Sentinel-2A now watching Antarctica

Simon Gascoin, 6 décembre 2016

Sentinel-2A was launched on 23-July-2015 but the routine operations started in July 2016 after the ramp-up phase [1]. Now with the onset of the austral summer, the first Sentinel-2A images of Antarctica are getting available (except for Dome C, which is a calibration site).

As of today only 9 images over Pine Island glacier are available for example. However this is enough to find three cloud-free images in the glacier’s terminus area. Here I selected the images of 21-Oct-2016 and 04-Nov-2016 to run my simple glacier displacement script in Google Earth Engine (the code is here). I just increased the values of the maximum offset and the patch width because this large floating ice tongue is moving faster than San Quintin glacier.

var displacement = image2RedBand.displacement({
 referenceImage: image1RedBand,
 maxOffset: 1000.0,
 patchWidth: 5000.0,
 stiffness:5
});

Displacement map of the Pine Island glacier tongue made from two Sentinel-2A images. The offset map is shown over the natural color images but only the red band was used in the computation.

The algorithm works well since the surface features (crevasses, etc.) are well defined [2]. Also the high reflectance of the glacier surface in the visible increases the signal to noise ratio, while there is no saturation thanks to the good radiometric performances of Sentinel-2A.

[1] See https://sentinel.esa.int/web/sentinel/missions/sentinel-2/operations-ramp-up-phase

[2] Jeong et al. (2016) Accelerated ice shelf rifting and retreat at Pine Island Glacier, West Antarctica. Geophys. Res. Lett. doi:10.1002/2016GL071360 PS. I posted more Sentinel-2A images of these fascinating landscapes here, here or here… but you can explore yourself in the Sentinel Playground!

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