Ice movement in the Antarctica (Stereo)

This SAR image was acquired on 11 March 1992 over the Weddel Sea in Antarctica, about 400 km east of the Antarctic Peninsula, another image of the same area has been gathered on 14 March 1992

The centre in both images is the same, 71deg 25min South, 53deg 6 min West.

The North is in direction of the upper right corner with respect to the image centre, SAR illumination is from the left. The scene is acquired entirely over sea area and therefore consists of smaller and bigger ice floes. The dark linear features are leads. Leads are narrow ice free zones created as a result of the ice movements. The slightly darker area to the right is supposed to be ice of different origin, probably recently affected by a warmer air-mass, melting the ice surface and reducing the penetration of microwaves.

By comparing both images the trend of the movement can be assessed. In 72 hours the larger ice floes have moved 22 km northwards, hence the average speed was 300m/hour.

A fascinating experiment can be made by looking at the relative movements using simple 3-D techniques. For this reason the two images are superimposed, by compensating only for the general (translation) movement and displayed in red (11 March) and cyan (14 March).

Looking at the combined image through blue (left eye) and red (right eye) glasses, a pseudo-stereo effect is evident. One needs to observe the image with the viewing axis parallel to the main ice movement to assess the relative speed of the movement along this axis: a stepwise gradient (blue lines) is obvious from a high diagonal ridge in the center to a much deeper area towards the upper left corner, etc. In order to appreciate the parallaxes in the east-west direction, the image needs to be inspected over the bottom left corner. In fact few cliffs can also be found, suggesting a slight rotational movement of the ice. Another feature showing the relative movements are the open leads (red arrows) that have changed drastically within 3 days.

ERS Data Utilization Section, ESA/ESRIN

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry