdated news.
https://www.the-cryosphere.net/12/3361/2018/tc-12-3361-2018.pdf
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on January 31, 2019, 09:58:46 PM
Next full moon? Excellent gif at
https://mobile.twitter.com/bert_polar/status/1090755654824984579
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on February 10, 2019, 10:33:09 PM
I just visited Sentinel images of the Brunt Ice Shelf. The Chasm 1 crack has lengthened about 2 km between Dec 29, 2018 and Feb 07, 2019. Its distance to the tip of the Halloween Crak is now only around 8 km. I wonder when these two cracks will meet and what happens thereafter...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on February 11, 2019, 01:51:21 PM
Indeed, taking a look at the recent polarview IW image it's getting very close now.

It looks like chasm 1 will not meet the Halloween crack but just end with the calved section below the MIR on the image below.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: interstitial on February 13, 2019, 02:29:16 AM
I found this image of the brunt ice shelf looking at the new thread of Antarctic expeditions.
https://www.bas.ac.uk/project/moving-halley/

It looks like some of what I thought was new growth is harder to see on some days.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Andreas T on February 14, 2019, 07:47:19 PM
This paper looks interesting and has not been linked to before it seems:
https://www.the-cryosphere-discuss.net/tc-2018-206/tc-2018-206.pdf (https://www.the-cryosphere-discuss.net/tc-2018-206/tc-2018-206.pdf)
one small quote:
Quote
However, the DEM surface topography (and ICESat data) shows large variations in the distribution of
the incorporated icebergs (Fig. 5), and the ice shelf draft upstream of the MIR (Fig. 6) which can be used to
determine if grounding will be maintained. For example, there are currently portions of the ice shelf, due to pass
over MIR 4-12 years from 2017 that may have insufficient draft to ground, with no keels extending below -200
m. At this time the ice shelf might be more prone to reduced, or loss of, contact (Fig. 6b).
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: solartim27 on February 20, 2019, 04:28:54 PM
Latest Polarview shot. Have some clear skies on Worldview, so hopefully there's a Sentinel nearby.  31 MB link  https://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20190219T235547_542C_S_1.final.jpg
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on February 20, 2019, 05:49:01 PM
It's been noticed by Nasa and there's a post on the earth observatory today

https://earthobservatory.nasa.gov/images/144563/countdown-to-calving-at-brunt-ice-shelf

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on February 20, 2019, 10:09:58 PM
Thank you for that link.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: FredBear on February 28, 2019, 09:20:16 PM
And another winter evacuation for 2019:-
https://www.bbc.co.uk/news/science-environment-47408249
https://www.bas.ac.uk/media-post/halley-research-station-closes-for-2019-antarctic-winter
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Jim Hunt on February 28, 2019, 09:52:00 PM
Thank you for those links Fred!
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on March 01, 2019, 06:45:07 PM
On Feb 27 a new clear Sentinel picture was available. It shows that the crack "Chasm1" has grown into NNW direction by about 2 km (compared to Jan 24). So the distance to the western end of the Halloween crack has reduced to about 7 km, the distance to the 2nd crack west of McDonnell Ice Rise is about 6,5 km.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: interstitial on March 02, 2019, 05:33:40 AM
Brunt Ice shelf Feb 27th @ 3:49 am UTC
The crack is hard to see but shows up better in the original 53mb file. 

The scale bar is approximate but should be close enough. I don't have the exact pixel resolution for the image so I used the latitude lines on the picture. I couldn't find the exact distance between the 75th and 76th southern latitude. I did find the distance is 110.567 at the equator and 111.699 at the poles so interpolated and came up with 111.5209 km between the 75th and 76th parallel. I measured the number of pixels using imageJ and used that to scale the image.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on March 06, 2019, 03:54:01 PM
In a reminder to sit back and take a look at the bigger picture a fairly large iceberg approaches the Brunt Ice shelf caught in the currents around the coast.

So the final event may not be determined by the gradual progression of the crack but by the shock of an external impact...

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on March 06, 2019, 04:33:29 PM
That would be fascinating actually...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on March 07, 2019, 04:09:51 PM
Looks like the crack is complete.

Link >> http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201903/S1B_IW_GRDH_1SSH_20190306T233046_8D4C_S_1.8bit.jp2
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on March 07, 2019, 04:23:22 PM

So do you guys think the iceberg hit the shelf?

It looks like some pieces chipped off of the iceberg (marked).
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: crandles on March 07, 2019, 04:38:19 PM
Looks like crack might be complete at resolution shown.

Zooming in a little more, I am not even sure of the cracks marked with lines drawn above and or right of feature. Is interpreting more cracks justified?
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: iwantatr8 on March 08, 2019, 03:28:12 PM
Well looking at the latest images it looks very much like the shelf has calved to me.

And fortunately below the MIR so this should help ensure the shelf stays stable.

as to if the Iceberg hit, it's possible but I guess we may never know.

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on March 18, 2019, 08:34:16 AM
Yesterday we finally got a new clear Sentinel 2 shot.

Crandles got it right, the crack has not completed yet.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Susan Anderson on March 29, 2019, 06:36:44 PM
Reporting in the New York Times 28 March:
An Iceberg Twice the Size of New York City Is About to Split From Antarctica: Two rifts on the Brunt Ice Shelf in Antarctica are close to creating an iceberg over 560 square miles in size. Scientists say the calving event could happen any day now.
https://www.nytimes.com/interactive/2019/03/28/climate/antarctica-brunt-iceberg.html (https://www.nytimes.com/interactive/2019/03/28/climate/antarctica-brunt-iceberg.html)

brief but good graphical presentation ...

I think A68 calved in winter. Is it a thing, that as it gets colder the calving potential continues? If so, for how long? Might be, answer is, nobody really knows, just sayin' ... [ocean temps lag a lot, for example in Boston it's just beginning to warm up a tiny bit, over 3 months later]
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on March 29, 2019, 06:41:31 PM
Wow, what a great visualisation (even though this is weirdly projected)! This is how you do it!

Thanks for the link, Susan.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on March 31, 2019, 09:02:33 PM
Chasm1 has made it's way to McDonald ice rumples (now for real (i think)).

Link >> https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20190330T233046_A43B_S_1.final.jpg

Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: crandles on April 05, 2019, 03:21:53 AM
https://www.bbc.co.uk/news/science-environment-47817510

Quote
Antarctic: No role for climate in Halley iceberg splitting

Jan De Rydt and Hilmar Gudmundsson have built a model to describe the behaviour of the floating ice platform, which is known as the Brunt Ice Shelf.
he Brunt is essentially an amalgam of glacier ice that's flowed off land and pushed out to sea at a rate of about 400m per year.

Incorporating satellite and surface-gathered data, the team's model reveals how stress is distributed across the 150-250m-thick structure. And it predicts accurately where cracks are likely to develop and the path they will take.

"It all fits together; it's a very compelling piece of work," says Prof Gudmundsson.

"It shows that the chasm started to grow because of the stresses building up, and they built up because of the natural growth of the ice shelf. The ice shelf itself created this chasm."

...

"The chasm's been growing at about 1-2km a year and we haven't really seen any slow-down in winter. It's almost through already, but I would say it should happen within a year."
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Susan Anderson on April 06, 2019, 09:45:56 AM
@crandles

Useful and fascinating, makes sense.

Trouble is, headlines are all too often oversimplifications. I get it, but in fact global warming and climate will play a part in ice breakoffs as time goes on. Perhaps more after the break (the stress explanation makes sense) in terms of where the ice ends up, and how much the surrounding area will be degraded (if it is).
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on April 12, 2019, 06:14:12 PM
In the same sense as BBC (posting above) Wetteronline in Germany presented a short information about the expected calving of parts of the Brunt Ice Shelf:
https://www.wetteronline.de/klimawandel/antarktis-schelfeis-hat-risse-riesen-eisberg-droht-abzubrechen-2019-04-12-aa
The main claim is that this is a natural process as this part of Antarctica has not seen a relevant warming in the past decades (but only air temperature mentioned; no information about increasing sea temperatures)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Steven on June 14, 2019, 08:01:47 PM
From Adrian Luckman:  animation of the McDonald Ice Rumples on Brunt Ice Shelf

https://adrianluckman.wordpress.com/2019/06/14/mcdonald-ice-rumples-on-brunt-ice-shelf/

(https://i.imgur.com/nNeBn7H.gif)
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on June 14, 2019, 09:11:51 PM
Thanks for that wonderful animation.
Neither the Halloween crack has made it to or aside the McDonald ice rumple nor has Chasm 1 connected to one of the cracks west of that ice rumple. A bigger calving seems not very likely for the moment.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on June 15, 2019, 07:02:57 AM
nor has Chasm 1 connected to one of the cracks west of that ice rumple.

Sorry, Stephan, i have to correct you.

Chasm1 has cracked all the way to the rumple now.

I'm expecting calving any time now.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: Stephan on June 15, 2019, 11:35:42 AM
OK. I could not detect this tiny crack in the animation above.
Nevertheless I wonder about the stability of all the ice with a lot of thick cracks W and N of that ice rumple. In my lay man opinion it should have calved already...
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on June 15, 2019, 12:15:42 PM
For how i understand it, to become loose, it also needs to melt from the bottom.
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: interstitial on June 15, 2019, 11:57:39 PM
That makes more sense. I saw several cracks that I thought should let it break free but the just seemed to get snowed over and disappear. Thanks BL
Title: Re: Halley base shut down and new crack in Brunt shelf
Post by: b_lumenkraft on June 16, 2019, 05:35:16 AM
Welcome, Interstitial. :)