Zachariae Isstrøm / Nioghalvfjerdsfjorden / NE Greenland

[Espen]

With the help of Wipneus, I now received my Petermann and Zachariae images printed on canvas and the result is fantastic, thanks Wipneus!!

The Petermann image is 1,3m x 1,3m
The Zachariae image is 1m x 1,5 m

The Petermann image even got a 3D effect (not intentionally).

The images are seen below (in reduced format).

The resolution is even so good I found new details I was not aware of.

[Wipneus]

The first Sentinel 1A IW high resolution (10m/pix) product was placed in the public archive today.
It is brilliant! Even when reducing the resolution to 25m there is just no comparison with best image until now: 2014 Oktober 5, 9 cycles * 12 = 108 days.

(click to download a 2.9MB animation)

[Espen]

Yes Wipneus that is a great image, it really shows what we can expect later in the season.

[A-Team]

Canvas? I have a few Zachariaes left in stock. Supplies won't last though. I make you special price?

[Espen]

That is a pretty rough canvas?

I am sure there is a market, they are really decorative, and very special!

The print shop who did the printing were impressed with the resolution.

[Wipneus]

Two 12 day cycles with the hi-res Greenland campaign are nearly over. Every place in Greenland should be imaged and archived at least 4 times, two from an ascending orbital position and two descending.

Not yet for Zachariae, there are two images in the public archive. One ascending and one descending.

The quality of the Ascending image that was added earlier today hast surprised me. I was already very happy with the Jan 21 image, but this is even a class better.

Here are two details, to show what I mean.

(click for higher resolution picture)

[Wipneus]

Part of the problem seems to be loss of information in processing the image. The source data file is/are a 16-bit grey scale TIFF's. When extracted using the "official" Sentinel Toolbox 8-bit RGB images get generated (tried png and tiff as ouputs). You would expects that the 16->8 bit transformation would be done while preserving as much detail as possible.
Trying to do this manually, using 16bit capable ImageMagick tools, I found I could do much better than that. Most of the glare in the Zachariae image form Jan 21 disappears this way exposing much more detail between the calvings and the ridged part of the glacier.

That means a lot more work for preparing these images, but quality will be much better than what I showed before (and what DMI and PolarView show).

At the moment I apply the following ImageMagick option to the raw image files:

-contrast-stretch 0x0.05%

(in short: perform a linear stretch from black to white, discarding at most 0% of the black pixels and 0.05 on the white side of the spectrum)

The resulting images can be processed further as 8-bit grey's in the Gimp.

[Wipneus]

Here is the first animation using all hi-res IW mode Sentinel images at 10m/pixel.
Images processed as described above. Movement between Jan 21 - Feb 14, 24 days or 2 Sentinel cycles, is 14 pix to the right and 7 pixels up. That translates to about 6.5 m/day.
It looks that the floating calving's, frozen together with sea ice, kept the front from several more calving's since the last one in October.

(click to start the big animation)

[Wipneus]

In the image above between the calving's are some are some that look as dark calving's. I am wondering what they are, they appear to be elevated above the surrounding rubble judging the highlight to their right side ( the satellite's radar beam shines from the right in its descending orbital path). But the sudden appearance of one in the south seems to incline they are just smooth pieces of sea ice.

[Espen]

Good question, my unqualified guess is, it is a slice from the "big calf" that turned up side down?
And in the same action pushed the "mother" away.

[Espen]

Here is the first animation using all hi-res IW mode Sentinel images at 10m/pixel.
Images processed as described above. Movement between Jan 21 - Feb 14, 24 days or 2 Sentinel cycles, is 14 pix to the right and 7 pixels up. That translates to about 6.5 m/day.
It looks that the floating calving's, frozen together with sea ice, kept the front from several more calving's since the last one in October.

(click to start the big animation)

It seems that Zachariae is preparing for a major calving soon?

[Shared Humanity]

Good question, my unqualified guess is, it is a slice from the "big calf" that turned up side down?
And in the same action pushed the "mother" away.

You eye for detail is amazing. It looks like that slice came from the calving face as there is a  noticeable area that receded just  adjacent to it.

[Espen]

Good question, my unqualified guess is, it is a slice from the "big calf" that turned up side down?
And in the same action pushed the "mother" away.

You eye for detail is amazing. It looks like that slice came from the calving face as there is a  noticeable area that receded just  adjacent to it.

Thanks SH, if that is true, we can conclude the "ice-cubes" with black tops are sliced baby-calves.

[nukefix]

Good question, my unqualified guess is, it is a slice from the "big calf" that turned up side down?
And in the same action pushed the "mother" away.

Yes, that's exactly what they are, the undersides of icebergs are so smooth that they do not reflect much microwaves back towards the radar.

[nukefix]

Part of the problem seems to be loss of information in processing the image. The source data file is/are a 16-bit grey scale TIFF's. When extracted using the "official" Sentinel Toolbox 8-bit RGB images get generated (tried png and tiff as ouputs). You would expects that the 16->8 bit transformation would be done while preserving as much detail as possible.

Hmm cannot you export as "Generic binary" from the S1TBX to save all the bits?

[Wipneus]

Hmm cannot you export as "Generic binary" from the S1TBX to save all the bits?

I am not sure how it would help to convert a specified binary (the SAFE product) to an unspecified binary blob. Disadvantages are that the size is blown up by six(seems to convert 16bits grey to 3*32bits RGB). It does not seem to export views created in the toolbox, just the original product.

[nukefix]

Hmm cannot you export as "Generic binary" from the S1TBX to save all the bits?

I am not sure how it would help to convert a specified binary (the SAFE product) to an unspecified binary blob. Disadvantages are that the size is blown up by six(seems to convert 16bits grey to 3*32bits RGB). It does not seem to export views created in the toolbox, just the original product.

You can crop the original product by selecting "Spatial Subset from View" to generate a new product covering just your area of interest. I guess the image-export from the toolbox does not allow one to select the number of bits to be used in the jpeg/tiff/png?

[Wipneus]

 I guess the image-export from the toolbox does not allow one to select the number of bits to be used in the jpeg/tiff/png?

I have not found it.
8 bits is fine though. But I did not find anything to tune (or stop) the capping of the high intensities, thus loosing the information in highly reflecting areas like glaciers. I would expect the scaling option to do the trick (right click on the band and choose "Scale Data") but nothing seems to change.

[nukefix]

 I guess the image-export from the toolbox does not allow one to select the number of bits to be used in the jpeg/tiff/png?

I have not found it.
8 bits is fine though. But I did not find anything to tune (or stop) the capping of the high intensities, thus loosing the information in highly reflecting areas like glaciers. I would expect the scaling option to do the trick (right click on the band and choose "Scale Data") but nothing seems to change.

In the menus there is Utilities - Dataset Conversion - Convert Datatype with some parameters related to scaling, perhaps that would work?

[Espen]

It is amazing how Sentinel is avoiding Zachariae, I am curious to know why?

http://www.polarview.aq/arctic

[Wipneus]

It is amazing how Sentinel is avoiding Zachariae, I am curious to know why?

http://www.polarview.aq/arctic

No, I have noticed the same since the data became available.

Bad news: it is getting worse. In the next two cycles (cycle 41 Feb 21-26 and cycle 42 Feb 26- Mar 10) no IW sensor mode (== hi resolution) data aquisition is planned, except for the Jacobshavn spot.
I don't know why cycle 41 is only 6 days long ( the Sentinel cycle is 12 days) nor why the ESA planners call this ramping up. Hopefully because this is just a bad dream.

They do plan to do the full Antarctic coast though.

https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario

[nukefix]

THe dedicatesd campaign seems to be over so EW is the best we'll get for the foreseeable future. It's too bad there is no Copernicus climate service yet that would require frequent IW-coverage of ice sheet margins..

[Wipneus]

THe dedicatesd campaign seems to be over so EW is the best we'll get for the foreseeable future.

resulting in (only) one pair of same orbital position IW Ground Range Detected products over the Zachariae area. There are additional Single Look Complex (SLC) products, that should be convertible to GRD. The SLC->GRD function in the toolbox requires inputs that are beyond my understandings.
If anyone can help that would be much appreciated.

[Wipneus]

A medium resolution EW image shows that the expected calving has not happened yet.

(click for a bigger picture)

[nukefix]

resulting in (only) one pair of same orbital position IW Ground Range Detected products over the Zachariae area. There are additional Single Look Complex (SLC) products, that should be convertible to GRD. The SLC->GRD function in the toolbox requires inputs that are beyond my understandings.
If anyone can help that would be much appreciated.

In SLC to GRD conversion you basically can leave all the parameters in the default settings. The only parameter you might want to fiddle with is Multilook with which you can set the desired output pixel size. When you change the number of range-looks it calculates the required azimuth looks for generating square pixels automatically. 4 range and 1 azimuth looks results in 14m pixel size while 6 range and 2 azimuth gives 25 meters.

[Wipneus]

This is how far I come:

1) select the SLC->GRD function
2) in the first tab select a SLC product (the SAFE.zip file);

Now I get the error message when I try to prceed:

  2-Calibration: no output product is selected

Tab2 is called 2-Calibratio2, but there is nothing that I can select or enter in that tab as an output product.
Under Tab5, you can specify an output name, but whatever I enter there does not get me any further.

Something very obvious escapes me, but what is the program trying to say?

[nukefix]

This is how far I come:

1) select the SLC->GRD function
2) in the first tab select a SLC product (the SAFE.zip file);

Now I get the error message when I try to prceed:

  2-Calibration: no output product is selected

Tab2 is called 2-Calibratio2, but there is nothing that I can select or enter in that tab as an output product.
Under Tab5, you can specify an output name, but whatever I enter there does not get me any further.

Something very obvious escapes me, but what is the program trying to say?

Did you select the channel? I think you need to select it even if there's only one..

[Wipneus]

Did you select the channel? I think you need to select it even if there's only one..

Very logical idea, tried everything but no way to select a source band (nearest thing to channel that I can find) in the SLC2GRD dialog. I would expect something selectable, or entereable, in the "Source Band" boxes. Should it??

Selecting bands outside the dialog does not do anything.

[nukefix]

I think you are confusing the toolbox by selecting a SAFE-product as the source. Instead you should 1st import the SAFE-product so that it's opened in product view, and then select SLC to GRD from the menus when the imported product is active.

[Wipneus]

I think you are confusing the toolbox by selecting a SAFE-product as the source. Instead you should 1st import the SAFE-product so that it's opened in product view, and then select SLC to GRD from the menus when the imported product is active.

Again very logical, the result is exactly the same.

I found my problem now, and as expected it is very stupid and embarrassing: there is another menu item, one layer deeper, that does "Sentinel SLC to GRD conversion". It is now grinding the raster data.

With your help I can go further now, thanks a lot.

[sidd]

Heres some Nioghalvfjerdsfjorden and Zach contourage from morlinghem, right way up even, deeper holes in the south inland of Zach, no wonder Nioghalvfjerdsfjorden aint doin much tho the tongue is afloat

holes aint so deep compared to down Jacobshawn way

sidd

[Wipneus]

Bad news: it is getting worse. In the next two cycles (cycle 41 Feb 21-26 and cycle 42 Feb 26- Mar 10) no IW sensor mode (== hi resolution) data aquisition is planned, except for the Jacobshavn spot.
I don't know why cycle 41 is only 6 days long ( the Sentinel cycle is 12 days) nor why the ESA planners call this ramping up. Hopefully because this is just a bad dream.

Perhaps bad dream is the explanation. A few IW slices, acquired on Feb 26 appeared in the public archive. Not the Zachariae area yet.

[A-Team]

sidd, on the Zach contourage, could you possibly include more farther to the south and west, pick up more of the ice stream? It diagonals in from the southwest.

I am seeing -500 m and -600 m but not their contextual continuation or maximal depth. Also, could you prepare a companion image without the number overlay?

Right you are, Jakobshavn hit -1634 m below sea level on Jim's clip. Now that is a serious hole. Over a mile deep (5361'). Plus whatever saturated till sitting above bedrock.

I wonder if Morlighem would be willing to add the experimental velocity map at the same gridding and projection. It might be up there at NSIDC under some different project name. I am curious as to whether the velocities know about these holes.

[Jim Hunt]

sidd, on the Zach contourage, could you possibly include more farther to the south and west, pick up more of the ice stream? It diagonals in from the southwest.

Right you are, Jakobshavn hit -1634 m below sea level on Jim's clip. Now that is a serious hole. Over a mile deep (5361').

This will all be easy peasy, once the right proj4 settings become apparent!

[Wipneus]

Zachariae seen by Sentinel 1A in IW mode on Feb 14 and 26. A large area  with calvings, sea ice and rubble is moving with the glacier.

Click that picture for a 20m/pix resolution animation.

[Espen]

Yes Zachy is amazing, I wonder where she will take us this season and she is well up in speed already.

[Espen]

Here is some more info:

(It explains some of the surface seen at Zachariae. and we will soon see some "growing" rocks)

The Landsat image is from September 30 2014.

[sidd]

surface velocity map compared to contouring, green is 0, blue is deeper, 100 m interval .
The velocities are larger over deeper beds, almost can pick out each tail and split

[Espen]

First image of Zachariae Isstrøm by Modis:

[A-Team]

Here is an interesting Palsar interferometric image of mid-Zachariae. No explanation provided but it seems to be showing shear lines in the upper ice stream (Negis). Their interest seems to be in characterizing firn and snow accumulation; I've not seen any actual glaciology papers emerge from this to date.

http://web.stanford.edu/~acchen/AGUFall2009Poster.pdf
http://web.stanford.edu/group/radar/people/Albert_thesis_small.pdf
http://scholar.google.com/citations?user=Eq1R1XUAAAAJ&hl=en
http://uavsar.jpl.nasa.gov/science/workshops/presentations2013/UAVSAR_WorkShop2013_Greeland_%28Chen%29.pdf

[nukefix]

A plain interferogram shows DEM and ice-movement effects mixed together so it can be difficult to interpret. In the fast-moving ice-stream the "fringes" show differential displacement (in the range-direction of the radar) due to movement. 1 fringe corresponds to half of a wavelength ~= 12cm in the Palsar case.

[Wipneus]

No hi-res Sentinel-1 images over the Zachariae area planned over the next month or so. We will have work with the much lower res EW data that is occasionally obtained.
Here we see that the new calving is basically complete, the frozen mix downstream prevents it separating from the glacier.

[Wipneus]

A sequence of Sentinel images from Jan 15 and March 16. Separation is 60 days or 5 Sentinel orbit cycles. Due to the low (40m/pix) resolution I can not say more than the glacier velocity is still 6m/day. Perhaps a minor calving can be seen on the southern edge.

(must click to start the animation)

[Espen]

There is a lot more calving potential ahead, over the whole front.

[Espen]

Zach is back on the Landsat-stage, here we see September 30 2014 vs March 16 2015.

At first glance nothing is seen, because the whole lot moved in the meantime, but look carefully, September 30 got 2 rows of main debris where as March 16 2015 got 3 rows in front of the calving area.
One more thing to check is the substantial damage at the south of the calving front, just north of the future Kap Zach / Zach Island *):

It is not every day you can name an Island or a Kap

[Wipneus]

Zachariae before and after the Arctic winter seen by Landsat 8. The calving front has not changed so much, but two calvings were in between. The glacier has continued to move at a speed of about 6m/day.

(click to see the 2.5MB animation)

[Wipneus]

Latest low res Sentinel 1 image, shown compared with 36 days ago. The cracks of the next calving getting longer both on the north and the south side.

(click to see the animation)

[Espen]

Wipneus, it is very interesting what happens around Kap Zach or Zach Island in the south, that will make the shape of the calving front much different to what is today.

[Wipneus]

Never a dull moment at Kape Zach.

[Laurent]

Do not forget to click as usual