Deux gros glaçons quittent l'Antarctique

L'Antarctique sort à peine de sa torpeur hivernale que déjà deux évènements majeurs viennent de se produire sous l’œil de Sentinel-1.
 
Le 12 juillet dernier, une crevasse géante à fendu la barrière de glace Larsen C [1], mais il a fallu attendre que la banquise desserre son étau en septembre pour que l'iceberg A68 commence à dériver. Ce glaçon couvre une superficie de 5800 km² (les deux tiers de la Corse).
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Vavilov Glacier in 2016 and 2017

Back from a long summer break, I needed to find something else to do than just catching up with emails... Luckily, the organizers of the 2017 International Glaciology Society meeting in Boulder tweeted this animation of the Vavilov Glacier (October Revolution Island, Russian Arctic):


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Pine Island Glacier rift

The rift of Pine Island Glacier's floating tongue is a cause of concern among glaciologists because it suggests that this part of the ice shelf is not stable and may collapse in the future. As explained in this EOS article [1]

Rifts usually form at the sides of an ice shelf where the ice is thin and subject to shearing that rips it apart. But this particular rift originated in the center of Pine Island Glacier’s ice shelf and propagated out to the margins.This implies that something weakened the center of the ice shelf. The most likely explanation is that a crevasse melted out at the bedrock level, driven by a warming ocean, according to the researchers."

Online survey: can we detect an expansion of the rift on the Sentinel-2 images only?

Sentinel-2 images of the Pine Island Glacier ice shelf rift. Each subset shows the eastern portion of the rift on a different date. Which one shows the longest rift according to you? Click on the image to vote!

 

The results of the survey are given in the next post.

 

[1] Lipuma, L. (2017), West Antarctic ice shelf breaking up from the inside out, Eos, 98, doi:10.1029/2017EO064743. Published on 04 January 2017

3D views of Aru Co avalanches from Pléiades stereo imagery

A Pléiades stereo pair has been acquired on 2016-Oct-01 just a few days after the second glacier collapse in the Aru mountains. The panchromatic band has 0.5 m resolution, which allowed us to generate a post-event digital elevation model of the area. From this digital elevation model and the Pléiades 2 m multispectral imagery, Etienne Berthier generated these stunning 3D views of the aftermath...

Preliminary estimates of the volume detached from the glaciers are 66 Mm3 (first, north one) 83 Mm3 (second, southern one).

Patagonian skies are not cloudy anymore

"The most usual weather in these latitudes is a fresh wind between north west and south west with a cloudy overcast sky" - Phillip Parker King, Sailing Directions for the Coasts of Eastern and Western Patagonia (1832).

 

Patagonia is a beautiful place to visit but campers know that the weather is extremely variable and the sky is often cloudy. This can be a problem for glaciologists, too, since they rely on optical satellite imagery to study glacier area changes over the last decades (mainly Landsat). Clear-sky optical images can also be used to determine glacier velocity, albedo, front variations, etc.
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