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Author Topic: Antarctic Icebergs  (Read 48803 times)

FredBear

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Re: Antarctic Icebergs
« Reply #400 on: January 16, 2021, 01:00:57 AM »
A68A has been moving (not grounded) up to 15th January but clouds obscure how much it is breaking up (on Worldview). Lots of bits falling away from A68E since it formed.

Stephan

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Re: Antarctic Icebergs
« Reply #401 on: January 21, 2021, 07:19:08 PM »
A short inspection of B-22 and its surroundings.
B-22 is slowly moving NNW-wards (green arrow). Thus it widens the sea ice area south of it.
The currents (yellow arrow) in that sea are directed into NW. In the last weeks some larger icebergs have moved to the bottleneck (orange circle). Therefore this gate is now almost closed because these icebergs are grounded in shallow seas.
In this area already are grounded icebergs since 1-2 years (black "x"). The new icebergs are marked with a red "x".
This new barrier will help to slow down the flush out of the sea ice and icebergs which may stabilise the edge of the fast ice that protects Crosson and Thwaites ice shelves.

The red box (upper picture) shows the area of interest (lower picture).

See attached picture. May need a click to enlarge.
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FredBear

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Re: Antarctic Icebergs
« Reply #402 on: January 28, 2021, 11:16:09 PM »

interstitial

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Re: Antarctic Icebergs
« Reply #403 on: January 29, 2021, 07:29:56 AM »
As it gets farther north in warmer waters and the hottest part of summer work on it A68 should be mostly gone by the end of march. IMO

gerontocrat

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Re: Antarctic Icebergs
« Reply #404 on: January 29, 2021, 11:54:57 AM »
As it gets farther north in warmer waters and the hottest part of summer work on it A68 should be mostly gone by the end of march. IMO
https://www.bbc.co.uk/news/science-environment-55843384
Quote
A major question now is whether the scientific expedition that was aiming to study the iceberg will have anything left to observe by the time it arrives on site.

Researchers will soon board the British Royal Research Ship James Cook in the Falkland Islands and sail east towards South Georgia.

They have other, unrelated investigations to pursue as well, but they were hoping to place some autonomous vehicles around A68a to learn more about its impacts on the environment.

Their study subject has got considerably smaller since the expedition was announced in mid-December.
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FredBear

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Re: Antarctic Icebergs
« Reply #405 on: January 30, 2021, 04:31:15 PM »
A68 bits surround South Georgia (cut from Worldview, 30/01/2021) - Top= A68E, Middle= A68D, Bottom= A68A in bits:-

paolo

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Re: Antarctic Icebergs
« Reply #406 on: February 05, 2021, 02:55:56 PM »
I found on the ESA website this photo of 01/02, the disgregation of A68A was already well advanced ...

Click to enlarge

grixm

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Re: Antarctic Icebergs
« Reply #407 on: February 06, 2021, 07:44:06 PM »
A23A in the Weddell sea, which has been floating quite freely this season, appears to have been grounded again. It hasn't budged in the last 4-5 days.

FredBear

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Re: Antarctic Icebergs
« Reply #408 on: February 10, 2021, 02:36:11 PM »

A23A is still grounded (top NE corner has only moved from Lng -40.52 Lat -76.06 [2000 Mar 05] to Lng -39.86 Lat -75.66 [2018 Dec 05] over 18.75 years!). It has had a tendency block ice flow to the south and east of the Weddell Sea over this time. The Brunt ice shelf to the NE accumulates 1.5m snow/year (which has been burying the BAS Halley stations), so it might be possible that A23A is growing in thickness rather than melting? This iceberg could affect any break-up of the Brunt ice shelf & where the resulting icebergs move, as the natural flow is to the south and west.

A23A has been "dancing a jig" in the last year, twisting and partly turning with no constant centre of rotation, so it may be "rubbing the bottom" but there is no fixed grounding point. The net distances traveled in the last year are approximately:-

NW tip      61.3 km
SW tip      36.6 km
NE tip       41.7 km
SE tip       15.2 km
The NW tip has been twisting from NW -> W -> SW and back so has actually covered a considerably larger distance.

In most of the 2000's A23A has been surrounded by somewhat dispersed ice floes in February except in 2001 when cloud streets show the surrounding sea cleared by the wind and a peninsular built up behind the iceberg.

A23A is not leaving the Weddell Sea anytime soon in my opinion although ice formation to the south may help move it north during the southern winter now that it is not solidly grounded.

(Observations based on Worldview)

FredBear

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Re: Antarctic Icebergs
« Reply #409 on: February 11, 2021, 04:26:58 PM »
Worldview snapshot of the remains of A68, mostly grinning through the clouds round South Georgia.
The bits of A68A form an arc from bottom right round the island towards the A68E debris at the top left.
A68D is too small to identify amongst the debris - if it has not broken up already?

FredBear

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Re: Antarctic Icebergs
« Reply #410 on: February 17, 2021, 04:12:15 AM »
British Antarctic Survey have announced "Giant iceberg mission begins" (2nd February 2021) with details of the named parts of A68A after it broke up recently:-

https://www.bas.ac.uk/media-post/giant-iceberg-mission

kassy

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Re: Antarctic Icebergs
« Reply #411 on: February 17, 2021, 11:13:06 AM »
Some general ice berg research:

How icebergs really melt -- and what this could mean for climate change

Current models wrongly assume icebergs melt uniformly in warming oceans

Icebergs are melting faster than current models describe, according to a new study by mathematicians at the University of Sydney. The researchers have proposed a new model to more accurately represent the melt speed of icebergs into oceans.

Their results, published in Physical Review Fluids, have implications for oceanographers and climate scientists.

Lead author and PhD student Eric Hester said: "While icebergs are only one part of the global climate system, our improved model provides us with a dial that we can tune to better capture the reality of Earth's changing climate."

Current models, which are incorporated into the methodology used by the Intergovernmental Panel on Climate Change, assume that icebergs melt uniformly in ocean currents. However, Mr Hester and colleagues have shown that icebergs do not melt uniformly and melt at different speeds depending on their shape.

"About 70 percent of the world's freshwater is in the polar ice sheets and we know climate change is causing these ice sheets to shrink," said Mr Hester, a doctoral student in the School of Mathematics & Statistics.

"Some of this ice loss is direct from the ice sheets, but about half of the overall ice loss from Greenland and Antarctica happens when icebergs melt in the ocean, so understanding this process is important.

...

Co-author Dr Geoffrey Vasil from the University of Sydney said: "Previous work incorporating icebergs in climate simulations used very simple melting models. We wanted to see how accurate those were and whether we could improve on them."

Mr Hester said their models -- confirmed in experiment -- and the observations of oceanographers show that the sides of icebergs melt about twice as fast as their base. For icebergs that are moving in the ocean, melting at the front can be three or four times faster than what the old models predicted.

"The old models assumed that stationary icebergs didn't melt at all, whereas our experiments show melting of about a millimetre every minute," Mr Hester said.

"In icebergs moving in oceans, the melting on the base can be up to 30 percent faster than in old models."

The research shows that iceberg shape is important. Given that the sides melt faster, wide icebergs melt more slowly but smaller, narrower icebergs melt faster.

"Our paper proposes a very simple model that accounts for iceberg shape, as a prototype for an improved model of iceberg melting," Dr Vasil said.

...

https://www.sciencedaily.com/releases/2021/02/210216133415.htm
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