Tag Archives: antarctica

At this time of the year we should expect the Antarctic sea ice to be growing rapidly, but after the historic lows of last Antarctic summer, we can see that whilst it is rapidly advancing, the sea ice extent (the area of ocean covered by >15% of sea ice) it is still ~1 ¼ million km2 below the median from 1981-2010.

Antarctic sea ice extent (with greater >15% sea ice cover) 15 May 2017. From NSIDC.
Antarctic sea ice extent (with greater >15% sea ice cover) 13 May 2017. From NSIDC.

There is not a consistent trend in Antarctic sea ice extent, and much regional interannual variability. The plot below shows the sea ice extent on 13 May for each of the years 1989-95, and 13 May 2017.

Antarctic sea ice extent on 13 May for the years 1989, 1990, 1991, 1992, 1993, 1994, 1995 and 2017. Data from DMSP SMMI.
Antarctic sea ice extent on 13 May for the years 1989, 1990, 1991, 1992, 1993, 1994, 1995 and 2017. Data from DMSP SMMI.

The image above shows the sort of variability we expect in the Antarctic sea ice extent. It is helpful too to see where the sea is currently is and isn't compared with the mean from 1989-93.

The mean Antarctic sea ice for the years 1989-93 on 13 May, the sea ice concentration on 13 May 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 13 May, the sea ice concentration on 13 May 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 regions in May 2017 with the greatest deficit of sea ice remain the Amundsen and Ross Sea, and the Eastern Weddell Sea and off the coast of Dronning Maud land. As I said in my last Antarctic sea ice post it is likely the freeze up is delayed because of the heat gained by the ocean in the Antarctic summer of 2016/17.

You can also see in the South West Weddell Sea the Ronne Polynya I wrote about in March 2017 is still seen in the sea ice concentration data. In the visible satellite data you can also see this open water.

The Ronne Polynya can see seen in the South West Weddell Sea satellite data on 15 May 2017. The box marks the approximate image of the SAR image below.
The Ronne Polynya can see seen in the South West Weddell Sea satellite data on 15 May 2017. The box marks the approximate image of the SAR image below.

In the Sentinel 1 SAR data from the 15 May (From PolarView), the growth of the sea ice in the polynya is clear.

Sentinel 1 Synthetic Aperture Radar (SAR) Image 15 May 2017 in the South West Weddell Sea. From PolarView.
Sentinel 1 Synthetic Aperture Radar (SAR) Image 15 May 2017 in the South West Weddell Sea. From PolarView.

This ice growth is important for the ocean as it means the salinity of the waters just beneath the sea ice will be increasing.

I'll keep watching the polynya to see if and when it closes up. And I will also keep looking at the sea ice.

 

The polynya I saw forming in early February is still clear, and very large in the Southern Weddell Sea. At the moment it is more than than 80,000 km2, although there is clearly a lot of young sea ice covering a large part of the polynya.

The Weddell Sea 5 March 2017 in the Terra MODIS true colour image.
The Weddell Sea 5 March 2017 in the Terra MODIS true colour image.

In my original post I said this was likely formed by winds from the Ronne Ice Shelf.

Well Dr Stef Lhermitte (Delft) has put together the most amazing movie showing the development of the polynya over January and February. It shows satellite sea ice data with winds from the ECMWF overlain.

You can clearly see the winds pushing the sea ice away from the ice shelf as time progresses.

It is just as @StefLhermitte said in his tweet yesterday:

...continue reading

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Trying to understand the geographic nature of the very low Antarctic sea ice extent I made the following animation:

Antarctic sea ice extent on 1 March for the years 1989, 1990, 1991, 1992, 1993, 1994, 1995 and 2017. Data from DMSP SMMI.
Antarctic sea ice extent on 1 March for the years 1989, 1990, 1991, 1992, 1993, 1994, 1995 and 2017. Data from DMSP SMMI.

The highlight issues in the graphic are the clear lack of sea ice in the Amundsen/Ross Seas and the Southern Ocean off Dronning Maud land. (If you are not familiar with the names off the seas / locations see the map below).

The Weddell Sea is has a relatively compressed sea ice cover this year - but it's clear there is large inter-annual variability.

Off Wilkes Land the sea ice is heavier this year - and it's easy for this to get lost in the headline story around the very low extent. There are several Antarctic research stations along this coast:

The French Station Dumont d’Urville,

Two Australian Stations of Casey and Davis,

and the Russian Mirny Station.

Here is the NSDIC Antarctic sea ice extent 1 March 2017.

Antarctic sea ice extent (with greater >15% sea ice cover) 1 March 2017. From NSIDC.
Antarctic sea ice extent (with greater >15% sea ice cover) 1 March 2017. From NSIDC.

And finally the promised map from the National Snow and Ice Data Center (NSIDC) with regional seas and other features marked.

The oceans and regional seas around Antarctica, along with other geographical features. From NSIDC.
The oceans and regional seas around Antarctica, along with other geographical features. From NSIDC.

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I noticed yesterday that a polynya had formed in front of the Ronne Ice Shelf over the last 2 weeks.

Screengrab from NASA Worldview 17 February 2017
Screengrab from NASA Worldview 17 February 2017

In that image it is about 27,000 kmin area.

I mapped the opening of the polynya from MODIS imagery over the last two weeks. There is cloud in the images but the opening of the polynya is fairly clear.

Formation of the Ronne Polynya 30 January to 14 February 2017.
Formation of the Ronne Polynya 30 January to 14 February 2017.

On 31 January 2017 there is no open water, but then over the 16 day period it opens to the ~27,000 kmin area. If you're eagle eyed you can see that there is thin frazil ice forming in the open water in front of the ice shelf at the end of the sequence.

So what caused it?

...continue reading

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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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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.

Today is 105 years since Roald Amundsen, Helmer Hanssen, Sverre Hassel, Oscar Wisting and  Olav Bjaaland reached the South Pole. And Google have celebrated that fact with a google Doodle:

Amundsen expedition South Pole Google Doodle
Amundsen expedition South Pole Google Doodle

I love the doodle. It's beautiful art.

But it falls on me to be a bit of a bore...

The doodle shows mountains, and south pole is on an extremely flat plateau. Amundsen named it the King Haakon VII's Plateau.

The doodle shows it's snowing quite heavily. Actually South Pole is technically a desert, and almost no snow falls. The snow does drift in the winds though.

The doodle shows it's dark... The sun comes above the horizon at South Pole in September and it doesn't set until March. When Amundsen and the team arrived it would have been 24 hour daylight.

...continue reading

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RRS James Clark Ross is on route to Rothera, the largest British Antarctic Survey research Station. In the next few hours to get to the base she will have to pass what looks like a continuous sea ice band about 15 km wide, before she enters some looser pack. To get their she will have to do some icebreaking. The band of ice has been stationary for over a week.

If you want to follow the action the ship has a webcam, or you can check the Radio Office Mike Gloistein's update page. The web cam is as I write this but I'm sure it will be switched on soon.

The MODIS satellite image off Adelaide Island 25 Nov 2016, with the location of the RRS James Clark Ross 0000 28 November 2016.
The MODIS satellite image off Adelaide Island 25 Nov 2016, with the location of the RRS James Clark Ross 0000 28 November 2016.

The satellite image is from 25 November 2016, but the sea ice doesn't look like it has changed significantly since then. I chose that date simply because it is relatively cloud free.

The ship has about 130 km to run so could dock later today - but it could be tomorrow given the sea ice.  The path I have shown in red looks quite a long way south of the Island - but close in it gets quite shallow. If your interested in your polar history the ship RRS John Biscoe was actually abandoned in this region for a while before being rescued by the German ship Polarstern.

This is as The Antarctic Report points out, quite early for the ship to reach the base.

The track of the ship is online along with the weather conditions it is experiencing. At at about 0°C it is currently warmer than a lot of the UK.

Dr Helen Jones is the doctor on the James Clark Ross and she is writing a blog Baby it's cold down here.

--UPDATE 1050z --

You can see James Clark Ross is now in the ice and heading for the band of relatively open water at the southern tip of Adelaide Island.

This is an image from the webcam.

I wrote about what a water sky is a while ago.

--UPDATE 0650z 29 November --

It was too early and the RRS James Clark Ross didn't make Rothera.

To quote the radio officer Mike Gloistein:

The sea-ice around the bottom of Adelaide Island has been heavy and whilst (for those of you who look at the satellite pictures) there are some leads and areas of open water,  they are close to land and if we took that route (which also includes shallow water and rocks) and the weather then pushed the ice inland,  the ship could easily become stuck between a rock and a hard place.

And get stuck just like the John Biscoe...

 

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The seasonal cycle of sea ice extent in Antarctica has been fairly stable over the length of the satellite record.  There is a slow growth of sea ice from a minimum of ~3x106 km2 in February to a maximum of ~19 x106km2 in September, before there is a relatively rapid fall in the Antarctic spring.

But this year something different is happening.

Below is Tamino's image for the Southern Hemisphere sea ice extent, the red line is 2016 up to 16 November 2016.

The annotated seasonal extent of sea ice in the Southern hemisphere. From Tamino's post Sea Ice, North and South.
The annotated seasonal extent of sea ice in the Southern hemisphere. From Tamino's post Sea Ice, North and South.

From January up to September the sea ice extent in 2016 follows all previous data.

But what happened in September?

...continue reading