Watching the sea ice extent this summer in Antarctica has been a bit surprising. The Antarctic sea ice extent has been tracking at record lows virtually the whole austral summer. We are very close now to the expected sea ice minimum, and this is where we are:
On the left is the sea ice extent from the DMSP satellite 12 February 2017, and on the right the difference between the mean sea ice extent on 12 Feb over the period 1989-93 and 12 Feb 2017. I chose this time period as the cycle has been generally quite stable from year to year.
The current sea ice extent is:
It's clear the sea ice over the summer 2016-17 is showing historic lows. But it's also clear from the sea ice extent above that there is little sea ice left to melt out before the summer turns. Where the sea ice remains - mainly in the Weddell Sea and along the coast of Wilkes Land it is clearly densely packed. If the winds change and the remaining sea ice is decompressed then the extent may fall some more.
This is an animation of the Antarctic sea ice extent from 1 January 2017 to 12 February 2017:
And finally the difference between the mean sea ice extent by day for the 5-year period 1989-1993 minus the concentration from 1 Jan to 12 Feb 2017. Blue shades imply an increased sea ice extent compared with a 5-year mean, and reds imply a decreased sea ice extent.
If you look really closely you can see it is a steam assisted ship.
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.
And let's not forget the ice bear in the foreground.
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...
And I love the detail of a wrecked ship mast on the left.
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.
The sea ice around Antarctic is currently still at an historic low. As usual I think it is good to look at a geographic perspective on the sea ice distribution. This is the sea ice concentration 22 January 2017 compared with the 1989-1993 mean on the 22 January.
RED shades = less sea ice than the 1989-93 mean on 22 January.
BLUE shades = more sea ice than the 1989-93 mean on 22 January.
The Amundsen Sea has very low sea ice
Probably for me the most striking feature is the extremely low sea ice concentration from Pine Island Bay through to the Ronne Ice Shelf - this is the Amundsen Sea. We are not going to see much more retreat of of the sea ice in this sector as it has already melted. I think it will stay open water until the freeze up begins some around the end of February. It would have been a great year to do ship based oceanography along that coast. I wonder if their could be an impact on ice shelf melt here. It is possible but as you can see from this article - it is water away from the surface and a few hundred metres deep that is in contact with the glacial ice in the Amundsen Sea Embayment, Overall this has to be a result of the recent El Nino, and is a follow on from the polynya events we saw hear in the late winter.
The Bellingshausen Sea has very relatively high sea ice
In contrast you can see it would not be a good year to be working in the Bellingshausen Sea.
The Weddell Sea ice is at this stage in the summer is compressed against the Antarctic Peninsula. This means that there is heavier sea ice to the close to the Peninsula, and much lower sea ice than expected in the rest of the Weddell Sea. If you look at the MODIS Terra Image you can pick out a very sharp sea ice edge.
Shackleton would have been in trouble this summer if he was heading to Elephant Island.
Towards the annual Antarctic sea ice extent minimum.
We expect the sea ice to reach a minimum towards the end of February. Clearly there are places where there is no more sea ice to melt. Where sea ice is present, it is all down to winds over the next month. If they change and move the pack towards open water then - just as we have seen in the Arctic, the concentration could fall much lower. If the winds continue as they have then we could expect the extent fall to slowly as the seasonal melt continues.
Overall it is still to be likely a record breaking year in the Antarctic sea ice extent record.
Sea ice continues to be very low in the Arctic this winter. A geographical perspective always helps so here is the status of the sea ice concentration 18 January 2017 compared with the 1989-1993 mean on the 18 January.
RED shades = less sea ice than the 1989-93 mean on 18 January.
BLUE shades = more sea ice than the 1989-93 mean on 18 January.
A few interesting areas that caught my eye:
The first highlight region is the Northern Barents Sea. Sea ice has been very low here all winter, and this situation continues. Because the sea ice has been very late, the polar bears on Svalbard will be impacted, and it has been an issue in Longyearbyen....
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.
The ice edges have retreated compared with 1989 - but as I wrote about in Record Low Arctic Sea Ice Extent we still have the very low sea ice concentration in the Barents Sea. There is also still a very low concentration region north of the Bering Strait but the the Chukchi Sea and Hudson Bay have mostly frozen over.
I was asked “what is an easy way to get a satellite image into Google Earth?”. Once I explained how I do it I thought it may be of interest to others. NASA have provided a really excellent web interface to some of their visual data called Worldview.
The Worldview description puts into perspective how good it is.
The Worldview tool from NASA's EOSDIS provides the capability to interactively browse global, full-resolution satellite imagery and then download the underlying data. Most of the 200+ available products are updated within three hours of observation, essentially showing the entire Earth as it looks "right now"
More than 200 data products within three hours…
Open worldview and this is the screen you are greeted with. It is easy to use. The key regions are the projection / copy / link tool in the yellow square on the right, the date control in the yellow box on the bottom of the browser screen and the layers control in the yellow box on the left.
I do recommend following the tour to find your way around the data sets.
If you click the layers button (red on the left) this is just a part of the choice of real time data you can easily access.
So you select the data you want to see, and then you can zoom in and easily download areas of interest. For some reason I always seem to find my way at this view
This movie I made shows how you can get imagery from Worldview easily into Google Earth.
I hope you find this useful. It's easy to spend a lot of time looking at this data.
Navigation charts in Antarctica may not be as good as you think. It makes sailing in those regions a little more exciting than you could hope. Here is an example.
Five miles wrong... What does that mean?
Here is London with a 5 mile radius circle drawn on it.
If you sailed your ship to a position - say the edge of Rothschild Island, you would not know the exact location of that coast to within the radius of that circle.
Just get your head around that. In this age of satellites, in 2016 we don't know the location of coastline of Antarctica to the same level of accuracy that we already know the topography of Mars, Venus and our Moon.
Why are they so bad?
As usual there are lots of reasons. Most of the coastlines were mapped out by people on sailing ships and huskie drawn sledges decades before the satellites were launched. That means the outlines of the coasts and water depths tend to be excellent. But absolute position - basically the origin of the co-ordinate system - can be out.
The bottom line is if you are trying to calculate position with a sextant and clock, it's hard enough in good conditions (for me!). But in a snowstorm when it has been overcast for several days? The historical navigators are my heroes.
In practice today does this lack of accuracy matter?
That picture of the ship's track tells the story. The ship has skirted the coast of the island, but according to the chart we ended up on land! I have a few examples like this from Antarctica. And even the mighty Google Earth has Charcot Island wrong.
Polar ship Captains, officers and crews take ships into areas that are genuinely unexplored. We don't know the coastline or the water depths well.
In fact, in Antarctica all you really can be certain of is you know you are going to be surrounded by icebergs and sea ice.