Support the Arctic Sea Ice Forum and Blog

Author Topic: Larsen C Ice Shelf  (Read 185497 times)

AbruptSLR

  • Multi-year ice
  • Posts: 19703
    • View Profile
  • Liked: 2268
  • Likes Given: 286
Re: Rift in Larsen C
« Reply #100 on: May 03, 2017, 04:20:36 PM »

https://www.eurekalert.org/pub_releases/2017-05/su-air050217.php

https://scienceblog.com/493824/larsen-c-antarctic-ice-rift-spreads/

The linked articles note the rift in the Larsen C ice shelf in Antarctica now has a second branch, which is moving in the direction of the ice front.  "While the previous rift tip has not advanced, a new branch of the rift has been initiated. This is approximately 10km behind the previous tip, heading towards the ice-front.  "This is the first significant change to the rift since February of this year. Although the rift length has been static for several months, it has been steadily widening, at rates in excess of a metre per day."

As a follow-up, the linked article is entitled: "The Larsen C Ice Shelf Crack Just Sprouted a New Branch". 

http://www.climatecentral.org/news/larsen-c-crack-new-branch-21409

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

Shared Humanity

  • Guest
Re: Rift in Larsen C
« Reply #101 on: May 03, 2017, 07:54:21 PM »
If you look at the angle that new branch is heading towards the sea, it aligns perfectly with the ice shelf that is pinned by the small island to the north. This is exactly where the berg will break free.

Seumas

  • New ice
  • Posts: 36
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: Rift in Larsen C
« Reply #102 on: May 18, 2017, 04:47:32 PM »
An update from Project Midas as Larsen C begins to react to the rift:

http://www.projectmidas.org/blog/reacts-to-rift/

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #103 on: May 18, 2017, 06:21:39 PM »
Although still connected by a (twisting) neck, they are calling it an iceberg!  I think the falling-in rift edges is mostly a reflection of the instability of tall cliffs (especially tall cliffs with fractured rock [or ice] around.  The taller the shelf edge, the faster it will fail (more or less).
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Tony Mcleod

  • New ice
  • Posts: 94
    • View Profile
  • Liked: 25
  • Likes Given: 6
Re: Rift in Larsen C
« Reply #104 on: May 19, 2017, 02:06:09 AM »
Appears to the laymens eye those 'slumping' blocks can only wedge the crack further apart a they move.

1rover1

  • New ice
  • Posts: 29
    • View Profile
  • Liked: 22
  • Likes Given: 31
Re: Rift in Larsen C
« Reply #105 on: May 31, 2017, 06:48:29 PM »
The rift has grown by 17 km since May 25!
 
"In the largest jump since January, the rift in the Larsen C Ice Shelf has grown an additional 17 km (11 miles) between May 25 and May 31 2017. This has moved the rift tip to within 13 km (8 miles) of breaking all the way through to the ice front, producing one of the largest ever recorded icebergs. The rift tip appears also to have turned significantly towards the ice front, indicating that the time of calving is probably very close."

http://www.projectmidas.org/blog/another-step-closer/


Dry_Land_Is_Not_A_Myth

  • New ice
  • Posts: 10
    • View Profile
  • Liked: 3
  • Likes Given: 1
Re: Rift in Larsen C
« Reply #106 on: June 01, 2017, 04:09:48 AM »
When this detaches any thoughts on if it will no longer be counted in the nsidc Antarctic Sea Ice Extent? I've found size estimates that the ~2000 m^2 (~5000 km^2, to 1 sig fig), so it probably won't cause a notable dip in sea ice extent which is ~7 million km^2 (to 1 sig fig) if it was counted.

bairgon

  • Frazil ice
  • Posts: 133
    • View Profile
  • Liked: 15
  • Likes Given: 0
Re: Rift in Larsen C
« Reply #107 on: June 01, 2017, 07:03:28 AM »
See earlier in the thread for a discussion about that:

Apologies if this has been asked before....but is the Larsen C INCLUDED in the "sea ice" numbers....or are the ice shelve's NOT included in the sea ice numbers?

Lord M Vader

  • Nilas ice
  • Posts: 1406
    • View Profile
  • Liked: 60
  • Likes Given: 39
Re: Rift in Larsen C
« Reply #108 on: June 01, 2017, 07:44:39 PM »

georged

  • New ice
  • Posts: 52
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: Rift in Larsen C
« Reply #109 on: June 04, 2017, 07:46:48 AM »
Larsen C is on the verge to break off: http://www.climatecentral.org/news/larsen-c-iceberg-breaking-off-21498

It's rocketing away. (EASO map below)

https://twitter.com/adrian_luckman/status/871060621810335748

Edit:

The Larsen Berg will be about the size of the Grand Canyon National Park or Delaware, or half the size of Puerto Rico when it is released, for context.
« Last Edit: June 04, 2017, 08:10:28 AM by georged »

solartim27

  • Grease ice
  • Posts: 599
    • View Profile
  • Liked: 42
  • Likes Given: 74
Re: Rift in Larsen C
« Reply #110 on: June 04, 2017, 08:57:24 AM »
Here's a gif of the area from 17 Apr to 4 Jun.  Full size, so you'll need to click to animate and zoom in to the part you want to see (2.3 Mb).  The crack extension is barely discernable at this resolution.

http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20170604T001456_985B_S_1.final.jpg  (33 Mb)

S1A_EW_GRDM_1SSH_20170417T001453_DDEE_S_1.final.jpg (70 Mb)
FNORD

magnamentis

  • Guest
Re: Rift in Larsen C
« Reply #111 on: June 04, 2017, 05:47:20 PM »
Here's a gif of the area from 17 Apr to 4 Jun.  Full size, so you'll need to click to animate and zoom in to the part you want to see (2.3 Mb).  The crack extension is barely discernable at this resolution.

http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20170604T001456_985B_S_1.final.jpg  (33 Mb)

S1A_EW_GRDM_1SSH_20170417T001453_DDEE_S_1.final.jpg (70 Mb)

very nice, thanks, i think one can already guess where the growing fissure from the ocean in a 90 degree angle will meet the fissure that we're all watching for months now. it's clearly visible that the smaller ocean side fissure has grown into the shelf ice.

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #112 on: June 05, 2017, 10:38:38 PM »
PolarView has made an image from yesterday (2017-06-04) available.  Here are three screen prints (blow-ups) showing the rift's right hand turn and it's relative position to the Larsen C shelf.  (Arrows point to the sharp curve.  Circles identify a 'blemish' on the rift. Location rectangles are approximate.)
EDIT: The crack end progressed beyond the edge of the middle image (near the upper left corner) and way beyond the blow-up image.  The bend I identified is false!  and is where the rift ended about a year ago.
« Last Edit: June 07, 2017, 04:39:25 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

georged

  • New ice
  • Posts: 52
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: Rift in Larsen C
« Reply #113 on: June 06, 2017, 02:00:10 AM »
PolarView has made an image from yesterday (2017-06-04) available.  Here are three screen prints (blow-ups) showing the rift's right hand turn and it's relative position to the Larsen C shelf.  (Arrows point to the sharp curve.  Circles identify a 'blemish' on the rift. Location rectangles are approximate.)

Fascinating. Apologies if this has been asked, but how stable/active is the large rift below the Larsen Berg?

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #114 on: June 06, 2017, 04:48:50 AM »
I don't understand what you are asking ("Larsen berg" = 'Larsen C almost-a-berg'?), but if I did, I'm sure I wouldn't know.  I hope someone else can help!
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

magnamentis

  • Guest
Re: Rift in Larsen C
« Reply #115 on: June 06, 2017, 07:36:30 PM »
let's see :-)

there are several other possibilities but this one's at list seamlessly connected ;)

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #116 on: June 06, 2017, 08:24:59 PM »
I was thinking along similar lines.  I see several lineations that might reflect zones of weakness leading to the coast (purple's), and there are the parallel-to-the-coast cracks (a couple green's drawn in) that could be incorporated in a 'final' rift path. EDIT: note: the rift's end is beyond the upper left corner of this image. (The suggested 'end' is where it ended a year ago.)
« Last Edit: June 07, 2017, 04:59:00 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

magnamentis

  • Guest
Re: Rift in Larsen C
« Reply #117 on: June 07, 2017, 01:17:37 AM »
I was thinking along similar lines.  I see several lineations that might reflect zones of weakness leading to the coast (purple's), and there are the parallel-to-the-coast cracks (a couple green's drawn in) that could be incorporated in a 'final' rift path.

absolutely, it's all there, just for the fun of it i thought to lean out of the window a bit more than necessary, game on LOL. further i don't really like the "i knew it" stuff while avoiding the risk to
express those thoughts in advance, prefer to stand corrected by reality.

i think that there will be some scrambling along the final breaking lines, however, interesting to watch this coming :-)

iwantatr8

  • New ice
  • Posts: 79
    • View Profile
  • Liked: 21
  • Likes Given: 4
Re: Rift in Larsen C
« Reply #118 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.


magnamentis

  • Guest
Re: Rift in Larsen C
« Reply #119 on: June 07, 2017, 04:18:29 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.

thanks for that input, seems more plausible because things are more smooth in that theory :-)
i just lack the profound knowhow to do more than guessing and/or following visible lines LOL

looking at this from the outside ( like turning the chessboard 180dg ;) i'd vote for the variant you provided, let's see, interesting all the way down till things happen which could take another while BTW.

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #120 on: June 07, 2017, 06:17:36 PM »
Thank you, iwantatr8, for pointing out my error.  (I've made "edit" notes in the previous posts.) The attached three screen prints show
1) the Larsen C shelf from PolarView (June 4, 2017 - same as my previous post) with a purple circle showing the general location of the real rift end plus a scale (and red box where I previously thought the rift ended)
2) the map published by MIDAS on May 31 with an added scale
3) close up of the Larsen C shelf where the rift ends with solid arrows pointing to the rift and dashed arrows showing where the rift might be (two suggested paths are within the red rectangle).
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #121 on: June 08, 2017, 04:49:54 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 (dashed arrow).  (The other two pairs of arrows identify duplicated lineations.)  On the "rift-end" June 6 (wider area) image, I discern a few curved lineations within the red location box, one of which might identify the late May hook. (June 6 and June 4 images are approximately to same scale and location, and location box is also approximate.)

I sure look forward to the next MIDAS feed!
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Thomas Barlow

  • Guest
Re: Rift in Larsen C
« Reply #122 on: June 16, 2017, 02:33:10 PM »
This is the latest from Polar View.
Looks like the crack to the right of the rock is also opening up more?

Hans

  • New ice
  • Posts: 24
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: Rift in Larsen C
« Reply #123 on: June 21, 2017, 03:38:23 PM »
According the Dutch news site nu.nl: "Scientists issued a warning on Wednesday to ships in Antarctica in the coming days. A giant ice plateau, as big as the island of Bali, is about to break loose."

Project Midas is mentioned in the text, but unclear to me who "the scientist" are.
Anybody knows a real source?
link :http://www.nu.nl/klimaat/4783929/schepen-bij-antarctica-gewaarschuwd-enorm-scheurend-ijsplateau.html

RikW

  • Frazil ice
  • Posts: 244
    • View Profile
  • Liked: 44
  • Likes Given: 19
Re: Rift in Larsen C
« Reply #124 on: June 21, 2017, 04:28:43 PM »
And I think they have some of the numbers wrong:

Google translate:
As soon as the plateau breaks out of Antarctica, the sea level rises to 'only' a few centimeters. If all the "fixed ice" breaks, an increase of about four meters is expected. And if all the ice is melting on the continent, the sea level can rise by tens of meters.

If I remember correctly: 10 cm happens when the ice-shelf completely collapses and the gletsjers that "end" in the shelf also stream into the sea.

4m happens when west-antarctica melts completely, isn't it?


And a stupid question, the shelf is said to be 350 meters thick, so around 50m above and 300m below sea level?

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #125 on: June 21, 2017, 05:22:41 PM »
Per Wikipedia, about 1/9th of an ice shelf is above water.  1/9th of 350 m is nearly 40m (or just over 125 feet, for us flatlander Americans)
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

RikW

  • Frazil ice
  • Posts: 244
    • View Profile
  • Liked: 44
  • Likes Given: 19
Re: Rift in Larsen C
« Reply #126 on: June 22, 2017, 02:39:12 PM »
according to the dutch wikipedia it's 1/5th till 1/7th

Dutch:
Wel is zeker dat een ijsberg slechts voor een vijfde tot een zevende boven water ligt

Google translate:
It is certain that an iceberg is only for a fifth to a seventh above water

Love those differences...

gerontocrat

  • Multi-year ice
  • Posts: 20288
    • View Profile
  • Liked: 5277
  • Likes Given: 69
Re: Rift in Larsen C
« Reply #127 on: June 22, 2017, 02:54:23 PM »
Would an iceberg float higher in seawater than in freshwater, especially if made of freshwater ?
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

oren

  • Moderator
  • First-year ice
  • Posts: 9799
    • View Profile
  • Liked: 3582
  • Likes Given: 3914
Re: Rift in Larsen C
« Reply #128 on: June 22, 2017, 05:18:14 PM »
Per Wikipedia, about 1/9th of an ice shelf is above water.  1/9th of 350 m is nearly 40m (or just over 125 feet, for us flatlander Americans)
The wiki quote:
Quote
The density contrast between glacial ice, which is denser than normal ice, and liquid water means that only about 1/9 of the floating ice is above the ocean surface.

There are several factors:
Freshwater is lighter than seawater.
But, shelf ice is denser than normal ice.
And the shape of the iceberg matters. A huge tabular iceberg is relatiely uniform, but a small calved iceberg could be assymetric with its top part narrower and therefore floating higher in the water.

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #129 on: June 22, 2017, 05:20:48 PM »
Per an internet search, some generic information:
Quote
What percent of the volume of the iceberg is under water?

Remember that the density of ice is 0.92 g/mL, and the density of water is 1.0 g/mL (1.03 for salt water). This means that ice has nine-tenths, or 90 percent of water's density – and so 90 percent of the iceberg is below the water's surface.

Freshwater:  .92/1.0 = 92% below water line
Saltwater: .92/1.03 = 89% below water line

So yes, an iceberg floats slightly higher in salt water.  If you really want to see a difference, take your piece of ice shelf to Great Salt Lake [Utah, USA] (~1.17 g/mL yielding 78% below water line - or instead of 40 m. showing, 75 m. will tower over you [after digging out the bottom of the lake, 'cause it is only on-the-order-of 10 m deep!]).
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

FishOutofWater

  • Nilas ice
  • Posts: 1088
    • View Profile
  • Liked: 696
  • Likes Given: 332
Re: Rift in Larsen C
« Reply #130 on: June 23, 2017, 02:15:27 PM »
Guardian article by an actual expert says that Larsen C detachment will happen within a few weeks, but is not attributing it to climate change. I will add that it's very tricky to determine if a natural process like iceberg formation in Antarctica is speeding up because of climate change. She thinks that this is a normal event.

So, while ice fracturing and surface melting may sound like signs of climate change in action in Antarctica, they are really part of the background against which we must look for real change. Real changes are happening there, and when we report them they need to stand out. Previous collapse events involved large amounts of surface melt that forms ponds on an ice shelf that had already weakened. We have not observed this on Larsen C. We will continue to monitor Antarctica by satellites and from the ground, but we will not cry wolf about an imminent collapse of Larsen C.

    Helen Amanda Fricker is a professor at the Scripps Institution of Oceanography


https://www.theguardian.com/science/2017/jun/23/melting-and-cracking-is-antarctica-falling-apart-climate-change



pileus

  • Grease ice
  • Posts: 536
    • View Profile
  • Liked: 45
  • Likes Given: 9
Re: Rift in Larsen C
« Reply #131 on: June 28, 2017, 06:45:07 PM »
Another update on the imminent event.

Antarctic ice shelf crack is moving at record speeds, poised to cleave off massive iceberg any minute

http://mashable.com/2017/06/28/antarctica-iceberg-larsen-c-ice-shelf.amp

In a June 28 blog post, the scientists report: "...The soon-to-be-iceberg part of [the] Larsen C Ice Shelf has tripled in speed to more than ten meters per day between 24th and 27th June 2017." This means that the crack has moved at least 33 feet per day during the course of this 4-day period.

This is "the highest speed ever recorded on this ice shelf," according to the researchers. Predicting the exact date that the iceberg will cleave off from the Antarctic continent is tricky, however, since it still remains attached to the ice shelf, but just barely.

"The iceberg remains attached to the ice shelf, but its outer end is moving at the highest speed ever recorded on this ice shelf," researchers wrote. "We still can’t tell when calving will occur -- it could be hours, days or weeks -- but this is a notable departure from previous observations."

The satellite scientists are depending on to detect changes in the progression of the fissure is known as Sentinel-1, a project of the European Space Agency. This satellite is able to detect subtle changes in ground movements and is used for both studying melting glaciers and ice shelves as well as earthquakes and other geological phenomena.

According to Project MIDAS scientists, the most recent data do not cover the tip of the ice rift, but a low resolution image taken just after midnight on June 28 "shows clearly that the iceberg remains attached to the ice shelf at its western end -- for now."

RikW

  • Frazil ice
  • Posts: 244
    • View Profile
  • Liked: 44
  • Likes Given: 19
Re: Rift in Larsen C
« Reply #132 on: June 29, 2017, 08:57:10 AM »
What speed are they reporting, the growth of the length of the rift or the width?

The way I read the pictures I'd the eastern? (right side) part of the soon-to-be-iceberg is moving away form the shelf with 20+/day, so the rift is widening fast

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #133 on: June 29, 2017, 03:00:32 PM »
They couldn't "see" the growing end of the rift, so the rift growth "had" to be growing width, presumably measured near the rift's 'mouth'.
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Shared Humanity

  • Guest
Re: Rift in Larsen C
« Reply #134 on: June 29, 2017, 04:09:50 PM »
Larsen C is pivoting away from the ice shelf. Still connected on one end, it is opening like a door on a hinge.

magnamentis

  • Guest
Re: Rift in Larsen C
« Reply #135 on: June 29, 2017, 07:59:30 PM »
Larsen C is pivoting away from the ice shelf. Still connected on one end, it is opening like a door on a hinge.

does anyone have insight as to the attributes of shelf ice when it comes to bending and other physical deformation?

what i find quite interesting is that the ice seems to be bendable without breaking to a certain degree which is known, but to what degree that is would be interesting to know.

why? because that way one could predict the angle at which the remaining joint would brake which would mean a possible prediction a few days out only.

what would be interesting about that is that one could perhaps witness the breakup in real time once one knows where and when to watch closely.

solartim27

  • Grease ice
  • Posts: 599
    • View Profile
  • Liked: 42
  • Likes Given: 74
Re: Rift in Larsen C
« Reply #136 on: June 29, 2017, 08:46:38 PM »
Here's how it looks on Sentinel.  Jun 4 - 28
S1A_EW_GRDM_1SSH_20170628T001457_3D5F_S_1.final.jpg

S1A_EW_GRDM_1SSH_20170604T001456_985B_S_1.final.jpg
« Last Edit: June 29, 2017, 09:00:06 PM by solartim27 »
FNORD

iwantatr8

  • New ice
  • Posts: 79
    • View Profile
  • Liked: 21
  • Likes Given: 4
Re: Rift in Larsen C
« Reply #137 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

johnm33

  • Guest
Re: Rift in Larsen C
« Reply #138 on: June 30, 2017, 05:14:08 PM »

crandles

  • Young ice
  • Posts: 3379
    • View Profile
  • Liked: 239
  • Likes Given: 81
Re: Rift in Larsen C
« Reply #139 on: July 05, 2017, 12:28:15 PM »
http://www.bbc.co.uk/news/science-environment-40492957
Giant 'white wanderer' poised to break free

Just 5km left:

Quote
A rift has grown across the edge of the Larsen C Ice Shelf. A thin, 5km-long section of the floating shelf is now all that prevents a 6,600-sq-km berg from drifting away into the Weddell Sea.

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #140 on: July 05, 2017, 07:38:46 PM »
Even Fox News:  Giant 'Delaware-size' iceberg set to break off Antarctica
Quote
Hurry up and read this, before it’s too late.

The Larsen C ice shelf is seconds/minutes/hours/days away from breaking off from Antarctica. When it does — if it hasn’t by the time you’ve finished reading this — it will become one of the largest icebergs on record.

Scientists have been monitoring the crack in the ice shelf for two years, since they first observed that it was growing at a significant rate. As of January, it was 111 miles long and tearing away from the mainland at a rapidly growing rate.
...
Accuracy could be greater, but their heart is in the right place.   ???
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Mozi

  • New ice
  • Posts: 50
    • View Profile
  • Liked: 30
  • Likes Given: 2
Re: Rift in Larsen C
« Reply #141 on: July 05, 2017, 07:49:06 PM »
'The giant berg, the size of Delaware (or 0.31 SWU, Standard Wales Units,)...'

solartim27

  • Grease ice
  • Posts: 599
    • View Profile
  • Liked: 42
  • Likes Given: 74
Re: Rift in Larsen C
« Reply #142 on: July 07, 2017, 08:31:13 PM »
Nice picture in this tweet.
Adrian Luckman (@adrian_luckman) tweeted at 2:53 PM on Thu, Jul 06, 2017:
Close-up of #Sentinel1 Larsen C interferogram - rift branches in all directions. See also: https://t.co/dCZI9Tegtz. Not one clean berg then! https://t.co/sxsCQFZsli
(https://twitter.com/adrian_luckman/status/883081372302266369?s=03)
FNORD

Tor Bejnar

  • Young ice
  • Posts: 4606
    • View Profile
  • Liked: 879
  • Likes Given: 826
Re: Rift in Larsen C
« Reply #143 on: July 08, 2017, 11:13:13 PM »
I cannot see tweets at work, so here are screenshots for others.  See also: Larsen C rift branches as it comes within 5 km of calving.  I'm curious about the cracks shown north of the "2" and "8" in "(2.8 miles)"  Will the collection of soon-to-calf icebergs include that area? (Or are they old and re-sealed/dormant?)  I'm guessing we will have to wait another 6 days for more information (my understanding of the Sentinel-1 satellite schedule over this location).
« Last Edit: July 08, 2017, 11:44:57 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

maga

  • New ice
  • Posts: 28
    • View Profile
  • Liked: 7
  • Likes Given: 0
Re: Rift in Larsen C
« Reply #144 on: July 09, 2017, 12:32:01 PM »
The rifts you mention were probably initiated during the last major calving there in 2005. They probably have a lot to do with pressure from Bawden ice rise and I assume that the calving event will include these rifts as well. Probably not good for the complete northern and central part of the ice shelf...

Shared Humanity

  • Guest
Re: Rift in Larsen C
« Reply #145 on: July 09, 2017, 04:26:27 PM »
I finally found names for the two islands that serve to define the length of the new iceberg. The Bawden Ice Rise to the north and the Gipps Ice rise to the south. These two ice covered islands stabilize the shelf and are worth keeping track of.
« Last Edit: July 09, 2017, 06:48:23 PM by Shared Humanity »

Shared Humanity

  • Guest
Re: Rift in Larsen C
« Reply #146 on: July 09, 2017, 04:31:16 PM »
Nice article.

https://www.nytimes.com/interactive/2017/06/09/climate/antarctica-rift-update.html

Scientists fear that two crucial anchor points will be lost.

According to Dr. Rignot, the stability of the whole ice shelf is threatened.

“You have these two anchors on the side of Larsen C that play a critical role in holding the ice shelf where it is,” he said. “If the shelf is getting thinner, it will be more breakable, and it will lose contact with the ice rises.”

If the shelf front disconnects from the ice rises, a rapid retreat will be triggered.

Ice rises are islands overridden by the ice shelf, allowing them to shoulder more of the weight of the shelf. Scientists have yet to determine the extent of thinning around the Bawden and Gipps ice rises, though Dr. Rignot noted that the Bawden ice rise was much more vulnerable.

“We’re not even sure how it’s hanging on there,” he said. “But if you take away Bawden, the whole shelf will feel it.”

Shared Humanity

  • Guest
Re: Rift in Larsen C
« Reply #147 on: July 09, 2017, 06:52:34 PM »
Given the very fractured nature of the ice shelf near the Gipps ice rise, I would be surprised if, once calved, the Delaware sized ice berg does not quickly fracture into many pieces.

johnm33

  • Guest
Re: Rift in Larsen C
« Reply #148 on: July 09, 2017, 07:22:42 PM »
Good chance it'll break free this week, full moon, low pressure system 954 on nullschool, so extreme high tides. http://www.esr.org/polar_tide_models/Model_AntPen0401_plot_large.png

wili

  • Young ice
  • Posts: 3342
    • View Profile
  • Liked: 602
  • Likes Given: 409
Re: Rift in Larsen C
« Reply #149 on: July 11, 2017, 08:52:52 PM »
New piece on this by rs: https://robertscribbler.com/2017/07/11/antarcticas-4th-largest-ice-shelf-is-about-to-melt-back-to-its-smallest-area-ever-recorded/

Antarctica’s 4th Largest Ice Shelf is About to Melt Back to its Smallest Area Ever Recorded

Quote
... Antarctica could be tipping toward instability far faster than previously imagined.

... the Larsen C ice shelf is about to shatter off a very large 5,800 square mile ice berg even as several smaller ice bergs also appear ready to form. This event, which is now imminent in the coming days, weeks, or at most, months, will break the Larsen C ice shelf back to its smallest area ever recorded even as it marks a period of increased instability and risk of ice shelf loss.

For recent scientific assessments show that Larsen C is lowering in the water — an indication that the shelf is thinning. Furthermore, when the gigantic, Delaware-sized, ice berg and its smaller siblings break off they will take with them two outer sections of a stabilizing compression arch. The compression arch, somewhat like the arch of a flying buttress, helps to balance structural stresses for the ice shelf.

If it were to be compromised in total, according to glacier scientists like Dr. Eric Rignot, Larsen C would soon be adding its name to the list of various ice shelves around the world that have already fallen due to the warming airs and waters produced by human-caused climate change.
"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."