Tag Archives: satellite

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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...

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The MODIS sensor satellite imagery is showing a beautiful and evolving large plankton bloom in the Chukchi Sea at the moment.

Plankton bloom in the Chukchi Sea, as seen in the MODIS sensor on 23 June 2015.
Plankton bloom in the Chukchi Sea, as seen in the MODIS sensor on 23 June 2015. Alaska is on the LEFT and Russia the RIGHT. The image is looking SOUTH.

The plankton are the lighter green bands I've labelled and the full image is available at an astonishing 250m resolution.

...continue reading

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I very much like looking at the AQUA and TERRA MODIS sensor images every now and then. Today I saw this beautiful image off the southern tip of Greenland which was captured on 23rd February 2015.

Sea ice off Cape Farewell
Sea ice off Cape Farewell, Greenland

What you are looking at are three different white things: snow on Greenland, clouds and my favorite of course, the sea ice. You may find it hard to pick out the different white features. This is because it is a true colour image.

But as the MODIS web site says:

[the] detectors measure 36 spectral bands between 0.405 and 14.385 µm, and it acquires data at three spatial resolutions -- 250m, 500m, and 1,000m.

...continue reading

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This plot shows the Antarctic sea ice extent, the Arctic sea ice extent, and the total sea ice extent plotted against time.

Arctic, Antarctic and total sea ice extent 2012

Like in previous post I chose 2012 only because it is the most recent complete year in this data set.

Take a look at the minimum, the maximum and the range of the sea ice extent.

Antarctic: Minimum Antarctic sea ice extent 3.11 x 106 km2
Maximum Antarctic sea ice extent 19.48 x 106 km2
Range of the Antarctic sea ice extent 16.37 x 106 km2
Arctic: Minimum Arctic sea ice extent 3.37 x 106 km2
Maximum Arctic sea ice extent 15.25 x 106 km2
Range of the Arctic sea ice extent 11.88 x 106 km2

The range of Antarctic sea ice extent is 16.37 x 106 km2, and the range of the Arctic sea ice extent is 11.88 x 106 km2.

The Antarctic and the Arctic do not "balance" in sea ice extent - the Antarctic variations are much larger.

Look at the shape of the annual cycle. I said previously that in the Antarctic the seasonal cycle of sea ice extent is not symmetrical. Sea ice grows slowly and steadily before decaying relatively rapidly: the melt period is shorter than the growth period.

In the Arctic the time sea ice grows is roughly similar to the time sea ice melts.

So they do not "balance". The seasonal cycles, ranges, minimums and maximums are  different,

The annual cycle of the Arctic and Antarctic sea ice extent is very different.

We know that the extent and thickness of the Arctic sea ice is decreasing. See for example what Tamino wrote in Feb 2014.

But what about the Antarctic? The extent of the sea ice has broken records for the satellite era. (This is a very funny article making some claims about what that means - if you want a clue what is the difference between glacial ice and frozen sea water?).

Some believe the observed reduction in the Arctic sea ice volume is balanced by the increase in the Antarctic sea ice extent. So we should look at the black line in the plot above.

I will get onto why I don't think that is a good idea in a coming post.

Here is the plot animated with 1 second = 10 days

 About the data

The data set is from the National Snow and Ice Data Center Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data.

 

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This is the 2012 sea ice extent for both the Arctic and the Antarctic. The day of year and the calendar day are at the bottom.

I chose 2012 only because it is the most recent complete year in this data set.

My reason for making this video is because there have been a couple of huge news stories recently about the West Antarctic Ice Sheet:

On 12 May 2014 we heard that for all intents and purposes the West Antarctic Ice sheet is doomed (here is the primary research which is open access).

Then on 19 May 2014 we were told that Cryosat observations had shown that the loss of ice from Antarctica had increased quite a lot (here is the primary research).

For excellent commentary on these stories you can visit Carbon Brief, or Antarctic glaciers.org.

But whenever there is a big story about the decay of the West Antarctic Ice Sheet - which remember is land based glacial ice, some instantly point to this being not important because sea ice in Antarctica has been at record levels.

People who suggest that the observed decrease in glacial ice is somehow balanced by the observed increase in Antarctic sea ice extent are wrong. The sea ice is generally only a couple of metres thick and it is telling us quite a different climate story.

Over the next few posts I will try and explain why the decrease of Arctic sea ice is not balanced by an increase in Antarctic sea ice extent, and why there is no contradiction in glacial ice at the edge of the Antarctic continent decaying whilst simultaneously the sea ice is  at record extent.

 

[If anyone want the clip, also the Arctic and Antarctic as separate files in various large sizes and formats just send me an email at my work address - you will find a link on the "About me" page. And I will send you a dropbox link. I am a big fan of Creative Commons and Open Educational Resources. ]

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The data is from the US Defense Meteorological Satellite Program (DMSP), and the data is freely accessible from the National Snow and Ice data Centre.

 

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I came across this brilliant Deep Sea News blog post about oil on troubled waters. It talks at length about how a surface film of oil damps out higher frequency surface waves and only the low frequency waves can propagate. The net effect is the sea feels calmer as the breaking waves are damped out.

The same thing happens in rough seas when ice forms. I took the picture below in Bellingshausen Sea.

A grease ice slick in the Bellingshausen Sea Antarctica
A grease ice slick in the Bellingshausen Sea Antarctica

What you are looking at is very thin slick made up of sea ice crystals in the open ocean (called grease ice). The layer of crystals only allows the low frequency waves to propagate - so you see these odd looking slowly propagating ripples.

...continue reading

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This morning I posted my 10,000 tweet.

Whilst I am not sure if 10,000 is significant, I pointed to the brilliant NASA Earth Observation www site which has a wonderful post today about the reduction of sea ice increasing phytoplankton growth in the Arctic. (Be sure to click the "image comparision" button on that page).

High chlorophyll in open water
Sat picture from 10 July 2011 showing milligrams of chlorophyll per cubic meter of seawater. From the Aqua Satellite

...continue reading