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Shirase Glacier / Lützow-Holm Bay / Riiser-Larsen Peninsula

Started by Often Distant, August 29, 2023, 08:27:51 AM

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Often Distant

East Queen/Dronning Maud Land
Indian ocean sector

This is an unstable segment of East Antarctica set to appear a lot different in years to come. Located 70°S/ 38°E, Shirase is a mid size glacier near 10km wide occupying an extended deep depression over 200km. It drains a catchment area of 165,000 km2 where ice mass has gained through snowfall in recent decades. Shirase flows at velocity exceeding 2km per year, near 6m per day. One of the fastest flows on the continent. Depths below the floating tongue exceed 1km with warm saline water intrusion from the north. Bottom melt rates may exceed 10m per year. Icebergs can be well beyond 500m thick. Outflow is highly constrained by bathymetry, with a long fracturing frontal tongue prone to colliding into island mass. Relentless force keeps warping through. Fast sea ice generally embraces the bay. Early sea ice break up can be extremely dramatic. Multi-year fast ice can be multiple metres thick. Today it is mostly young.

The tongue is extending roughly about as far north as it has in over 3 decades. The bay was clear of the tongue back to the calving front in Havsbotn Bay in 1988. Sea ice disintegrated in 1997 and 1998 to bring the tongue back down. Sea ice largely broke up a couple of years in the mid 00's and mid 10's without drawing out most of the tongue. In recent years late sea ice break up has tended to be brought to a halt through the onset of freeze. The next time the tongue clears out, the neighbouring gigantic Kaya tongue may be joining a ride alongside much of what remains of the gigantic old tongues of the Riiser-Larsen Peninsula. Large ice mass loss is on the cards, and cards are falling.

The first gif is of EO Browser imagery from 2015 to 2023 displaying the pulling away motion of the peninsula ice intensifying. It seems to be losing its grip. Shallow bathymetry highly constrains ice bergs at the northern tip, largely fencing them in for 40km. They need to go around it or through it like pepper through a grinder. The second gif of Nasa Worldview imagery from 2000 to 2023 focuses on the progression of the shirase tongue extension and sea ice characteristics.
On the 1974 annotated image, the tip of Kaya appears pointing toward the tip of the Shirase tongue and Padda Island. In images from 1989, Kaya appears close against Botnneset Peninsula/Prince Harald Land/ Austhovde rocks. In 2023 it is tending north and it no longer seems to move very slow. 100 years worth of tongue could soon pull away.

1989 peninsula images are flipped horizontal for orientation, and are lifted from this study:
https://www.cambridge.org/core/journals/annals-of-glaciology/article/antarctic-glaciertongue-velocities-from-landsat-images-first-results/98ADAE986007FF2C65FB119A607216EC
1973 and 1988 comparison taken from this article:
https://www.sciencedirect.com/science/article/pii/S1873965210000381
1990/1997/2007 comparison taken from here:
https://www.eorc.jaxa.jp/en/earthview/2007/tp071017.html

1974 annoted landsat image is taken from this useful historical resource:
"Satellite Image Atlas of Glaciers of the World ANTARCTICA":
https://pubs.usgs.gov/pp/p1386b/p1386b.pdf
The atlas was more interested in inland meteorite study location and overlooked the peninsula.

Kaya looks understudied. What is known about it? What did it look like?

The sea ice is breaking up right now, before the end of winter. Developing situation.
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Often Distant

#1
It is under cloud. Winds have been high. This is the sea ice a couple of days ago.

Can it refreeze? If it does, how long can it hold?
The answers are flowing in the seas.
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Often Distant

Shirase. One to watch through the dark. A rare clear out event is not far off. Could yet be the season for it. High winds competing with refreeze. A "small" iceberg breaks away from the front of the "tongue".

Attached is a 40 day worldview animation to focus on the ice situation in the bay and a more detailed image comparison of glacial ice. Fast sea ice rarely breaks up in a year.
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Often Distant

Watch this space. With fast sea ice further breaking up, so are Shirase ice bergs, with significant calving occurring within the tongue conglomerate, which will be speeding up toward eventual quick clearing out a quarter century of glacial extension. Pressure is breaking. When the gates open, satellites may miss most of the drama whilst they re-orbit. The technology becomes slower than the glacier. This will be an active freeze season worthy of close monitoring. Expect every new image through to show something of note. I will not provide frequent updates and will not be observing closely. Please do so if you can as it will largely go unseen, and is huge and interesting. Satellite imagery pre-2000 for comparison is scarce, as if there were some sort of millennium bug or digital data glitch rendering an ailing failing species infants in the dark to information. The previous Shirase clearance event occurred prior to the earliest dates captured by Worldview imagery. This event may occur under night vision malfunction.

Sea ice should struggle to gain a fastened hold for extended duration throughout the season. High winds will effect activity. The mass of melange build up against the extending peninsula make it less likely the thick Shirase icebergs will be constrained to such shallow confines of the bay. They may be swept out on a deep trough expressway, well on their way to the Weddell by sunrise.
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Espen

Shirase Glacier 2017 - 2024:

Please click on image to enlarge and animate!

Have a ice day!

Often Distant

The first gif shows sea ice breaking up in Lützow-Holm Bay over recent days on worldview. High waves and warm temps have been encroaching.
The second gif is a 10 month Sentinel-2.comparison of Shirase Glacier. Compressed bergs have been crumbling down within. Separation of frontal segment imminent. Should be an eventful season.
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Often Distant

A few closer details down the tongue conglomerate. The first gif compares January 6 2025 with November 7 2024. The next 3 also include January 2 2024.
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Often Distant

With the sea ice in rapid collapse, Icebergs are now breaking away from nearby Skellen and Telen Glaciers, which is disconnecting multiyear fast ice east of Shirase Glacier. A lot is about to happen.

On the 16th, Shirase Glacier looks to have received roughly 10 hours of light rain. I am not sure as to how rare such occurrence is. Temperatures have reached multiple degrees celcius above zero. Fridge temp.
Climate change is exploited and exacerbated to keep nocuous nuisance scooter scams obstructing streets in cities with microwheeled and moped street spam, causing climate change skepticism. Motor vehicles carelessly declared child toys in NZ. Terminable batteries to explode toxic emissions on expiry.