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lurkalot

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Re: Rift in Larsen C
« Reply #150 on: July 12, 2017, 11:10:07 AM »
BBC reporting that it has detached: http://www.bbc.co.uk/news/science-environment-40321674

Andreas T

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Re: Rift in Larsen C
« Reply #151 on: July 12, 2017, 12:49:44 PM »
yes the AQUA nighttime band31 https://go.nasa.gov/2u8atAA is pretty definite. Lighter colour shows warmer (than ice  surface) seawater in the crack which given the low resolution of the thermal IR band is fairly wide (or does the low resolution make it appear wider?)
« Last Edit: July 12, 2017, 12:57:28 PM by Andreas T »

Seumas

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Re: Rift in Larsen C
« Reply #152 on: July 12, 2017, 01:08:43 PM »
My guess is that Larsen C ice shelf will have a major calving event in the next 5 +/- 3 years.

Technically correct, but right at the bottom end. Clearly you're too conservative with your predictions!  ;)

Project Midas has the full report: http://www.projectmidas.org/blog/calving/

oren

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Re: Rift in Larsen C
« Reply #153 on: July 12, 2017, 01:24:34 PM »
ASLR is too conservative. That is a scary thought indeed.

crandles

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Re: Rift in Larsen C
« Reply #154 on: July 12, 2017, 01:35:01 PM »
Quote
There was some keen interest a while back when the crack, which spread across the shelf from a pinning point known as the Gipps Ice Rise, looked as though it might sweep around behind another such anchor called the Bawden Ice Rise. Had that happened, it could have prompted a significant speed-up in the shelf's seaward movement once the berg came off.

As it is, scientists are not now expecting a big change in the speed of the ice.

Hadn't appreciated that where it broke off mattered so much.

DoomInTheUK

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Re: Rift in Larsen C
« Reply #155 on: July 12, 2017, 01:41:46 PM »

Hadn't appreciated that where it broke off mattered so much.

I get the feeling that it's more 'hope' than 'know'. We'll get a better idea of how much it matters in a year or so.....I'm still trying to work out how much Gin I'll need.

wili

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Re: Rift in Larsen C
« Reply #156 on: July 12, 2017, 02:49:52 PM »
Guardian is on it now, too: https://www.theguardian.com/world/2017/jul/12/giant-antarctic-iceberg-breaks-free-of-larsen-c-ice-shelf

Iceberg twice size of Luxembourg breaks off Antarctic ice shelf

Satellite data confirms ‘calving’ of trillion-tonne, 5,800 sq km iceberg from the Larsen C ice shelf, dramatically altering the landscape


Quote
A giant iceberg twice the size of Luxembourg has broken off an ice shelf on the Antarctic peninsula and is now adrift in the Weddell Sea.

Reported to be “hanging by a thread” last month, the trillion-tonne iceberg was found to have split off from the Larsen C segment of the Larsen ice shelf on Wednesday morning after scientists examined the latest satellite data from the area.

The Larsen C ice shelf is more than 12% smaller in area than before the iceberg broke off – or “calved” – an event that researchers say has changed the landscape of the Antarctic peninsula and left the Larsen C ice shelf at its lowest extent ever recorded.
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

Thomas Barlow

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Re: Rift in Larsen C
« Reply #157 on: July 12, 2017, 02:56:17 PM »

Iceberg twice size of Luxembourg breaks off Antarctic ice shelf

Quote
A giant iceberg twice the size of Luxembourg has broken off an ice shelf on the Antarctic peninsula and is now adrift in the Weddell Sea.


Yup. There it goes.
(from my screenshot of NASA Worldview today)
« Last Edit: July 12, 2017, 05:48:06 PM by Thomas Barlow »

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Re: Rift in Larsen C
« Reply #158 on: July 12, 2017, 02:59:59 PM »
.

VeliAlbertKallio

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Re: Rift in Larsen C
« Reply #159 on: July 12, 2017, 10:57:16 PM »
Larsen A --> Larsen B --> Larsen C --> Ronne Ice Shelf. It is a tragedy.  :'( 20 years maximum for R & R.  :(  I cannot see any reason that these chippings would end here but ever shoutwards...

Once upon a time was the Year 1995 and a fellow called Larsen Alpha: Statement on Ice Failure by Juan Pedro Brückner, the Director of the Argentinean Matienzo Base in Antarctica (attached).

Ban ki-Moon is always with us!  ??? He so much wanted climate to be on Rio+20 summit in 2012. I am enclosing his Larsen Beta statement as an image here.

I gave evidence on sea level rise risk (a good collection of links for Parliamentarians to browse many varied new phenomena - many familiar from here in ASIF, few others not yet discussed in ASIF): https://www.academia.edu/33000316/MPs_to_review_UKs_role_in_Arctic_sustainability_-_24th_April_2017.docx
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AbruptSLR

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Re: Rift in Larsen C
« Reply #160 on: July 12, 2017, 11:49:22 PM »
ASLR is too conservative. That is a scary thought indeed.

The referenced post was from March 2015, so 5 +/- 3 years would be from March 2017 to March 2023, so at least the calving was within my margin of error ;)
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RoxTheGeologist

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Re: Rift in Larsen C
« Reply #161 on: July 13, 2017, 01:19:39 AM »

Time to lock this thread....:)?

Juan C. García

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Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Thomas Barlow

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Re: Rift in Larsen C
« Reply #163 on: July 13, 2017, 02:10:00 AM »

Time to lock this thread....:)?
No. Where will it go? Will it break up? Who owns it?

Csnavywx

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Re: Rift in Larsen C
« Reply #164 on: July 13, 2017, 02:23:53 AM »
ASLR is too conservative. That is a scary thought indeed.

The referenced post was from March 2015, so 5 +/- 3 years would be from March 2017 to March 2023, so at least the calving was within my margin of error ;)

This officially leaves the shelf in a concave formation. With the re-arrival of the +PDO/+ENSO favored phase and the encroachment of the -9C annual isotherm on the shelf, the time of stability for Larsen C may be running out.

AbruptSLR

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Re: Rift in Larsen C
« Reply #165 on: July 13, 2017, 03:16:04 AM »
ASLR is too conservative. That is a scary thought indeed.

The referenced post was from March 2015, so 5 +/- 3 years would be from March 2017 to March 2023, so at least the calving was within my margin of error ;)

This officially leaves the shelf in a concave formation. With the re-arrival of the +PDO/+ENSO favored phase and the encroachment of the -9C annual isotherm on the shelf, the time of stability for Larsen C may be running out.

Maybe the rest of the ice shelf will collapse before my March 2023 timeframe ends. :o
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RobertM

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Re: Rift in Larsen C
« Reply #166 on: July 13, 2017, 03:43:17 AM »
Greetings ASIF, long time lurker here, moved to post by the Larsen C event!

It is fascinating to read the media reaction: many glaciologists seem to be falling over themselves to say there is no reason to think there is any connect to climate change here. I find that weird. Anyway, what I wanted to ask about is this. Dr Adrian Luckman has several times cited a 2015 Scripps study (e.g., in today's Guardian and in theconversation.com) as measuring thickening of Larsen C. As I read the study, it says Larsen C is thinning:

"Volume loss from Antarctic ice shelves is accelerating",  Paolo et al Science, 2015: "On the eastern side of the Antarctic Peninsula... the regional ice-shelf thinning rate of 3.8 ± 1.1 m/decade is about half of that on the western side. The onset of thinning for Larsen C has progressed southward, which is consistent with climate-driven forcing discussed in earlier studies. The highest thinning rates on Larsen C (with local maximum thinning of 16.6 ± 8.1 m/decade) are near Bawden Ice Rise."

The Bawden Ice Rise is exactly where the iceberg finally detached.

Secondly, until today I was following the Larsen C rift in the context of John Mercer's 1978 predictions. Today I looked into it a little more. The detachment point is around the -12C isotherm (https://www.researchgate.net/publication/240424228_Holocene_climate_and_glacial_history_of_the_northeastern_Antarctic_Peninsula_The_marine_sedimentary_record_from_a_long_SHALDRIL_core), whereas the shelves that have collapsed or started to collapse, consistent with Mercer's theory, to the north and west, are all markedly warmer, above the -9 C isotherm. The newspaper articles say there are no reports of surface meltwater on Larsen C.

So my question is, is there any mechanism by which warming of the air, even if it remains below freezing for most of the summer, could have weakened the shelf and contributed in some way?

Pmt111500

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Re: Rift in Larsen C
« Reply #167 on: July 13, 2017, 05:09:51 AM »
Proposing the name 'Reagan Iceberg' for the piece of ice shelf that irreversibly separated from the glaciers of West Antarctica. This would be because of the slow pace of heat accumulation in the ocean, the 'thermal inertia' which is too technical an expression for many. This just means that the water takes a while to warm up and the heat that was applied in 1980s would have done the same, though a bit later, possibly in 2030s. Thus we could expect the "Iceberg Tillerson of Drumpfistan" to be launched by the chinese conspirators in 2040s. This would be way larger since the ego size and stupidity difference.

CraigsIsland

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Re: Rift in Larsen C
« Reply #168 on: July 13, 2017, 08:03:57 AM »
ASLR is too conservative. That is a scary thought indeed.

The referenced post was from March 2015, so 5 +/- 3 years would be from March 2017 to March 2023, so at least the calving was within my margin of error ;)

Jeez. I was hoping the scary stuff from Antarctica and Greenland would’ve been decades out. Like 5+ feet after 2040 maybe.

Are you surprised by this break? What’s the next “big” event In Antarctica?

This officially leaves the shelf in a concave formation. With the re-arrival of the +PDO/+ENSO favored phase and the encroachment of the -9C annual isotherm on the shelf, the time of stability for Larsen C may be running out.

Maybe the rest of the ice shelf will collapse before my March 2023 timeframe ends. :o

AbruptSLR

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Re: Rift in Larsen C
« Reply #169 on: July 13, 2017, 10:30:34 AM »
Are you surprised by this break? What’s the next “big” event In Antarctica?

I believe that the next "big' event in Antarctica will be a major calving event for the Pine Island Ice Shelf within the next one to nine months.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Adam Ash

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Re: Rift in Larsen C
« Reply #170 on: July 13, 2017, 10:42:34 AM »
Thinking out loud... (sorry!)
While a naive view of the impact of this calving would be to see the remainder of the ice shelf do a prompt shuffle to the east, relieving buttressing on land-based ice, I guess the major effect will be increased exposure of the remainder of the ice shelf to open-ocean tidal and thermal dynamics. 

It will be interesting to watch for signs of the prompt disintegration of the remainder (which seems unlikely at this stage) and instead I guess we will just continue to see the edge chewed away. 

Is there any feature of the ocean floor shape which would alter current dynamics now the calving is done? 

It will be interesting to watch the berg's movement from here - it will give us an idea of the net outcome of currents etc acting on it.

Another sign of the times!

AbruptSLR

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Re: Rift in Larsen C
« Reply #171 on: July 13, 2017, 11:12:48 AM »
For those who are not aware, more background discussion on trends for Larsen C can be found in the linked thread entitled: "Discussion of the Antarctic Peninsula"

http://forum.arctic-sea-ice.net/index.php/topic,322.0.html

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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numerobis

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Re: Rift in Larsen C
« Reply #172 on: July 13, 2017, 01:46:29 PM »
RobertM: on the march for science Facebook post, Robert Grumbine mentioned the in-retrospect obvious point that the temperature at the base is barely freezing, while at the surface it's very cold. So there's a temperature gradient through the ice shelf.

Higher temperature at the surface, even a warming from -35 to -30, means a larger region inside the slab of ice that's "warm" and therefore "soft" (in relative term of course), which means it can move faster.

Adam Ash

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Re: Rift in Larsen C
« Reply #173 on: July 13, 2017, 02:41:05 PM »
https://www.space.com/37472-nasa-images-show-massive-iceberg-separation.html?utm_source=notification

This site shows a good time series of the crack's development.  The ice further inland is none too cohesive, with numerous cracks parallel to the current break line showing over recent years. 

It looks more like the ice shelf is held in position by shore-ward currents than any great degree of internal connectivity.

Thomas Barlow

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Re: Rift in Larsen C
« Reply #174 on: July 13, 2017, 02:54:36 PM »
Greetings ASIF, long time lurker here, moved to post by the Larsen C event!

It is fascinating to read the media reaction: many glaciologists seem to be falling over themselves to say there is no reason to think there is any connect to climate change here. I find that weird.

Yes, it would be abnormal if there was no such thing as global warming going on.

magnamentis

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Re: Rift in Larsen C
« Reply #175 on: July 13, 2017, 08:47:39 PM »

Time to lock this thread....:)?

better to amend the name as it was done with the US election thread so that the content remains accessible within the same thread and the discussion will continue seamlessly, this is my proposal, others will make the choice.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #176 on: July 13, 2017, 09:41:06 PM »
A June 6, 2017 PolarView image seems to show less detail, but looking at the ice shelf coast in the area where the rift is likely to go (or went), I think I see (yes: speculation) a lineation at the coast (middle arrow in 'whiter ice' June 6 image) that is not pared with a lineation on the June 4 image ([see June 8 post]).  (The other two pairs of arrows identify duplicated lineations.)  ...
The actual rift (July 12 PolarView) reached the edge approximately where my 'middle' arrow identified a new lineation.  Cool!  (Chance?) (images are approximately the same area)
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #177 on: July 13, 2017, 09:54:30 PM »
Here is 'just the rift end' at 106%.  From the June 8 post's scale, the rift at its end is about 1/2 km wide. Now looking forward to all the 'little' icebergs that we were 'promised'!
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VeliAlbertKallio

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Re: Rift in Larsen C
« Reply #178 on: July 14, 2017, 12:55:15 AM »
Does anyone know whether 10,000 km2 has been added to the global sea ice area to offset the lost segment of Larsen C ice shelf. When it will be included in the global sea ice area, if not already?  ???
"Setting off atomic bombs is considered socially pungent as the years are made of fleeting ice that are painted by the piling up of the rays of the sun."

Peter Ellis

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Re: Rift in Larsen C
« Reply #179 on: July 14, 2017, 01:54:09 AM »
Does anyone know whether 10,000 km2 has been added to the global sea ice area to offset the lost segment of Larsen C ice shelf. When it will be included in the global sea ice area, if not already?  ???
Global sea ice area is currently 14.75 million (Antarctic) plus 8.04 million (Arctic) = 22.79 million km^2. Feel free to mentally add 10,000 km^2 to make 22.80 million instead.

It changes global sea ice area by less than one twentieth of one percent.

VeliAlbertKallio

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Re: Rift in Larsen C
« Reply #180 on: July 14, 2017, 10:52:03 AM »
I am aware of that but the figures given by many sites for sea ice go to the last decimal points. There are a lot more ice shelves to go and for the Weddel and Ross Seas the overall percentage is very high. For the same argument we could just omit CAA and the Black Sea / Caspian Sea / Baltic Sea NH sea ice figure but to my understanding, these are calculated to overall winter tally.

Does anyone know whether 10,000 km2 has been added to the global sea ice area to offset the lost segment of Larsen C ice shelf. When it will be included in the global sea ice area, if not already?  ???
Global sea ice area is currently 14.75 million (Antarctic) plus 8.04 million (Arctic) = 22.79 million km^2. Feel free to mentally add 10,000 km^2 to make 22.80 million instead.

It changes global sea ice area by less than one twentieth of one percent.
"Setting off atomic bombs is considered socially pungent as the years are made of fleeting ice that are painted by the piling up of the rays of the sun."

FredBear

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Re: Rift in Larsen C
« Reply #181 on: July 14, 2017, 01:35:10 PM »
   .   .   .   but VeliAlbertKallio the satellites have difficulty even with meltponds!! (& clouds, & coastlines, & 15% cut-offs, etc.).I'm sure we can live with the limitations. It is only 12% of the 4th largest iceshelf on the earth  .   .   .   there's bigger nits to pick?

Pmt111500

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Re: Rift in Larsen C
« Reply #182 on: July 14, 2017, 01:43:57 PM »
It would be kind of fun if the sea ice charts would show 'very old ice' with an estimate of years to develop to such a berg. I guess in this case there should be a number of over at least 8200. Probably much more.

oren

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Re: Rift in Larsen C
« Reply #183 on: July 14, 2017, 01:49:20 PM »
VAK, I think the direct answer to your question is: when the land mask is updated. Have no clue when that might happen though.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #184 on: July 14, 2017, 03:35:28 PM »
A screen shot from the middle of the rift (July 12 PolarView) very nicely shows the relative movement of the iceberg and the ice shelf: a classic transverse fault.  All arrows are parallel and the three sets of collinear arrows have the same spacing between their butt ends.  (Is there some deformation in the iceberg or is my arrows' angle slightly off?)
« Last Edit: July 15, 2017, 10:27:09 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Shared Humanity

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Re: Rift in Larsen C
« Reply #185 on: July 15, 2017, 05:10:54 PM »
Could the movement of the ice berg be caused by currents in the Weddell Sea? Are there persistent southerly currents down the peninsula toward the Ronne Ice Shelf?

Shared Humanity

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Re: Rift in Larsen C
« Reply #186 on: July 15, 2017, 05:14:03 PM »
Oh. And what the heck is with all of the penguins on this map?

Shared Humanity

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Re: Rift in Larsen C
« Reply #187 on: July 15, 2017, 05:18:31 PM »
It would appear that the ocean currents actually flow north along the peninsula.

Forest Dweller

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Re: Rift in Larsen C
« Reply #188 on: July 15, 2017, 07:40:20 PM »
Here is 'just the rift end' at 106%.  From the June 8 post's scale, the rift at its end is about 1/2 km wide. Now looking forward to all the 'little' icebergs that we were 'promised'!

Cool image.
The chunk of ice in the middle shows it came from above so there must be a surface flow heading south.
Some slushy ice entering the crack as well further indicates that.
The little map posted above has the currents heading north however.
Guess not at the surface...

johnm33

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Re: Rift in Larsen C
« Reply #189 on: July 15, 2017, 08:11:50 PM »

The dark blue circles are the amphidromic points, around which the tides turn clockwise. I believe they drive the currents, that is the currents are residual persistent flows driven by tidal movements.
Image from http://www.esr.org/ptm_index.html

charles_oil

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Re: Rift in Larsen C
« Reply #190 on: July 16, 2017, 10:56:43 AM »

Tor Bejnar

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Re: Rift in Larsen C
« Reply #191 on: July 16, 2017, 10:41:51 PM »
The July 16 Sentinel image from PolarView shows the south end of the rift.  This screen shot is at 50% enlargement ("ensmallment"?)
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Hefaistos

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Re: Rift in Larsen C
« Reply #192 on: July 17, 2017, 05:33:38 PM »
Starts to break up now on the edge, according to satellite imagery from Deimos Imaging.

https://www.rt.com/viral/396558-larsen-c-iceberg-satellite/

Tor Bejnar

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Re: Rift in Larsen C
« Reply #193 on: July 19, 2017, 05:52:50 PM »
There appears to be some fast ice growing in the young rift between Larsen C and Iceberg A68 (and friends). PolarView screen print.
Project MIDAS offers this (screen shot of part of their post's graphic with scale moved and Iceberg label recreated):
Quote
... a new rift appears to be extending northwards (towards the top left) and may result in further ice shelf area loss. Although this new rift will probably soon turn towards the shelf edge, there may be a risk that it will continue on to Bawden Ice Rise, a crucial point of stabilisation for Larsen C Ice Shelf.
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

magnamentis

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Re: Rift in Larsen C
« Reply #194 on: July 19, 2017, 11:02:28 PM »
@Tor Bejnar

is "fast ice" the correct term for ice growing between an iceberg and an ice-shelf?

the question is mean seriously not that you think there would be sarcasm or something i just don't know and like to learn about terms as much as i can, this term just did never cross my mind in this context, hence your feedback will be very appreciated.

charles_oil

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Re: Rift in Larsen C
« Reply #195 on: July 19, 2017, 11:46:48 PM »

Tor Bejnar

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Re: Rift in Larsen C
« Reply #196 on: July 20, 2017, 12:22:18 AM »
fast ice
Quote
ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents.

The new ice attached to (and growing off of) the Larsen C ice shelf is fast ice.  The new ice that is attached to the iceberg (ice island) is not fast ice, as long as the iceberg is drifting around.  If the iceberg stops moving for a bit, there will temporarily (at least) fast ice between the two.  I rather expect the iceberg to get stuck in the winter fast ice later this SH winter. (But I'm not an iceberg expert.)
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

magnamentis

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Re: Rift in Larsen C
« Reply #197 on: July 20, 2017, 01:33:32 AM »
thanks, before learning this i thought fast ice is fastened to land which apparently was wrong ;)

Tor Bejnar

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Re: Rift in Larsen C
« Reply #198 on: July 21, 2017, 06:51:15 PM »
Iceberg A68 is wrecking havoc on the frozen sea ice off of Larsen C Ice Shelf: at least for now.  The crack through the fast ice shown here (PolarView 11 pm on July 18) isn't apparent on the 8 am image (posted above).  It is interesting to see how much the little icebergs have moved in 15 hours.  The largest of the small icebergs is about 5 x 12 km in size.
« Last Edit: July 21, 2017, 06:58:17 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

solartim27

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Re: Rift in Larsen C
« Reply #199 on: July 22, 2017, 05:25:27 PM »
The rifts behind the initial crack show signs of widening.  This could get interesting fast (or not).  28 Jun to 22 Jul  Click required, then you'll want to zoom in

S1A_EW_GRDM_1SSH_20170722T001458_4661_S_1.final.jpg
S1A_EW_GRDM_1SSH_20170628T001457_3D5F_S_1.final.jpg
« Last Edit: July 22, 2017, 05:35:04 PM by solartim27 »
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