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Messages - iwantatr8

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1
With all the clear sky we have been seeing recently I couldn't resist putting together an animation of the last month's movements.

2
Missed  this with the earlier image of 79N

It's got a loose tooth...  A stress crack has opened up near one of the pinning islands at the front.

3
Here's a nice clear Sentinel Image of the Petermann.


4
It's always nice to start the season with a couple of clear Sentinel Images so to help everyone's habit.... ;)

6
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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


7
There's an interesting article from cryosphere looking at using machine learning to track calving faces through SAR products - which has the potential to support the overall tracking of major calvings in greenland and antarctica.

https://www.the-cryosphere-discuss.net/tc-2019-14/tc-2019-14.pdf

8
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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and an interesting article published in October - read it now before it becomes outdated news.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

9
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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.
 

10
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« on: December 13, 2018, 05:35:37 PM »
Looks like Chasm 1 has advanced some more - very close to calving now...

11
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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
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...

12
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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. 

13
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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

15
That is an interesting crack feature - I wonder how long it's been there...

there's a paper about this see https://pdfs.semanticscholar.org/858b/259fafbcb9b76022b7358d6ea74d6f6cc67d.pdf

It's primarily related to Ice shelves in the Antarctic but from the conclusions
"Our approach could be expanded to the simulation of fast-flowing ice streams, to capture the manifold observed mechanical decoupling from the side margins and hence a possibly stronger response of the plug-like flow to perturbations"

Apparently and logically more cracks = less friction = faster flow.  The evolution of the crack field and the exposure of more of it through melt has been one of the more fascinating things to watch over the years.

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