Tag Archives: Amundsen Sea

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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:

Antarctic sea ice extent 12 Feb 2017 & diff from mean 1989-93 on same day. Blues imply more ice and reds imply less compared with the mean.
Antarctic sea ice extent 12 Feb 2017 & diff from mean 1989-93 on same day. Blues imply more ice and reds imply less compared with the mean.

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:

Antarctic sea ice extent. Downloaded from NSIDC 14 February 2017.
Antarctic sea ice extent. Downloaded from NSIDC 14 February 2017.

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:

The Antarctic sea ice extent 1 January to 12 February 2017. Data from DMSP SMMI
The Antarctic sea ice extent 1 January to 12 February 2017. Data from DMSP SMMI

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.

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.
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.

Not long until the Antarctic sea ice minimum.

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 mean Antarctic sea ice for the years 1989-93 on 22 January, the sea ice concentration on 22 January 2017 and the difference between the two data sets. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.
The mean Antarctic sea ice for the years 1989-93 on 22 January, the sea ice concentration on 22 January 2017 and the difference between the two data sets. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.

The Amundsen Sea has very low sea ice

Amundsen Sea has very low sea ice in January 2017
Amundsen Sea has very low sea ice in January 2017

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.

Sea ice extent is currently relatively high in the Bellingshausen Sea.
Sea ice extent is currently relatively high in the Bellingshausen Sea.

Nevertheless, as expected, it was possible to finally relieve the British Antarctic Survey Rothera Base in January.

The Weddell Sea is a game of two halves

Sea ice in the Weddell Sea is now compressed against the Antarctic Peninsula
Sea ice in the Weddell Sea is now compressed against the Antarctic Peninsula

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.

MODIS image from the TERRA satellite 23 January 2017. The sea ice edge in the Weddell Sea is very sharp.
MODIS image from the TERRA satellite 23 January 2017. The sea ice edge in the Weddell Sea is very sharp.

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.

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My previous posts on Amundsen Sea Polynya and their development showed ~37,600 km2 of open water in front of the ice shelves. It is very early spring in Antarctica at this time of the year and it’s still cold.

That means sea ice can still grow.

This is the Dotson Getz polynya on 9 October 2016. It has a perimeter of ~800 km and an area of ~25,500 km2.

The Dotson Getz polynya on 9 October 2016. Open water is black and streaks of sea ice growth are clear. The location of the Bear Peninsula Automatic Weather Station is marked.
The Dotson Getz polynya on 9 October 2016. Open water is black and streaks of sea ice growth are clear. The location of the Bear Peninsula Automatic Weather Station is marked.

I put together the satellite data from 9-12 October 2016 and it shows extremely rapid sea ice growth.

...continue reading

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I was interested in how long the polynya I blogged about yesterday had existed.

I made a gif of the previous months sea ice data.

The sea ice extent in Pine Island Bay 11 September to 10 October 2016. Data from DMSP SSMI. The development of the polynya can be seen in the development of the dark regions.
The sea ice extent in Pine Island Bay 11 September to 10 October 2016. Data from DMSP SSMI. The development of the polynya can be seen in the growth of the dark regions.

You can see that the polynya in the centre of the picture can be seen from the very beginning. This is forming in front of the Dotson Ice Shelf  - and from the scale bar you can see it is big. This polynya really starts to develop as open water around 5 October 2016.

The coastal polynya on the northern land boundary appear in mid September - and develop throughout the record.

The image below was in my previous post and it shows the three polynya from a MODIS image on 9 October 2016.

The MODIS imagery 9 October 2016 from the TERRA satellite overlain in Google Earth
The MODIS imagery 9 October 2016 from the TERRA satellite overlain in Google Earth

Next diversion will be a area of open water / time plot.

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The Amundsen Sea currently has some very large polynya. In front of the Dotson, Getz and Pine Island ice shelves they are clear in the satellite data.

The sea ice extent along the Antarctic Peninsula 2 October 2016. Data from DMSP SSMI
The sea ice extent along the Antarctic Peninsula 9 October 2016. Data from DMSP SSMI.

polynya is an area of open water in the winter pack ice.

These are likely latent heat polynya, and strong winds are pushing the sea ice away from the coasts to make the open water.  In the open water there will be a lot of sea ice generation. I wouldn't be surprised if the weather that is keeping the sea ice compressed against the Antarctic Peninsula is also responsible for opening them.

Taking the MODIS data from the TERRA satellite and importing that into google earth, the open water shows up as black. At the top of the image in front of Pine Island Glacier the polynya are partially obscured by cloud.

In Google Earth you can measure the area quite easily.

...continue reading