Antarctic Peninsula | 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 • July 18, 2017
Project MIDAS shows us that the iceberg A68 is about one trillion tonnes.
This is the Antarctic Peninsula and the outline of A68 from the satellite image on 14 July 2017 shown in black. The ice front is from the Bedmap2 data set (so a little out of date), and the bathymetry from the IBCSO data set.
Larsen C Ice shelf on the Antarctic Peninsula and the location and area of iceberg A68. The outline of A68 is derived from a satellite image of the ice shelf 14 July 2017.
There are some astonishingly beautiful processed satellite images of A68 out there such as this one via ESA from Adrian Luckman and the excellent Project MIDAS.
One image I haven’t seen is how good is knowledge of the bathymetry around A68?
The iceberg is going to drift and likely ground quite quickly. (I wrote about this on the conversation a while ago: When an Antarctic iceberg the size of a country breaks away, what happens next?)
In the map below, the shaded colour is the distance of any point on the sea bed to the closest actual depth measurement.
The distance to the nearest good depth measurement around the Antarctic Peninsula.
So the dark blue stripes labelled in the Weddell Sea are actually ship tracks – and the dark colours are good depth data. These measurements will have been made by icebreaker.
Just in front of A68 there is a very large area where no ship has been within ~80 km.
One small note on the size. I digitized the iceberg from a satellite image (a KML File can be downloaded). On twitter today there were satellite images showing fractures already.
New crack on eastern side of Iceberg A68 carves out large chunk of ice, as berg moves further away from #LarsenC Ice Shelf @deimosimaging pic.twitter.com/NagHUSUuH8
— The Antarctic Report (@AntarcticReport) July 18, 2017
But Martin O’Leary of the MIDAS team posted today on twitter that to the untrained eye looks like iceberg, is very likely fast ice (so thick sea ice that is “fast” to A68 – but only a few metres thick.)
Pretty sure this is some fast ice (i.e. sea ice, maybe a few meters thick) detaching from the berg. Looks totally different in SAR imagery https://t.co/XHDGle0gVv
— Martin O’Leary (@mewo2) July 18, 2017
Posted in Science. Tags: A68, Antarctic Peninsula, antarctica, bathymetry, Larsen C, Weddell Sea on July 18, 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 • November 14, 2016
The Prince Gustav Channel was covered by an ice shelf which collapsed in the 1990’s, and for many years it was possible to sail a ship around James Ross Island.
Recently it has been covered with sea ice frozen to the land – we call this fast ice, and it’s usually only a few metres thick of frozen sea water – rather than hundreds of metres thick snow derived ice shelf.
Recent images from the TERRA satellite show that this fast sea ice is finally breaking out.
It’ll soon be possible to circumnavigate James Ross Island once more.
The Prince Gustav Channel early spring Antarctic summer 2016/7 from MODIS satellite imagery on the TERRA satellite.
This map shows the location of the channel.
The Antarctic Peninsula showing the location of the Prince Gustav Channel.
Now it has started I wonder how long it will take to finally clear. Or more fun, I wonder if tour ships will be able to get around the island?
Posted in Science. Tags: Antarctic Peninsula, fast ice, MODIS, Prince Gustav Channel, sea ice on November 14, 2016 by Mark Brandon. Mark Brandon • October 6, 2016
I’ve been watching the open water down the eastern side of the Antarctic Peninsula. I said the cause of that was most likely strong westerly winds.
If you look at the sea ice concentration on the western Antarctic Peninsula you can see the effect of these westerly winds.
Towards the end of September 2016 the ice edge is compacted as the sea ice is pushed against the Peninsula.
The Antarctic Peninsula sea ice 24 August to 5 October 2016. Data from DMSP SSMI
The westerly winds (from bottom left to top right) compress the sea ice against the land (left hand side of the Antarctic Peninsula). This also creates open water on the eastern (right hand side ) of the Peninsula as the sea ice is pushed away from the land.
You can see the very sharp ice edge on the west, and the open open water in the MODIS satellite imagery.
MODIS image of the Antarctic Peninsula 5 October 2016 from the Aqua satellite.
The sea ice concentration anomaly for September 2016 shows that on both sides of the Antarctic Peninsula the westerly winds have reduced the amount of ice we would expect to observe by up to ~40%. On the west side because the sea ice is compressed, on the east side because the sea ice is being pushed away from the land.
Antarctic sea ice concentration anomaly for Sep 2016. Yellow rectangle approx area of images above. Image from NSIDC
This is just late winter weather.
There are a lot of Antarctic research stations on the west of the Antarctic Peninsula, including Rothera, the largest British Base. If the winds maintain the westerly direction then I can imagine it could be slow to resupply the base this season. There is time for it to change. According to the published schedule the ship is not due to arrive until 27 November 2016.
A slow resupply is not uncommon and I have been on at least one unsuccessful resupply voyage in my career. I took the picture below on 11 December 2004 under similar conditions.
RRS James Clark Ross making very slow progress in compressed sea ice in Marguerite Bay, the Western Antarctic Peninsula 11 December 2004. Posted in Science. Tags: Antarctic Peninsula, James Clark Ross, Marguerite Bay, Rothera, satellite, Science, sea ice, Weddell Sea on October 6, 2016 by Mark Brandon. Mark Brandon • October 3, 2016
I noticed in a blog post last week that there was a finger of open water extending down the Western Weddell Sea. I’ve carried on watching this open water in the MODIS satellite data. Whilst it’s been opening and closing, there is a lot of open water. It’s clearly a major sea ice generating factory at the moment.
MODIS image of the Western Weddell Sea 30 September 2016. The Open Water is clear.
The open water is clear in the lower resolution passive microwave sea ice data too.
The sea ice extent along the Antarctic Peninsula 2 October 2016. Data from DMSP SSMI
If you look at some model output there are air temperatures above this open water of between -10° to about -25°C.
Surface temperature at 2m from NCEP output. 3 October 2016. From Climate Reanalyzer.org
What is really good is if you look at the temperature anomaly (i.e. the departure from the average with a 1979-2000 baseline), it is very warm over the Weddell Sea.
The temperature departure from average for NCEP output 3 October 2016. Image from climateReanalyzer.org.
I think the reason it is warmer is because the Weddell Sea pack ice is looser this year. So (as you can see in the picture above) there is lots of open water. The atmosphere is being warmed by the ocean as the sea ice is being generated.
Another pointer to the pack being looser this year is that in August 2016 in the Eastern Weddell Sea there was a rare sighting of the Weddell Polynya.
The Weddell Polynya as observed on 14 August 2016 in passive satellite data. It is a polynya with its own wikipedia page.
I think the Weddell Sea pack ice is more mobile this winter. This is also telling us something about the difference between sea ice extent and sea ice thickness. The sea ice extent is large and easy to measure in the Antarctic – but we don’t know how thick it is.
Posted in Science. Tags: Antarctic, Antarctic Peninsula, MODIS, polynya, satellite, Science, sea ice, Weddell Sea on October 3, 2016 by Mark Brandon. Mark Brandon • September 26, 2016
The low sea ice extent I noticed in my previous blog post about Antarctic Sound has extended southwards along the east side of the Antarctic Peninsula.
The sea ice extent along the Antarctic Peninsula 24 September 2016. Data from DMSP SSMIS
The open water that shows up as black in the image above extends to at least as far south as the Antarctic Circle (66° 33′S). Open water along this part of the Antarctic Peninsula is unusual at any time of the year let alone the height of winter. The image below is from the National Snow and Ice Data Centre. It shows sea ice extent >15% with an outline of the typical extent for that day based on a 30-year (1981-2010) median (orange line).
NSIDC Antarctic sea ice extent 24 September 2016 with the median extent (1981-2010) for this day.
You can see how unusual this observation is, and I wrote a general post Antarctic Sea Ice Extent a while ago.
The open water is also very clear in the MODIS imagery as the black wedge between the Antarctic Peninsula, and the sea ice of the Weddell Sea.
The MODIS imagery for the Antarctic Peninsula 25 September 2016.
In my previous post I pointed at weather systems as likely being responsible. Now to me it looks like a large system is pushing the whole Weddell Sea sea ice to the east and away from Antarctic Peninsula.
There is always some open water in the pack ice at any time of the year, but it’s clear that their is a pathway south right now. I imagine it will close soon and wouldn’t be keen to be on a ship in that open water heading south.
What is interesting is the heat transfer from the ocean to the atmosphere that far south at this time of the year will be huge. This is what I wrote about that heat loss for the Arctic.
Posted in Science. Tags: Antarctic Peninsula, MODIS, open water, satellite, sea ice, Weddell Sea on September 26, 2016 by Mark Brandon. Mark Brandon • September 16, 2016
Just noticed this on the MODIS sensor on the TERRA satellite image from 10 September 2016. (Tile Antarctica_rc05c01 if you are interested in that sort of thing)
Antarctic Sound on the tip of the Antarctic Peninsula 10 Sept 2016
The Antarctic sea ice ice extent map for 10 September 2016 shows an interesting and large low concentration right at the tip of the Antarctic Peninsula
The sea ice extent around Antarctic 10 September 2016. Yellow box is roughly where the MODIS image is, and Antarctic Sound is labelled. Data from DMSP SMMI
So why the missing sea ice at the top of the Peninsula? It could be a storm, or could be heat from the ocean keeping the area ice free. I’ll have a look at the data when I’ve time, but for now I would bet on the ocean.
Interestingly historically it has been a bit of a tough place. Otto Nordenskjöld navigated the sound in December 1902 on the Swedish Antarctic Expedition before their ship, the Antarctic was crushed and lost. They were stranded for two years…
Posted in Science. Tags: Antarctic, Antarctic Peninsula, Antarctic Sound, Joinville Island, MODIS, satellite, sea ice, Swedish Antarctic Expedition, Trinity Peninsula on September 16, 2016 by Mark Brandon. Mark Brandon • August 29, 2014
In the old days Antarctica wasn’t mapped and measured by satellites like it is now. In the past it was all about exploration. Scientists were dropped at bases by ship, and then left for at least a year – sometimes two. Very occasionally more.
When winter comes the sea ice freezes up and the area of sea ice is vast. But after the winter, spring brings long days of light, and that meant travel by dog sled was possible over the ice!
To make the sled journeys more efficient food caches were left along the coast the previous summer perhaps by the same ship that left them. Then the scientists could journey easily over the frozen sea ice to the food cache, and then work inland in their area of operations.
Which brings me to these pictures. This is a food cache left by a ship (I think) in 1962 for a science team setting out from Hope Bay.
Hope Bay Food Dump
Antarctic Chocolate and meat
In Antarctica Marmite can come in tubes
Butter and meat
A tin of biscuits in an Antarctic Food Cache
Oxtail soup and a meat bar
A pile of wooden sledge boxes that contain all human needs: chocolate, biscuits, marmite, meat and soup. What more could you want?
…continue reading →
Posted in History, Science. Tags: Antarctic Peninsula, Food, history, Hope Bay, polar on August 29, 2014 by Mark Brandon. Mark Brandon • February 4, 2014
In a previous post I showed the temperature cycle on the Antarctic Peninsula, and pointed out that the monthly mean atmospheric temperatures show that it is actually surprisingly moderate. Whether you consider the temperature cycle moderate or not, the cold temperatures and strong winds drive an amazing amount of seasonal sea ice production.
This plot shows the average seasonal cycle of Antarctic sea ice extent against date.
Seasonal cycle of Antarctic sea ice extent
The daily average extent is calculated from the satellite record from 1981-2010, and the grey shading either side of the line is the standard deviation.
Here are three obvious things to pick out of this plot.
- Antarctic Sea Ice extent varies a lot: From 2.9×106 km2 in February to 18.6 x106 km2 in September. This is a range of 15.7 x106 km2.
- The seasonal cycle is not symmetrical: There is a slow growth followed by a relatively rapid decay.
To really get an idea of what this asymmetric growth / decay pattern looks like watch the following you tube clip a few times. (The data for the movie is from the AMSR-E Satellite and it is from Climate Central.
So slow growth, and then rapid retreat. Ice tends to advance away from the continent, but as it retreats it can melt first within south of what you would consider the ice edge.
How the Antarctic sea ice extent is changing is for a future post, but it is currently increasing. There are significant regional changes over the duration of our satellite record. For a couple of good accesible comments on the trends in Antarctic sea extent you could read Professor John Turner in the Guardian, or Tamino on the Antarctic Sea Ice increase.
Data source
The average sea ice extent is part of the National Snow and Ice Data Center (NSIDC) Sea Ice Index.
Fetterer, F., K. Knowles, W. Meier, and M. Savoie. 2002, updated daily. Sea Ice Index. Daily Sea Ice Extent Climatology. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5QJ7F7W.
The actual file I used is downloadable from this FTP location.
Posted in Science. Tags: Antarctic Peninsula, antarctica, sea ice on February 4, 2014 by Mark Brandon.