The Tweeting Ice Shelf: geophysics

and outreachBrice Van Liefferinge, Reinhard Drews, Sophie Berger, and Frank PattynUniversité Libre de Bruxelles, Laboratoire de Glaciologie, Brussels, Belgium (bvlieffe@ulb.ac.be ; @bvlieffe)

http://tweetiniceshelf.blogspot.com/ https://twitter.com/TweetinIceShelf

The project

First results

Tweets Ref. and ressources

Field season / installation

Run with us

Choose one

Project’s description• Aims:

To continuously monitor horizontal motion of a well-studied ice shelf in Dronning Maud Land (Antarctica) using GPS.

To investigate a subglacial channel observable at the surface (see installation) : how does the trench behave ? How does it move? Does it widen? Does it enhance the ice flow? Is there active melting under the shelf?

CdS GPS CGEO GPSpRES

Project’s description• Aims:

To carefully map ice shelf flow speed in order to determine the mass balance of this ice shelf.

To broadcast the measurements to the Brussels office (ULB) on a daily basis over the course of one year.

Take part of a larger network using e.g. pRES measurements (Pattyn et al., 2012; Drews et al., 2015 ; Callens et al., 2014).

To monitor the real-time positioning and changes.

To inform a larger community of interest via an outreach program using Twitter.

@TweetinIceShelf

Field season / installationThe Tweeting ice shelf components were installed in December 2014 on the Roi Baudouin ice shelf (Dronning Maud Land, East Antarctica)

Field season / installation Three GPS systems were deployed, two on the flanks and one within

the trench (see here). The ones on the flanks are basic GPS systems that record there position every hour. They are called GPS CGEO (from Cercle de Géographie et de Géologie de l'ULB) and GPS CdS (from Cercle des Sciences).

Science / installation• Ice shelves are complex : several longitudinal depressions

(trenches) stretch from the southeast to the northwest along which the ice shelf fractures close to the ocean front. These depressions in the shelf are 15m lower than the surrounding surface of the ice shelf.

R.Drews, 2015, TCD

Science / installation Archimedes teaches us that the ice thickness in these hollows is

significantly lower than elsewhere. Radar measurements show that these hollows are deeply incised under the ice shelf (150 m for an ice shelf with a mean thickness of 300 m) (R.Drews, 2015, TCD)

R.Drews, 2015, TCD

300m 150m

First results To determine the mass budget of ice

shelves, we need to carefully map the flow speed !

Horizontal flowfield from interferometry measurement (S. Berger)

First results CdS GPS moved of 93.9271m in 118.5 days

289 m/yr CGEO GPS moved of 99.122m in 118.5 days

305m/yr

First results CdS GPS moved of 93.9271m in 118.5 days

289 m/yr CGEO GPS moved of 99.122m in 118.5 days

305m/yr pRES GPS moved of 85. 44m in 114 days

First results I’m dancing but why ?

satellite orbit Tide effect

In blue: measured position, in red : smoothed data

First results Are there some relations to tides ?

Padman Tide Model

First results

Frequency components of the signals

fft: Sampling frequency of 1

Signal of 12 and 24 hr

First results Are the GPSes converging into the

channel ? Too early to be affirmative, but we see a

convergence of 1° ! Are the GPS accelerating ?

The Roi Baudouin ice shelf calved a huge iceberg in January but we can’t see a modification of the velocity !

The ‘signal’ from CdS is more perturbed.

First results My sensor temperature (from the pRES) !

Two warm events It could play a role in the signal perturbation

(sinking of installation masts)

Tweets• Every week I send the locations of my GPS

and new results !

• You can follow and interact with me on @TweetinIceShelf !!

Run with us : Project supported by the “10 km of the ULB” !

Event organized every year by the students of the Faculty of Sciences of the ULB.

Collect funds to support research projects at the ULB The 26th of April, RUN WITH The Laboratory of

Glaciology of Brussels to continue the adventure !

Ref. and ressources• Drews, R.; Evolution of ice-shelf channels in Antarctic ice shelves, The Cryosphere Discuss., 9,

1603-1631, doi:10.5194/tcd-9-1603-2015, 2015.• Ahlstrøm, A. P., Andersen, S. B., Andersen, M. L., Machguth, H., Nick, F. M., Joughin, I.,

Reijmer, C. H., van de Wal, R. S. W., Merryman Boncori, J. P., Box, J. E., Citterio, M., van As, D., Fausto, R. S., and Hubbard, A.; Seasonal velocities of eight major marine-terminating outlet glaciers of the Greenland ice sheet from continuous in situ GPS instruments, Earth Syst. Sci. Data, 5, 277-287, doi:10.5194/essd-5-277-2013, 2013.

• Dunse, T., Schuler, T. V., Hagen, J. O., and Reijmer, C. H.; Seasonal speed-up of two outlet glaciers of Austfonna, Svalbard, inferred from continuous GPS measurements, The Cryosphere, 6, 453-466, doi:10.5194/tc-6-453-2012, 2012.

• Callens, D., Matsuoka, K., Steinhage, D., Smith, B., Witrant, E., and Pattyn, F.; Transition of flow regime along a marine-terminating outlet glacier in East Antarctica, The Cryosphere, 8, 867-875, doi:10.5194/tc-8-867-2014, 2014.

• Pattyn F., K. Matsuoka, H. Conway, D. Callens, M. Depoorter, D. Docquier, B. Hubbard, D. Samyn, JL. Tison; Radar and ice-core evidence for active ice-ocean interaction under the Roi Baudouin Ice Shelf, East Antarctica. J.Geophys. Res.117, F04008, doi:10.1029/2011JF002154, 2012

The tweeting Ice shelf Thanks…

The “Cercle des Sciences” and the Faculty of Sciences of ULB who co-sponsored the project.(@ULBSciences)

Jan Lenarts who provides information about the health of the ice shelf (gain of mass, melting, …) and the great moments shared in the field. (@lenaertsjan)

David Jones for the support from the British Antarctic Survey, BAS (David Jones).

IPF and PES for the field support during the installation ! ( @PolarFoundation and @AntarcticBase)