Monthly Archives: October 2016

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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

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It is October and it is the Arctic sea ice growing season. The MODIS imagery yesterday shows this beautiful image of sea ice on the North East Greenland coast.

North West Greenland in a MODIS image 5 October 2016
North East Greenland in a MODIS image 5 October 2016 from the TERRA satellite

The image below shows roughly where we are looking:

...continue reading

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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 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.
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. Image from NSIDC
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.

James Clark Ross making very slow progress in compressed sea ice in Marguerite Bay, the Western Antarctic Peninsula.
RRS James Clark Ross making very slow progress in compressed sea ice in Marguerite Bay, the Western Antarctic Peninsula 11 December 2004.

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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.
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
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.
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.
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.
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.