<p><img src="https://i.sstatic.net/TTPyN.jpg" alt="natural-color">
I found a natural-color image of the same area: 68.28 South, 60.47 East, North is up, resolution is 130m/px, which makes the whole image about 100 km x 100 km. Looking at the image i'd say that:</p>

<ul>
<li>sea ice is water with pieces of ice in it,</li>
<li>the boundary between the two regions is clear water, probably caused by winds and currents moving the floating ice away from the edge of the ice shelf.</li>
</ul>

<p>I got the image at <a href="http://apps.sentinel-hub.com/sentinel-playground/#lat=-68.10712566634318/lng=-60.3424072265625/zoom=9/preset=1_NATURAL_COLOR/layers=B04,B03,B02/maxcc=100/gain=0.3/time=2015-01-01|2016-11-21">Sentinel Playground</a> using 100% cloud filter, 0.3 gain and date selection of 2016-11-21.</p>

<p>EDIT: Added more info about the position, scale and orientation of the image.</p>

CC BY-SA 3.0
2017-01-24T14:09:25.987Z
The location is 68.28 South, 60.47 East, and the scale is about 130m/px. North is up in the image.
mkadunc
CC BY-SA 3.0
2017-01-24T14:39:06.187Z
OK great! The image makes much more sense to me now. Thanks! One quick question - is your image from visible light, IR, radar, or something else?
uhoh
CC BY-SA 3.0
2017-01-24T16:30:07.530Z
Side note: There's a distinction between sea ice and the ice of an ice shelf. The ice shelf is the extruded end of a glacier, snow and ice mounded on land over thousands of years and pushed out to sea; sea ice is the ice that has formed on top of the ocean. Sea ice is usually 1-2 meters; this region of Larsen C is about 1,100 meters thick. So there's a significant height difference for casting a shadow.
jeffronicus
CC BY-SA 3.0
2017-01-25T17:33:30.850Z
@jeffronicus I'm sure you are saying something illuminating but I'm not getting it. Every time I look at the image in the question, my brain tells me it's three dimensional, and the dark ribbon in the middle is a shadow. But it isn't, is it? Is the ice shelf also ~10% above the water, ~90% below?
uhoh
CC BY-SA 3.0
2017-01-25T17:43:27.960Z
I'm not an expert on radar sensing, but i think for a cast shadow to be visible in an image you'd need the light source direction to be different from viewing angle. Radar emits its own 'light', so unless the image has been orthorectified to change its apparent biewing angle, you won't see cast shadows on radar imagery. Also, for a couple of km long shadow on a cliff that's ~ 100m high, the illumination angle would need to be very low, definitely not consistent with sentinel-1, which i think is pointed more or less directly downwards.
mkadunc
CC BY-SA 3.0
2017-01-25T20:36:16.970Z
Ah, now I see the question better. The black area should be open sea between the ice shelf and the sea ice. Source images can be found at http://www.polarview.aq/arctic, choose SAR Imagery then Sentinel-1: "Sea ice typically reflects more of the radar energy emitted by the sensor than the surrounding ocean, which makes it easy to distinguish between the two. But the amount and character of reflected energy are functions of the physical properties of the sea ice, which can be quite complex; thus, it can be difficult to interpret radar images of sea ice."
jeffronicus
CC BY-SA 3.0
2017-01-26T01:29:15.613Z
@mkadunc Yep, of course I know you are right. It's an illusion and I'm trying to tell myself to stop seeing it. I think the fact that the area it is black in the image is what's making it seem so pronounced.
uhoh
CC BY-SA 3.0
2017-01-26T01:44:55.410Z
@jeffronicus wow that's a really handy website! OK I will have a look around and get more used to radar imagery, thanks!
uhoh
CC BY-SA 3.0
2017-01-24T13:29:27.990Z
2017-01-24T14:27:16.347Z
2017-01-24T14:27:16.347Z
mkadunc
<p>The false color image below shows synthetic aperture radar imaging from ESA's <a href="http://esamultimedia.esa.int/docs/EarthObservation/Sentinel-1_sheet_March2016.pdf" rel="nofollow noreferrer">Sentinel-1</a> satellite. The map from the 20-Jan-2017 BBC article <a href="http://www.bbc.com/news/science-environment-38686626" rel="nofollow noreferrer">Larsen ice crack continues to open up</a> illustrates the same general area.</p>

<p>The Larson C Ice Shelf is the large blue-ish region in the middle of the false-color radar image, and is labeled as such. The crack is the thin lighter line just above the red arrow.</p>

<p>Moving diagonally upwards to the right, the gray region is labeled "Sea Ice". Is this just much thinner but mostly solid ice, or water with pieces of ice in it? While the ice shelf seems relatively uniform in tone, the gray sea ice area has a mottled pattern.</p>

<p>Also the boundary between the two regions has what looks to me like some kind of 3D effect - the black, ribbon-like variable width region separating the two. Is this an effect of shadowing from oblique incidence? Is this actually the sidewall height of the ice shelf?</p>

<p>There is also some discussion of radar imaging of sea ice in <a href="https://earthscience.stackexchange.com/a/6821/6031">this answer</a>.</p>

<p><a href="https://i.sstatic.net/ONb9x.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ONb9x.png" alt="enter image description here"></a></p>

<p><strong>above:</strong> Cropped and enlarged highlight from <a href="http://esamultimedia.esa.int/docs/EarthObservation/Sentinel-1_sheet_March2016.pdf" rel="nofollow noreferrer">Sentinel-1</a> synthetic aperture radar image of the Larson C ice shelf, beginning of January 2017, found <a href="http://www.rekanbola.com/patahan-gunung-es-di-antartika-terus-meluas/" rel="nofollow noreferrer">here</a>. Image credit: ESA/EU/Copernicus</p>

<p><a href="https://i.sstatic.net/OThoR.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OThoR.jpg" alt="enter image description here"></a></p>

<p><strong>above:</strong> <a href="http://esamultimedia.esa.int/docs/EarthObservation/Sentinel-1_sheet_March2016.pdf" rel="nofollow noreferrer">Sentinel-1</a> synthetic aperture radar image of the Larson C ice shelf, beginning of January 2017, found <a href="http://www.rekanbola.com/patahan-gunung-es-di-antartika-terus-meluas/" rel="nofollow noreferrer">here</a>. Open in separate viewer or tab for full size. The width of the image is roughly 300km, south is towards the lower right. Image credit: ESA/EU/Copernicus</p>

<p><a href="https://i.sstatic.net/2bSRB.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2bSRB.png" alt="enter image description here"></a></p>

<p><strong>above:</strong> Map of the region around the Larson C ice shelf, beginning of January 2017, from <a href="http://www.bbc.com/news/science-environment-38686626" rel="nofollow noreferrer">BBC here</a>. Image credit: MIDAS Project, A. Luckman, Swansea University. Because it's difficult to read, I'll point out that Wales not shown in it's correct location - it's there for scale only.</p>

<glaciology><remote-sensing><sea-ice><ice-shelf>
Need help understanding this satellite image of Larson C ice shelf
uhoh
# Need help understanding this satellite image of Larson C ice shelf

(Asked by: username_0 on 2017-01-24)

The false color image below shows synthetic aperture radar imaging from ESA's [Sentinel-1](http://esamultimedia.esa.int/docs/EarthObservation/Sentinel-1_sheet_March2016.pdf) satellite. The map from the 20-Jan-2017 BBC article [Larsen ice crack continues to open up](http://www.bbc.com/news/science-environment-38686626) illustrates the same general area.

The Larson C Ice Shelf is the large blue-ish region in the middle of the false-color radar image, and is labeled as such. The crack is the thin lighter line just above the red arrow.

Moving diagonally upwards to the right, the gray region is labeled "Sea Ice". Is this just much thinner but mostly solid ice, or water with pieces of ice in it? While the ice shelf seems relatively uniform in tone, the gray sea ice area has a mottled pattern.

Also the boundary between the two regions has what looks to me like some kind of 3D effect - the black, ribbon-like variable width region separating the two. Is this an effect of shadowing from oblique incidence? Is this actually the sidewall height of the ice shelf?

There is also some discussion of radar imaging of sea ice in [this answer](https://earthscience.stackexchange.com/a/6821/6031).

[![enter image description here](https://i.sstatic.net/ONb9x.png)](https://i.sstatic.net/ONb9x.png)

**above:** Cropped and enlarged highlight from [Sentinel-1](http://esamultimedia.esa.int/docs/EarthObservation/Sentinel-1_sheet_March2016.pdf) synthetic aperture radar image of the Larson C ice shelf, beginning of January 2017, found [here](http://www.rekanbola.com/patahan-gunung-es-di-antartika-terus-meluas/). Image credit: ESA/EU/Copernicus

[![enter image description here](https://i.sstatic.net/OThoR.jpg)](https://i.sstatic.net/OThoR.jpg)

**above:** [Sentinel-1](http://esamultimedia.esa.int/docs/EarthObservation/Sentinel-1_sheet_March2016.pdf) synthetic aperture radar image of the Larson C ice shelf, beginning of January 2017, found [here](http://www.rekanbola.com/patahan-gunung-es-di-antartika-terus-meluas/). Open in separate viewer or tab for full size. The width of the image is roughly 300km, south is towards the lower right. Image credit: ESA/EU/Copernicus

[![enter image description here](https://i.sstatic.net/2bSRB.png)](https://i.sstatic.net/2bSRB.png)

**above:** Map of the region around the Larson C ice shelf, beginning of January 2017, from [BBC here](http://www.bbc.com/news/science-environment-38686626). Image credit: MIDAS Project, A. Luckman, Swansea University. Because it's difficult to read, I'll point out that Wales not shown in it's correct location - it's there for scale only.

**Tags:** glaciology, remote-sensing, sea-ice, ice-shelf


---

## 1 answers

### Answer by username_1 on 2017-01-24. Score: 6 | Accepted answer

![natural-color](https://i.sstatic.net/TTPyN.jpg)
I found a natural-color image of the same area: 68.28 South, 60.47 East, North is up, resolution is 130m/px, which makes the whole image about 100 km x 100 km. Looking at the image i'd say that:

* sea ice is water with pieces of ice in it,
* the boundary between the two regions is clear water, probably caused by winds and currents moving the floating ice away from the edge of the ice shelf.

I got the image at [Sentinel Playground](http://apps.sentinel-hub.com/sentinel-playground/#lat=-68.10712566634318/lng=-60.3424072265625/zoom=9/preset=1_NATURAL_COLOR/layers=B04,B03,B02/maxcc=100/gain=0.3/time=2015-01-01|2016-11-21) using 100% cloud filter, 0.3 gain and date selection of 2016-11-21.

EDIT: Added more info about the position, scale and orientation of the image.

> **Comments:**
> **username_1**: The location is 68.28 South, 60.47 East, and the scale is about 130m/px. North is up in the image.  
> **username_0**: OK great! The image makes much more sense to me now. Thanks! One quick question - is your image from visible light, IR, radar, or something else?  
> **username_2**: Side note: There's a distinction between sea ice and the ice of an ice shelf. The ice shelf is the extruded end of a glacier, snow and ice mounded on land over thousands of years and pushed out to sea; sea ice is the ice that has formed on top of the ocean. Sea ice is usually 1-2 meters; this region of Larsen C is about 1,100 meters thick. So there's a significant height difference for casting a shadow.  
> **username_0**: @username_2 I'm sure you are saying something illuminating but I'm not getting it. Every time I look at the image in the question, my brain tells me it's three dimensional, and the dark ribbon in the middle is a shadow. But it isn't, is it? Is the ice shelf also ~10% above the water, ~90% below?  
> **username_1**: I'm not an expert on radar sensing, but i think for a cast shadow to be visible in an image you'd need the light source direction to be different from viewing angle. Radar emits its own 'light', so unless the image has been orthorectified to change its apparent biewing angle, you won't see cast shadows on radar imagery. Also, for a couple of km long shadow on a cliff that's ~ 100m high, the illumination angle would need to be very low, definitely not consistent with sentinel-1, which i think is pointed more or less directly downwards.  
> **username_2**: Ah, now I see the question better. The black area should be open sea between the ice shelf and the sea ice. Source images can be found at http://www.polarview.aq/arctic, choose SAR Imagery then Sentinel-1: "Sea ice typically reflects more of the radar energy emitted by the sensor than the surrounding ocean, which makes it easy to distinguish between the two. But the amount and character of reflected energy are functions of the physical properties of the sea ice, which can be quite complex; thus, it can be difficult to interpret radar images of sea ice."  
> **username_0**: @username_1 Yep, of course I know you are right. It's an illusion and I'm trying to tell myself to stop seeing it. I think the fact that the area it is black in the image is what's making it seem so pronounced.  
> **username_0**: @username_2 wow that's a really handy website! OK I will have a look around and get more used to radar imagery, thanks!  

---

