1. The Tweeting Ice Shelf: geophysics and outreach Brice Van Liefferinge, Reinhard Drews, Sophie Berger, and Frank Pattyn Université Libre de Bruxelles, Laboratoire de Glaciologie, Brussels, Belgium (bvlieffe@ulb.ac.be ; @bvlieffe) http://tweetiniceshelf.blogspot.com/https://twitter.com/TweetinIceShelf

2. The project First results TweetsRef. and ressources Field season / installation Run with us Choose one

3. 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?see installation CdS GPSCGEO GPS pRES

4. 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 @TweetinIceShelf

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

6. 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).see here

7. 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

8. 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

9. 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)

10. 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

11. 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

12. First results  I’m dancing but why ?  satellite orbit  Tide effect  In blue: measured position, in red : smoothed data

13. First results  Are there some relations to tides ?  Padman Tide Model

14. First results  Frequency components of the signals  fft: Sampling frequency of 1  Signal of 12 and 24 hr

15. 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.

16. First results  My sensor temperature (from the pRES) !  Two warm events  It could play a role in the signal perturbation (sinking of installation masts)

17. Tweets Every week I send the locations of my GPS and new results ! You can follow and interact with me on @TweetinIceShelf !! You can follow and interact with me on @TweetinIceShelf !!@TweetinIceShelf

18. Run with us :  Project supported by the “10 km of the ULB” !“10 km of the ULB  Event organized every year by the students of the Faculty of Sciences of the ULB.Faculty of Sciences  Collect funds to support research projects at the ULB  The 26 th of April, RUN WITH The Laboratory of Glaciology of Brussels to continue the adventure !

19. 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

20. The tweeting Ice shelf Thanks…  The “Cercle des Sciences” and the Faculty of Sciences of ULB who co-sponsored the project.(@ULBSciences)@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) Jan Lenarts @lenaertsjan  David Jones for the support from the British Antarctic Survey, BAS (David Jones).BAS (David Jones)  IPF and PES for the field support during the installation ! ( @PolarFoundation and @AntarcticBase)@PolarFoundation@AntarcticBase