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Author Topic: Halley base shut down and new crack in Brunt shelf  (Read 6873 times)

charles_oil

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Halley base shut down and new crack in Brunt shelf
« 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

Lets hope it can get fixed !

FredBear

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #1 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?
« Last Edit: January 16, 2017, 11:53:23 PM by FredBear »

Tor Bejnar

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #2 on: January 17, 2017, 12:17:05 AM »
from the BBC article:

http://www.bbc.co.uk/news/science-environment-38643420
[/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.
...

Arctic ice is healthy for children and other living things.

Sigmetnow

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #3 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."
People who say it cannot be done should not interrupt those who are doing it.

peterlvmeng

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #4 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)

Gray-Wolf

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #5 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?

KOYAANISQATSI

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bairgon

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #6 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.

Tealight

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #7 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.


solartim27

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #8 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/images/105_S1jpgfull/S1B_EW_GRDM_1SSH_20170112T000231_A69D_S_1.final.jpg  (62 MB file)
FNORD

DrTskoul

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #9 on: January 18, 2017, 12:08:10 PM »
“You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts.”
― Richard P. Feynman

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #10 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/


@ 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.

oren

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #11 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
Although for some reason the images don't load for me at the moment.

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #12 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...

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #13 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
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.

DrTskoul

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #14 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
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...
“You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts.”
― Richard P. Feynman

crandles

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #15 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.

oren

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #16 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.

Tor Bejnar

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #17 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.
Arctic ice is healthy for children and other living things.

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #18 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/

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

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

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 ..."

Tor Bejnar

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #19 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!
Arctic ice is healthy for children and other living things.

crandles

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #20 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.

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #21 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

oren

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #22 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.

iwantatr8

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #23 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/
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/

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...
 

charles_oil

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #24 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.

charles_oil

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #25 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

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #26 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.

oren

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #27 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.

Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #28 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...


Bill Fothergill

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #29 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/

bairgon

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #30 on: February 03, 2017, 06:59:35 AM »
Video of the move at

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".

maga

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #31 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.

charles_oil

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #32 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 .....

Anne

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #33 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

charles_oil

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Re: Halley base shut down and new crack in Brunt shelf
« Reply #34 on: June 13, 2017, 02:56:33 PM »

sadly not from outside the UK  :(