iceberg | Mallemaroking
Mark Brandon • October 15, 2024
I love looking at satellite images of the Antarctic and picking out the icebergs. In the last few years we have had great stories about the giant icebergs A68 in 2020, A76 in 2022 and most recently A23a currently in the Southern Scotia Sea.
At the moment there are two of very large icebergs at the southern end of Antarctic Sound. Here is a map to orientate yourself and show where they are.
A basemap with a MODIS image from 7 October 2024. The yellow box is the location of Antarctic Sound and is expanded on below.
There is a lot in the image above. As well as the Antarctic Peninsula there are clouds, sea ice, and icebergs. Zooming into Antarctic Sound shows the giant icebergs more clearly.
A MODIS satellite image of Antarctic Sound taken on 7 October 2024. Two large icebergs are at the southern end of the Sound. These are A80A and A76C.
And in the radar sensor on Sentinel-1 the icebergs leap out because that sensor “sees” through the clouds.
A Sentinel-1 SAR image from 8 October 2024. Land is coloured blue, the giant icebergs are solid grey, and sea ice and smaller icebergs make up the grey shades colouring the rest of the image.
A80A is 10×9 nautical miles and it calved from the Larsen D Ice Shelf in November 2022. A76C is currently 16×7 nautical miles and was part of iceberg A76 that calved from the Ronne Ice Shelf in May 2021. These are pretty decent sized icebergs: A80A looks to be pinned against Rosamel Island and Andersson Island at the southern end of Antarctic Sound, and A76C grounded against A80A.
Personally I would be surprised if they broke out before the start of the Antarctic season proper, so they could cause some complexities in navigating into the Weddell Sea through Antarctic Sound.
Finally we can’t forget the current monster of them all: A23A at 40×32 nautical miles, and it has been spinning above Pirie Bank north of the South Orkney’s since April 2024. I described it as “the iceberg that just refuses to die” when I spoke to the BBC, and it has been spinning for seven months in pretty much the same location. When it finally breaks free, it’ll head up towards South Georgia and it’s inevitable demise rapid demise.
A MODIS satellite image from 13 October 2024 showing iceberg A23A just north of the South Orkney Islands.
It’s amazing to think that A23A has been in existence since 1986 when it fractured from the Filchner-Ronne Ice Shelf.
The summary? It looks like if you’re going South this season you could see some very big icebergs, and navigation could be complicated in the North West Weddell Sea.
Posted in Science, Uncategorized. Tags: Antarctic Peninsula, Antarctic Sound, antarctica, iceberg, Icebergs on October 15, 2024 by Mark Brandon. Mark Brandon • April 20, 2018
This is a MODIS image from 2004, but it’s too good not to post here.
Iceberg A38 at South Georgia 12 April 2004
I’m giving a talk tonight for the South Georgia Association called Giant Icebergs and South Georgia, so I’m wandering through a lot of these images at the moment.
South Georgia is a small island approximately 190 x 30 km within the Antarctic Circumpolar Current in the South Atlantic. It has a continental shelf that extends more than 50 km from the coast with average depth ~200 m, although there are deeper submarine canyons.
A38 is about 300 Gt in mass, so it’s really significant. The work I was doing on this was picked up in 2010 by the BBC in a story called Giant icebergs head to watery end at island graveyard.
Posted in Science. Tags: A38, iceberg, MODIS, South Georgia on April 20, 2018 by Mark Brandon. Mark Brandon • February 13, 2017
The Metropolitan Museum of Art has made more than a third of a million images both public domain and searchable online. This is one of my current favourites:
An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford and painted in 1871.
An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford, 1871
If you look really closely you can see it is a steam assisted ship.
Detail from: An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford, 1871.
I really like the colours in the sea ice in the foreground. It’s hard not to see that when you are in the sea ice.
Detail from: An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford, 1871.
And let’s not forget the ice bear in the foreground.
Detail from: An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford, 1871.
The caption on the Met page makes clear they were hunting this bear:
In 1861 the marine painter William Bradford made the first of his eight expeditions to the Arctic. This painting, based on photographs and sketches produced during his final trip, in 1869, shows the artist’s steamer, Panther, plying its way through the summer ice along the northern coast of Greenland. Panther was one of numerous vessels engaged in the search for the Northwest Passage between the Atlantic and Pacific Oceans. According to Bradford’s journal, the ship’s crew had decided to hunt the polar bear seen in the foreground, “anxious to possess so fine a skin,” but the bear made a parting glance over its shoulder before heading for the water, managing to escape its pursuers.
But it is art for sure.
There is no way you could get an iceberg with this sort of freeboard close to the shore…
Detail from: An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford, 1871.
And I love the detail of a wrecked ship mast on the left.
Detail from: An Arctic Summer: Boring Through the Pack in Melville Bay by William Bradford, 1871.
There is a long history of romantic artists balancing the struggle of man against the icy wastes. My all time favourite in that category is Landseer’s Man Proposes, God Disposes.
Man Proposes, God Disposes by Edward Landseer 1864.
Thanks Metropolitan museum for putting it online.
Posted in Art, History. Tags: Arctic, Edward Landseer, iceberg, Melville Bay, Metropolitan Museum of Art, polar bear, sea ice, William Bradford, wreck on February 13, 2017 by Mark Brandon. Mark Brandon • January 8, 2017
Project MIDAS publicised on Friday that a huge iceberg is going to calve from the Larsen C Ice Shelf. This was written up a a great story on the BBC news website Huge Antarctic iceberg poised to break away. I understand a little about this stuff so got drawn into the media around it. Here is a BBC News interview on 6 January 2017.
It was great to see Antarctica in the news and it was brilliant to see so many high quality interviews from so many colleagues to different outlets. I may try and collate some of these in the next few days.
Posted in Science. Tags: Antarctic Peninsula, antarctica, BBC News, iceberg, Larsen C, Mark Brandon on January 8, 2017 by Mark Brandon. Mark Brandon • September 27, 2016
On 26th September 2016 the MODIS sensor on The TERRA satellite captured this beautiful image of South Georgia, with Iceberg A66 drifting past.
Iceberg A66 passing South Georgia captured in a MODIS image on the 26 September 2016. The image is available on a KML file on the MODIS Websites.
The iceberg A66 is about 15 km at it’s widest point in this image.
We can do a bit simple maths. Estimate the iceberg has a 200 m thickness and it is triangular in shape with a base of ~4 km.
the volume = 0.5 x 15 km x 4 km x 0.2 km = 6 km3.
So the relatively small A66 contains of 6000 gigtons of water. It’s a lot. But it’s not a lot.
Icebergs get their reference number depending on where they originate from. This one has an identifier “A” which means it came from the sector 0° to 90°W – that’s the Bellingshausen and Weddell Sea region. You can track icebergs like this both visually – like in in the image above – or using something called a Scatterometer. A scatterometer can measure the winds over the ocean, and because the winds change over the ice one can track the icebergs. Prof David Long at Brigham Young University provides an excellent database of Antarctic iceberg data based on that idea (this is their research paper on how they do that).
If we look at the location data from the ASCAT sensor you can see that A66 is at the tip of the Antarctic Peninsula – but this data is only from this year. I will have to dig a little deeper. A job for later.
The track of Iceberg A66 from the BYU database
Once the icebergs reach the edge of the Weddell Sea they get to South Georgia very quickly. I did write about that in a paper in the OU database Physical oceanography in the Scotia Sea during the CCAMLR 2000 survey, austral summer 2000.
And some of these icebergs (although not A66) ground at South Georgia and ultimately can affect the ecosystem. Jon Amos wrote about some work I did at a San Francisco conference in 2010 about that – it’s still available on the BBC website: Giant icebergs head to watery end at island graveyard.
Giant icebergs head to watery end at island graveyard. By Jon Amos
Overall A66 is nothing special, this is not an unusual observation.
It is a beautiful image though.
Posted in Science. Tags: A66, iceberg, South Atlantic, South Georgia, Weddell Sea on September 27, 2016 by Mark Brandon.