Tag Archives: MODIS

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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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.

Worldview opening screen.
Worldview opening screen.

I do recommend following the tour to find your way around the data sets.

Worldview tour screen
Worldview tour screen

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.

Some of the data choices available in WorldView
Some of the data choices available in Worldview

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

Worldview Antarctic stereographic view.
Worldview Antarctic stereographic 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.

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The Prince Gustav Channel was covered by an ice shelf which collapsed in the 1990's, and for many years it was possible to sail a ship around James Ross Island.

Recently it has been covered with sea ice frozen to the land - we call this fast ice, and it's usually only a few metres thick of frozen sea water - rather than hundreds of metres thick snow derived ice shelf.

Recent images from the TERRA satellite show that this fast sea ice is finally breaking out.

It'll soon be possible to circumnavigate James Ross Island once more.

The Prince Gustav Channel early spring Antarctic summer 2016/7 from MODIS satellite imagery on the TERRA satellite.
The Prince Gustav Channel early spring Antarctic summer 2016/7 from MODIS satellite imagery on the TERRA satellite.

This map shows the location of the channel.

The Antarctic Peninsula showing the location of the Prince Gustav Channel.
The Antarctic Peninsula showing the location of the Prince Gustav Channel.

Now it has started I wonder how long it will take to finally clear. Or more fun, I wonder if tour ships will be able to get around the island?

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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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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 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.

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The low sea ice extent I noticed in my previous blog post about Antarctic Sound has extended southwards along the east side of the Antarctic Peninsula.

The sea ice extent along the Antarctic Peninsula 24 September 2016
The sea ice extent along the Antarctic Peninsula 24 September 2016. Data from DMSP SSMIS

The open water that shows up as black in the image above extends to at least as far south as the Antarctic Circle (66° 33′S). Open water along this part of the Antarctic Peninsula is unusual at any time of the year let alone the height of winter. The image below is from the National Snow and Ice Data Centre. It shows  sea ice extent >15% with an outline of the typical extent for that day based on a 30-year (1981-2010) median (orange line).

NSIDC Antarctic sea ice extent 24 September 2016 with the median extent (1981-2010) for this day.
NSIDC Antarctic sea ice extent 24 September 2016 with the median extent (1981-2010) for this day.

You can see how unusual this observation is, and I wrote a general post Antarctic Sea Ice Extent a while ago.

The open water is also very clear in the MODIS imagery as the black wedge between the Antarctic Peninsula, and the sea ice of the Weddell Sea.

The MODIS imagery for the Antarctic Peninsula 25 September 2016.
The MODIS imagery for the Antarctic Peninsula 25 September 2016.

In my previous post I pointed at weather systems as likely being responsible. Now to me it looks like a large system is pushing the whole Weddell Sea sea ice to the east and away from Antarctic Peninsula.

There is always some open water in the pack ice at any time of the year, but it's clear that their is a pathway south right now. I imagine it will close soon and wouldn't be keen to be on a ship in that open water heading south.

What is interesting is the heat transfer from the ocean to the atmosphere that far south at this time of the year will be huge. This is what I wrote about that heat loss for the Arctic.

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Just noticed this on the MODIS  sensor on the TERRA satellite image from 10 September 2016.  (Tile Antarctica_rc05c01 if you are interested in that sort of thing)

Antarctic Sound on the tip of the Antarctic Peninsula 10 Sept 2016
Antarctic Sound on the tip of the Antarctic Peninsula 10 Sept 2016

The Antarctic sea ice ice extent map for 10 September 2016 shows an interesting and large low concentration right at the tip of the Antarctic Peninsula

The sea ice extent around Antarctic 10 September 2016. Yellow box is roughly where the MODIS image is, and Antarctic Sound is labelled. Data from DMSP SMMI
The sea ice extent around Antarctic 10 September 2016. Yellow box is roughly where the MODIS image is, and Antarctic Sound is labelled. Data from DMSP SMMI

So why the missing sea ice at the top of the Peninsula?  It could be a storm, or could be heat from the ocean keeping the area ice free. I'll have a look at the data when I've time, but for now I would bet on the ocean.

Interestingly historically it has been a bit of a tough place. Otto Nordenskjöld navigated the sound in December 1902 on the Swedish Antarctic Expedition before their ship, the Antarctic was crushed and lost. They were stranded for two years...

Yet more beautiful MODIS imagery showing some wonderful patterns in a plankton bloom in the Barents Sea.

Plankton patterns in the Barents Sea
Plankton patterns in the Barents Sea

The screen grab is from the 250m resolution imagery, and the whole arctic panel shows just where the bloom is located.

The Arctic on 29 July 2015 in MODIS imagery
The Arctic on 29 July 2015 in MODIS imagery

This particular region seems to show plankton blooms regularly in the MODIS imagery and the Wikipedia page has a similar (but not as nice) image dated summer 2009.

 

 

There is a lot happening at the edge of the Greenland Ice Sheet as summer progresses, and the MODIS sensor on the TERRA and AQUA satellites is a wonderful way to observe it.

I noticed the other day (8 July 2015) this beautiful image of fast ice breaking out of a Fjord on the east coast at 76N

Fast ice breaking out of an East Greenland fjord
Fast ice breaking out of an East Greenland fjord

The full image can get down to 250 m per pixel and it is amazing stuff. The image below (from Google Earth) shows the location.

Location of the enlargment
Location of the enlargement

And now in the 9 July MODIS image you can see very many large pools of water on the edge of the Greenland Ice sheet. Again, remember each pixel of this image is 250 m across - they look small but that are large pools.

...continue reading