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Author Topic: Rift in Larsen C  (Read 57505 times)

Tor Bejnar

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Re: Rift in Larsen C
« Reply #200 on: July 24, 2017, 03:55:34 PM »
I figured out a fallacy in my July 14 post.  The relationship between Iceberg A68 and the remaining Larsen C Ice Shelf is not just a transverse fault, although it looks pretty much like one within the red oval.  The purple arrow pairs are collinear and equally gapped.  One set shows the actual relative movement, the other pair doesn't.  (Whereas the red pair of arrows shows actual relative movement.) (PolarView image from July 22.)

PS: the paper linked by this post may explain my July 14 behavior!
...
link
An excellent paper on how students in Earth and Atmospheric Sciences have difficulty in conceptualizing complex systems.
Students’ Understanding of Complex Dynamic Systems
« Last Edit: July 24, 2017, 04:09:54 PM by Tor Bejnar »
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johnm33

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Re: Rift in Larsen C
« Reply #201 on: July 24, 2017, 07:28:11 PM »
Tor that makes better sense, the tide arrives from the south and given the inertia of this block isn't going to push it north in a hurry, but something has to give so it begins to rotate.

Susan Anderson

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Re: Rift in Larsen C
« Reply #202 on: July 28, 2017, 08:21:44 AM »
Was just over at Earth Observatory where they used parallel parking as a metaphor.
https://earthobservatory.nasa.gov/ (main site because Hudson Bay ice is most recent fwiw)

https://earthobservatory.nasa.gov/IOTD/view.php?id=90627&eocn=home&eoci=iotd_grid
A Fracturing Berg in the Polar Night
“The back-and-forth movement of A-68 looks akin to maneuvering a parallel-parked car out of a tight parking space—like an Austin Powers three-point turn,” said Christopher Shuman, a cryospheric scientist at NASA’s Goddard Space Flight Center and the University of Maryland, Baltimore County.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #203 on: July 28, 2017, 07:54:23 PM »
Nothing exceptional (per my eyes) re A68.  Here's a screen shot from yesterday's PolarView image. (click for larger view; use link for looking at details)
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #204 on: July 31, 2017, 01:56:42 PM »
A68's northern mini-bergs from the July 30 PolarView image.  (The Polar View Antarctica page gives access to recent images.)
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AbruptSLR

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Re: Rift in Larsen C
« Reply #205 on: August 03, 2017, 02:08:44 AM »
With the cracks still spreading in the remaining Larsen-C Ice Shelf, the world (& satellites) will be watching to see how itself integrity holds-up:

Title: “Cracks are still spreading where that massive Antarctic iceberg broke free”

https://www.theverge.com/2017/8/2/16081998/ice-berg-larsen-c-ice-shelf-collapse-antarctica-climate-change

Extract: “Cracks continue to spread on the Antarctic ice shelf where a trillion-ton iceberg roughly the size of Delaware broke free in July, scientists say.”
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

J Cartmill

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« Last Edit: August 06, 2017, 08:06:54 PM by J Cartmill »

Tor Bejnar

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Re: Rift in Larsen C
« Reply #207 on: August 06, 2017, 06:30:40 AM »
August 5 PolarView of the northern corner with the several 'little' icebergs with A68.

Also, fast ice, bergy bits and a gap between fast ice and new ice growing on A68 - near the southern end of A68.
« Last Edit: August 06, 2017, 06:36:41 AM by Tor Bejnar »
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Susan Anderson

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Re: Rift in Larsen C
« Reply #208 on: September 16, 2017, 03:22:32 AM »
Earth Observatory has posted a new picture of iceberg A68:

Daylight Returns to Larsen C
https://earthobservatory.nasa.gov/NaturalHazards/view.php?id=90968&eocn=home&eoci=nh



In August 2017, polar night loosened its grip on the Antarctic Peninsula and daylight began to illuminate the region. That means scientists are getting their first sunlit looks at the massive iceberg that broke away from the Larsen C ice shelf in July. This natural-color image was captured on September 11, 2017, by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.

For about a week before this image was acquired, offshore winds pushed sea ice away from the shelf and out to sea. The remaining thin layer of frazil ice (gray mottled streaks on the dark ocean) does not offer much resistance, letting iceberg A-68A and its companions more easily move about the ocean. Already, scientists have watched the passage widen between A-68A and the front of the ice shelf, and the smaller bits spread out.

NASA Earth Observatory image by Jesse Allen, using data from the Land Atmosphere Near real-time Capability for EOS (LANCE). Caption by Kathryn Hansen.

crandles

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Re: Rift in Larsen C
« Reply #209 on: September 22, 2017, 08:04:41 PM »
Big Antarctic iceberg edges out to sea
http://www.bbc.co.uk/news/science-environment-41366504

But the latest satellite imagery now indicates the near-6,000 sq km block is swinging out into the Weddell Sea.


Susan Anderson

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Re: Rift in Larsen C
« Reply #210 on: October 05, 2017, 05:29:15 AM »
A couple of days back Earth Observatory had new imagery (dated 16 September), but Crandles' is obviously more recent. That thing is moving fast for something so big.



https://earthobservatory.nasa.gov/IOTD/view.php?id=91052&eocn=home&eoci=iotd_grid

bligh8

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Re: Rift in Larsen C
« Reply #211 on: October 06, 2017, 04:13:06 PM »
Modeling tabular icebergs submerged in the ocean

Key Points: A novel-modeling framework is developed to explicitly model large tabular icebergs submerged in the ocean. Tabular icebergs are represented using Lagrangian elements that drift in the ocean, and are held together by numerical bonds Breaking the numerical bonds allows us to model iceberg breakup and calving.                         

Abstract: Large tabular icebergs calved from Antarctic ice shelves have long lifetimes (due to their large size), during which they drift across large distances, altering ambient ocean circulation, bottom-water formation, sea-ice formation, and biological primary productivity in the icebergs’ vicinity. However, despite their importance, the current generation of ocean circulation models usually do not represent large tabular icebergs. In this study, we develop a novel framework to model large tabular icebergs submerged in the ocean. In this framework, tabular icebergs are represented by pressure-exerting Lagrangian elements that drift in the ocean. The elements are held together and interact with each other via bonds. A breaking of these bonds allows the model to emulate calving events (i.e., detachment of a tabular iceberg from an ice shelf) and tabular icebergs breaking up into smaller pieces. Idealized simulations of a calving tabular iceberg, its drift, and its breakup demonstrate capabilities of the developed framework.

http://onlinelibrary.wiley.com/doi/10.1002/2017MS001002/pdf

Tor Bejnar

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Re: Rift in Larsen C
« Reply #212 on: October 25, 2017, 07:37:06 PM »
The Polar View image of A-68A shows the 'large' iceberg between A-68A and the Larsen C migrating northward (toward the left in the image) [or sucked northward into the low pressure 'void'] as the ice island's southern end pivots further into the Weddell Sea.
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Tor Bejnar

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Re: Rift in Larsen C
« Reply #213 on: October 31, 2017, 06:48:33 PM »
The current PolarView  image shows the ice island continuing to move away from the coast (at least at its south end - with North being toward the left in the image) with the 'large' [~10 km] iceberg continuing to be sucked northward.  Of perhaps greater interest is the large area of open water that has opened up to the east (that's 'the top-side' in the image) of A-68A.  Because of the location of the darker and brighter icebergs [each ~4 km long - about 40 km from the left edge of the image] in the previous and current images, it is clear the ice is 'moving out' and not just melting. (Larsen C Ice Shelf is at the 'bottom' of the image.)
« Last Edit: October 31, 2017, 06:59:23 PM by Tor Bejnar »
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oren

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Re: Rift in Larsen C
« Reply #214 on: November 01, 2017, 12:39:45 AM »
Thanks for the updates Tor.

charles_oil

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Re: Rift in Larsen C
« Reply #215 on: November 02, 2017, 02:08:51 AM »


Great pictures from Operation Icebridge of A68


# 3) The western edge of iceberg A68 and the new edge of Larsen C Ice Shelf in the distance:


https://www.facebook.com/NasaOperationIcebridge/photos/pcb.1490399277703754/1490382397705442/?type=3&theater



Do we know how high the broken face is ?

solartim27

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Re: Rift in Larsen C
« Reply #216 on: November 07, 2017, 06:38:27 PM »
Here's a portion of yesterday's Polar View image.  Is the shelf on the right side considered to be part of Larsen C?  It's rift might have reached the edge of the shelf, if not it's real close.  The new rifts on the main part of Larsen C are also expanding.  Going to be an interesting summer.

http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20171107T001502_D6E4_S_1.final.jpg
FNORD

Susan Anderson

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Re: Rift in Larsen C
« Reply #217 on: November 07, 2017, 09:23:17 PM »
Shared this elsewhere but repeating here in case it's of interest: today's look at Nullschool surface temps show many above freezing in the region. Click on spot (greens seem to be the ones) for local temperature:
https://earth.nullschool.net/#current/wind/surface/level/overlay=temp/orthographic=-54.33,-82.99,568

Shared Humanity

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Re: Rift in Larsen C
« Reply #218 on: November 07, 2017, 09:34:30 PM »
Here's a portion of yesterday's Polar View image.  Is the shelf on the right side considered to be part of Larsen C?  It's rift might have reached the edge of the shelf, if not it's real close.  The new rifts on the main part of Larsen C are also expanding.  Going to be an interesting summer.

http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20171107T001502_D6E4_S_1.final.jpg

Yes, that is part of Larsen C. Also, that island where the shelf is pinned is one of two key islands that contribute to the overall stability of the shelf. If the shelf were to recede from this island (Gipps Ice Rise) or the one to the north (Bawden Ice Rise), the entire shelf will be at risk.

Here is an article covering concerns that scientists have about these two pinning points.

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

Shared Humanity

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Re: Rift in Larsen C
« Reply #219 on: November 08, 2017, 03:54:22 PM »
I am fascinated by the dramatic rifting that is visible on Larsen C from the Joerg Peninsula suture zone south. Does this rifting suggest a relatively fragile ice shelf as compared to the northern section of the shelf? If so, the Gipps ice rise may be the Achilles heel of the entire shelf.

Can anyone explain what rifting on a shelf suggests?

Also, the portion of Larsen C that originates from glacier R must be moving slower than the ice on either side, correct?  The rifting/fracturing, on this section of the shelf looks very different. Is this section even more fragile?

We are entering the first melt season since the major calving. Larsen C will be riveting this year. Get your popcorn.
« Last Edit: November 08, 2017, 04:06:04 PM by Shared Humanity »

Shared Humanity

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Re: Rift in Larsen C
« Reply #220 on: November 08, 2017, 04:14:12 PM »
Larsen C is seeing temps significantly above 0C.

Susan Anderson

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Re: Rift in Larsen C
« Reply #221 on: November 08, 2017, 04:30:39 PM »
@SharedHumanity:

Thanks for the terrific visuals on both temps and configuration. Do you know if the "warmth" is abnormal for this time of year?

Shared Humanity

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Re: Rift in Larsen C
« Reply #222 on: November 08, 2017, 04:36:00 PM »
The entire peninsula is experiencing temperatures much higher than normal.

Susan Anderson

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Re: Rift in Larsen C
« Reply #223 on: November 08, 2017, 04:54:57 PM »
Thanks again, also for the reminder to use Climate Reanalyzer. Those visuals are mind boggling. It's tempting to go all extreme on potential melt of the WAIS this year, but I'll try to calm down, remembering what happened to Arctic melt hype so far. Scary monsters.

Shared Humanity

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Re: Rift in Larsen C
« Reply #224 on: November 08, 2017, 05:03:38 PM »
Positive anomalies over the peninsula are expected to weaken but West Antarctica stays warm. Based on expert analysis here provided by others, I don't expect WAIS to contribute significantly to sea levels for many decades.

pileus

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Re: Rift in Larsen C
« Reply #225 on: November 15, 2017, 05:03:20 AM »

solartim27

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Re: Rift in Larsen C
« Reply #226 on: November 16, 2017, 05:23:20 PM »
FNORD

Shared Humanity

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Re: Rift in Larsen C
« Reply #227 on: November 17, 2017, 02:00:39 AM »
Wouldn't surprise me if we had more tabular bergs breaking free this melt season.

Tor Bejnar

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Re: Rift in Larsen C
« Reply #228 on: November 20, 2017, 07:58:28 PM »
Interesting look at the thin new ice between A-68A (top) and the Larsen Shelf (bottom).  As the iceberg moves out, the new ice has to decide if it'll be fast ice (remaining attached to the Larsen Shelf) or stay with the iceberg, or go its own way.  I wonder if sea ice is still growing or if it is in retreat in this area.  Image from PolarView 2017-11-18 via the Polarview website.
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