This is a MODIS image from 2004, but it's too good not to post here.
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.
I was looking this morning at the recent Sentinel-1 imagery on Polarview, this is an image of A68 captured on 11 February 2018. It's big - about 5,200 km2.
I labelled some features in the image: the iceberg and the ice shelf are the relatively solid grey colour. The blue overlay is where land and the ice shelf roughly were (it's called a land mask).
One thing you can see is the speckled grey colour which covers the top right hand side.
This speckled grey is sea ice.
It's a relatively thin cover of a typically 1-3 m thick.
If you map the current sea ice distribution, and the location of iceberg A68 you can see how much sea ice they are going to have to sail through to reach the region.
There is a lot of high concentration sea ice between the ice edge and the iceberg that the ship will have to traverse. RRS James Clark Ross is a very capable ship, and she will be able to make way through the ice.
The issue is this can take a lot of time.
And time whilst ice breaking is fuel.
In open water a research ship can cover ~22 km per hour, in sea ice if you are breaking ice then maybe 5 km per hour would be good, and you probably wouldn't break ice 24 hours per day.
They have 3 weeks.
Plus if you sail 400 km in the ice, unfavourable winds can easily compress the sea ice and trap a ship. It's happened before, and in the modern era even capable ships get can get held up.
The satellite I used to make the image doesn't do so well in coastal regions, so given some favourable winds there could be a nice channel for them. I am going to be watching the visible satellite imagery for that.
It's easy to make pronouncements from 14,000 km away, but really the people on the ground will work it out.
Whatever happens I know that the researchers on board will do some great research. Plus I would be surprised if A68 moves too far from the region in the next year.
Being interested in the Weddell Polynya I plotted some time series data from 1 September 2017 to 23 November 2017. On the left-hand panel, you can see the see the sea ice concentration, on the right-hand panel, the anomaly of the concentration each day compared with a mean from 1989-93.
The Weddell Polynya is the low concentration region at approximately 12:00 in the movies below.
You can see the Weddell Polynya isn’t stationary.
You can also see the sea ice is still relatively low compared to the historic record. We should expect this after the extreme low sea ice from ~October 2016 onward.
I will write some more about this next week but for interest here is the Antarctic sea ice extent anomaly for 2017.
Antarctic sea ice extent remains low compared with the 1981-2010 median extent. This image shows the mean from 1989-93, the extent on 20 November 2017 and the difference between the two. Red colours imply that there is a decreased sea ice extent compared with the mean.
Last month, SOCCOM scientists were astonished to discover that a float in the Weddell Sea had surfaced inside the polynya, making contact with satellites in the dead of winter. Its new ocean measurements, transmitted when it surfaced, are being analyzed as part of a study in preparation on Weddell Sea polynyas. With these new observations comes the possibility that the polynya’s secrets may finally be revealed.
We should expect some exciting research articles soon.
Sea ice extent currently ~1.2 million km2 low
The overall sea ice extent is currently ~1.2 million km2 below 1981-2010 median extent. This sounds a lot.
But at this time of the year the Antarctic sea ice is about to dramatically fall as spring develops. If spring "arrives" early then the extent will - as we see, be relatively low.
Whilst the full on development and opening of the Weddell / Maud Rise Polynya is unusual, if you compare the sea ice on 18 November 2017 with the extent from the same day on 1989-1995 it is clear that the extent is often lower over Maud Rise, at this time.
I will keep watching the sea ice as the summer season develops
** UPDATED 20th November 2017 replacing the first figure from 17 November to 20 November.
As daylight has returned to Antarctica it is straightforward to pick out polynya forming on the edge of the Antarctic continent.
This one by the Stange Ice Shelf and Rydberg Peninsula caught my eye. It is a latent heat polynya formed as the winds push the sea ice away from the land to reveal the ocean that appears black beneath.
The wispy trails of grey which appear in the black are new sea ice forming as frazil ice.
This is the location of the peninsula.
I visited that area in 2007 and took this picture. You can a thin skim of young nilas ice in front of the ice shelf, and sea smoke too.
This incredible series has been made by the BBC Natural History Unit with the Open University as co-producers. It has seven stunning episodes and will be broadcast in the UK at the end of October 2017.
Yesterday was the World Royal Premiere at the BFI Imax with Sir David Attenborough, Prince William, Radiohead, Hans Zimmer, and a team of BBC program makers that is too long for this post.
The prequel above was released after the premiere.
Episode one one the big Imax screen was stunning, and just after there was a Q&A led by Liz Bonnin with some of the key people:
Sir David Attenborough, James Honeyborne, Orla Doherty, Mark Brownlow and Hans Zimmer.
It's been a brilliant experience to work with so many incredible film makers - many of whom also have PhDs to go with their artistic and technical talent. You often hear about how the media want to tell their own story - but in my experience the NHU just want it to be the best - and, of course, correct.
I'm proud to have been a small cog in the mighty and incredible machine that made this series, and I'm looking forward to seeing how it is received.
It has been an amazing experience to be one of four marine scientists at The Open University to have contributed to the series. As well as helping the production team we've been developing interactive learning materials and a poster for the general public and our students that will also be released at the end of October.
I hope the film makers get the awards I think they deserve for making such a powerful work.
The Weddell Sea polynya is an area of open water that sometimes appears in the Weddell Sea over a relatively shallow region called Maud Rise.
In the latest satellite imagery from the DMSP satellite you can see the lower concentration sea ice as the darker blue colour. If you look at the MODIS imagery for the same date you can clear see black which indicates open water in the pack ice.
This movie shows the Antarctic sea ice extent from 1 Feb to 25 July 2017. The data come from the DMSP SMMI sensor, and it shows the expansion of the sea ice as winter progresses.
For me the stand out feature is how late the sea ice expands in the Bellingshausen Sea. I think this is a feature of the super low sea ice last year, and the amount of time it took to lose the extra heat absorbed by the ocean.
The NSDIC data set shows the sea ice is lower than we've seen before by satellite.
Currently the Antarctic sea ice extent is ~450 thousand km2 below 1981-2010 median.