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Messages - iwantatr8

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1
Here's a nice clear Sentinel Image of the Petermann.


2
It's always nice to start the season with a couple of clear Sentinel Images so to help everyone's habit.... ;)

4
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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.


5
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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...


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

8
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

9
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and an interesting article published in October - read it now before it becomes outdated news.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

10
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.
 

11
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...

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


13
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...

14
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. 

15
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

18
Arctic sea ice / Re: The 2018 melting season
« on: August 21, 2018, 04:56:33 PM »
As confirmation of something that we have been observing for a few years now, Nature has an article on arctic amplification and how the temperature differential reduction in summer is causing more set weather patterns.

https://doi.org/10.1038/s41467-018-05256-8

Open access for all.

Same again next year?

19
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.

22
Antarctica / Re: Rift in Larsen C
« on: June 30, 2017, 12:35:28 PM »
Nasa's Landsat 8 has taken some nice thermal images of the crack.

visit the EO here to see the update:
https://earthobservatory.nasa.gov/IOTD/view.php?id=90481&src=eorss-iotd

23
Yes it's an astonishing image from the 13 showing a huge amount of surface water all over the ice sheet some is even very close to the calving face, though what this means is unclear for now.

It's worth reviewing your gain settings in the sentinel app i find that a gain of 0.4 is the best for viewing ice areas with. it really brings out a lot of detail in this area.
 :o


24
Antarctica / Re: Rift in Larsen C
« on: June 07, 2017, 12:23:06 PM »
I know that it's tempting to try and follow the crack visually but it's really difficult to do and the location that Tor highlights is actually where the crack ended last year.

Project midas use the differential between these sentinel images to work out the movement and hence where the crack ends. visually this is best represented by this tweet by professor Luckman
https://twitter.com/adrian_luckman/status/871060621810335748

As you will see the crack end is much further north on the shelf and close to the whole front of the shelf will become a berg.


25
Espen,
The expansion in the north branch occurred sometime over the winter, I'm not sure it's a surge or if the melange caused enough back pressure on the northern calving face to inhibit actual calving (which seems possible given the southern branch behavior) resulting in the advancing that we see to early April.

Sentinel 2 Animation of April @ JI below (this will probably need a click to animate)


26
Greenland and Arctic Circle / Re: Svalbard / Spitsbergen
« on: May 03, 2017, 02:10:17 PM »
It seems that Team MIDAS in addition to checking on the progress of Larson C are also reviewing the surging of glaciers.

Have a look at the latest animation from Professor Luckman

"The surge of Nathorstbreen, Svalbard, as seen by Envisat in Wide-Swath-Mode"

https://twitter.com/adrian_luckman/status/859419466987384837


28
Antarctica / Re: Rift in Larsen C
« on: March 07, 2017, 11:44:48 AM »
Tor,

If you look at the Sentinel 2 image from 15th Feb

http://apps.sentinel-hub.com/sentinel-playground/#lat=-67.70110969585656/lng=-61.219940185546875/zoom=10/preset=CUSTOM/layers=B05,B03,B02/maxcc=100/gain=0.3/gamma=1/time=2015-01-01|2017-02-15/cloudCorrection=replace/atmFilter=/evalscript=/showImage

It clearly shows that the end crack is much further north than the area where you have shown, the cloud cover in the last few weeks makes it difficult to track but it will be quite interesting to see if the summer has enough energy left to create the calving or if we will be waiting for next year.


29
Antarctica / Re: Rift in Larsen C
« on: February 19, 2017, 09:53:53 AM »
Nature has an article on the shelf stresses here:

http://www.nature.com/articles/ncomms4707

which contains the helpful image below, looks like a curve to the east can be expected soon.

30
35m per day seems fast at any time, especially considering the SAR data and updates from the ESA

Go here for more details.

http://www.cpom.ucl.ac.uk/csopr/iv/index.html?glacier_number=1&image_date=170110_170116#output

I will admit though that they seem to have difficulties in measuring speed close to the calving face.

31
Antarctica / Re: Melt water in Antarctica
« on: February 04, 2017, 09:40:42 AM »
Here's a quick animation from worldview
It certainly looks like it may start as sediment clouded water but it soon forms ice on top before being drawn away in the current.

32
Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« 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...
 

33
Antarctica / Re: Rift in Larsen C
« on: January 20, 2017, 02:07:05 PM »
Now this is an interesting tool for monitoring using Sentinel 2 images.

http://apps.sentinel-hub.com/sentinel-playground/#lat=-67.58776309484115/lng=-61.321563720703125/zoom=10/preset=CUSTOM/layers=B05,B03,B01/maxcc=8/gain=0.4/time=2015-01-01|2017-01-13/cloudCorrection=replace/colCor=SenCor/

34
Antarctica / Re: What's new in Antarctica ?
« on: January 20, 2017, 01:46:15 PM »
This looks like it might be a very useful resource for monitoring antartica data.

http://quantarctica.npolar.no/

but it's a bit big!


35
Antarctica / Re: Melt water in Antarctica
« on: January 18, 2017, 02:00:52 PM »
These folks have some historic data on this looking at daily melt but nothing for last year and this.

http://lgge.osug.fr/personnels/PICARD_Ghislain/melting/

36
Arctic sea ice / Re: 2016 Year end IJIS Extent predictions
« on: January 01, 2017, 11:30:44 PM »
Well it's all over now, but what an interesting couple of months it's been.

Given that 64 of the 103 voters got within 0.5m sqkm of the final outcome is indicative of the experience and knowledge that the forum provides.

2017 promises to be another extraordinarily year in the tale of sea ice, not only in the arctic but the Antarctic too.

All the best for 2017 everyone!

37
Antarctica / Re: PIG has calved
« on: December 27, 2016, 07:57:41 AM »
Looking at the latest sentinel here
http://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SSH_20161226T045115_30DF_S_1.final.jpg
(Warning large photo)
There appears to be a new crack starting 1/3 of the way back from the face to the larger crack we've been following.
A race now I feel, between this and the existing crack as to which will be the first to calve.
I'm not sure that we will see anything this year given the few days left but early January seems likely.

Sorry for the lack of an image, posting from a mobile.

38
I'm not sure this really belongs here but given our discussions on monitoring glacier speed using image tracking this seems appropriate.

The EO blog post features the results of an AGU paper looking at Landsat 8 images for tracking.

http://earthobservatory.nasa.gov/IOTD/view.php?id=89261&src=eorss-iotd

and the paper here:

http://www.sciencedirect.com/science/article/pii/S003442571530211X

39
Antarctica / Re: Rift in Larsen C
« on: November 24, 2016, 10:35:08 AM »
Well today's S1A imagery shows quite an extension to the crack compared to the October images, and that the already open portion of the crack is widening.

http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20161124T001525_594C_S_1.final.jpg

40
Arctic sea ice / 2016 Year end IJIS Extent predictions
« on: November 21, 2016, 08:25:11 AM »
Ok,
Being as things are so unusual this year and there's a few of us still hanging around to watch, lets have your predictions for the IJIS Arctic Sea Ice Extent Prediction for the end of the year.

Poll open to vote changes until 1st December.

 :o

41
...is the result of some sort of infrasonic resonance propagating back from the calving front in a softened semi liquid basal layer.
...

Er, No.

What you are looking at are the resultant flow features generated from the internal stresses associated with the changing velocity profile of a distinctly non-Newtonian fluid.

Look here http://www.cpom.ucl.ac.uk/csopr/iv/index.html?glacier_number=0&image_date=160414_160508#output
for details of how rapidly the flow velocity changes both across and along the direction of flow.

Then try a couple of free access papers on glacier flow.

https://www.researchgate.net/profile/Gudmundur_Gudmundsson/publication/252424512_Basal_flow_characteristics_of_a_non-linear_flow_sliding_frictionless_over_strongly_undulating_bedrock/links/00463537a060cd6757000000.pdf

http://www.cpom.org/research/jad-ag.pdf
 

42

(And, btw, what is that dirty line, anyway?  It is so persistent, one could even speculate that it was an oil slick.  How can it be coming out black (or dark) like that for so long?  Maybe y'all have already discussed this somewhere, but I missed it.)
Posts around #285 cover that area in detail, continuous movement but no real change in the area since 2014.

43
Wow Indeed!

Fortunately the Sentinal 1A images are back at Polar View
http://www.polarview.aq/arctic

And a crop from yesterdays clear image gives us...

44
Arctic sea ice / Re: The 2016 melting season
« on: June 28, 2016, 08:21:29 AM »
I don't know if this has shown up elsewhere, but NSIDC has a new prototype product for sea ice concentration:

https://nsidc.org/data/docs/noaa/g10005-masam2/

A quick forum search suggests not, so thanks for finding it!
latest image from a couple of days ago here:
ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G10005/BrowseData/2016/masam2-20160625.png

One to add to the daily ASI graphs perhaps.


45
No drama at the calving front and none imminent. It appears that about half of the bergs are discharged from the north side. That does not mean half the volume (as we see only the surface and not freeboard) as they don't have the depth of the bergs from the main channel. The north side is responding to removal of buttressing as the main calving front retreats.


I hate to say this A-Team but it appears that there is some drama going on, looks like something happened yesterday given the changes in calving face and the Fjord.
 https://worldview.earthdata.nasa.gov/?p=arctic&l=MODIS_Terra_CorrectedReflectance_Bands721,MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&t=2016-06-21&v=-312303.6758297126,-2350251.7529409253,-66543.67582971259,-2219819.7529409253

Landsat seems to have (amazingly,given coverage this year so far) a pretty clear view of things.
http://earthexplorer.usgs.gov/browse/landsat_8/2016/082/233/LC80822332016174LGN00.jpg

46
Arctic sea ice / Re: The 2016 melting season
« on: May 20, 2016, 03:29:51 PM »
Nasa's Earth Observatory posts on the beaufort breakup here:
http://earthobservatory.nasa.gov/IOTD/view.php?id=88065&src=eorss-iotd

with an interesting first link in the further reading...

47
Greenland and Arctic Circle / Re: North Atlantic Cold Spot
« on: May 20, 2016, 03:03:17 PM »

49
Greenland and Arctic Circle / North Atlantic Cold Spot
« on: April 15, 2016, 10:21:22 PM »
Hi Folks,

I thought that as here has been a lot of discussion over in the consequences forum over the Hansen et al paper https://forum.arctic-sea-ice.net/index.php/topic,1327.0.html perhaps it's time to start reviewing the situation with regards to the north atlantic cold spot.

On the basis that this cold area is formed by the meltwater from all our favorite glaciers here on the Greenland forum I thought that this was the best place to start collecting data.
Starting with some SST anomolies

A.

 

50
My thoughts on this is that we have a very complex non-Newtonian fluid interaction taking place.

But starting with the base interactions we have an ice stream, for want of better explanation acting along the main glacier flow with turbulent interactions at the side of the channel.

The second influence is the descending ice that is falling over the mound.

The falling ice causes pressure at the edge of the turbulent flow from the main stream this pressure will give rise to a turning moment which overturns the edge of the stream. This is then pulled along with the rest of the stream causing an elongated feature along the edge.
I imagine this like a horizontal vortex acting along the ice stream edge but happening very slowly.

Just my theory.
A

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