CRACICE (Cooperative Research into Antarctic Calving and Icebergs Evolution)
Benoît Legrésy, Lydie Lescarmontier, Sara fleury , Fernando Nino, Pascal Lacroix, Laurent Testut., Clément Mayet LEGOS Richard Coleman, Neal Young, Robert Massom, Roland Warner, Andrew Meijers et Steve Rintoul David Smith ACE-CRC, CSIRO-CMAR, AAD Ben Galton-Fenzi ACE-CRC Hobart (postdoc in toulouse planned) + Laurent Besnard (Stage M2R) +I.E. Tabacco. Univ. Milan + D. Blankenship, D. Young, Univ Texas ÆA project started since Oct. 2007 objectives : To follow the calving event of the Mertz Glacier and the evolution of Ninnis glacier and Cook ice shelf tributaries with 3 aspects : - fieldwork -Satellite observations - modelling Field work organised within the french polar expeditions IPEV. GPS beacons on the glacier and surrounding rock sites. Support from CNRS, INSU, CNES, + image providers ESA, NOAA, NASA, CNES SPOT, …
Part attached to the glacier
Part future iceberg
Survey using autonomous precise GPS beacons
100 km N
Questions of interest motivating our scientific studies • Ice: Deformation, flow, rifting, calving Variations in time (variability, reaction to calving)
• Ocean-Ice : Mechanical Tides, currents, swell, wave, lubrication Thermodynamic Melting/freezing, mélange, penetration in crevasses.. Ocean = heat source and transporter, mechanic forcing Ice = fresh water source bathymetric obstacle, mechanical energy dissipator, heat sink
ROMS modelling (B. Galton-Fenzi et al.)
About thermodynamic ocean-ice exchange
ROMS modelling (B. Galton-Fenzi et al.)
ROMS modelling (B. Galton-Fenzi et al.)
TUGO modelling (C. Mayet, L. Testut al.)
About mechanic ocean-ice exchange Bathymetric effect push pulls on the ice tongue.
GPS results
12 cm/d
opening
Tidal modulation : +/- 5 cm/jour Mainly along flow 3m/d Tidal modulation : +/- 10 cm/d
25 km
Tidal modulation : +/- 10 cm/d Lateral movement
Legresy et al. 2010, Lescarmontier et al., 2010, Massom et al. 2010.
Tides and currents influnce the ice flow very significantly (Legrésy et al., 2004) and reveals to be a major driver of the calving.
1 order of magnitude in GPS processing accuracy leads to the detection of fine vibrations of the ice tongue (Lescarmontier et al., 2010)
SCRS-PPP
GINS-PPP (CNES-GRGS)
Lescarmontier et al., 2010
The Mertz glacier Tongue calving event of February 2010 seen by ENVISAT ASAR Supporting material include : -A series of ASAR radar images from the ENVISAT satellite (ESA) to illustrate the calving event over the last month
ASAR 06/02/2010
ASAR 07/02/2010
ASAR 10/02/2010
ASAR 13/02/2010
ASAR 16/02/2010
ASAR 19/02/2010
ASAR 20/02/2010
ASAR 22/02/2010
ASAR 23/02/2010
ASAR 25/02/2010
ASAR 26/02/2010
ASAR 01/03/2010
ASAR 04/03/2010
ASAR 10/03/2010
ASAR 14/03/2010
ASAR 17/03/2010
ASAR 26/03/2010
ASAR 01/04/2010
ASAR 11/04/2010
SPOT-DEM (SPIRIT)+ SPOT HRG *Evolution of the crac and the iceberg + Icesat + Envisat-RA2 *Measure the deformation with repeat images + ASAR + MODIS + LANDSAT thanks to the high resolution *DEM to Improve the ocean geometry knowledge
+ several acquisitions in the last 2 months
waiting for isis to get the data …
STD tends to be around 10m when ERS is reliable, better with V2 (inland), courtesy D. Smith (AAD Australian Antarctic Data Center)
It would be convenient to not use a geoid but better an ellipsoid if possible The geoid is very significantly spatially varying in the area
Corrected for tides Very significant trends of the geoid ~ 4cm/km 1.0m std
Icesat & Envisat compare well, 1m bias at the Xover Different seaice condition, snow over seaice,…
The large scale topo suits well to the radar profile. The ratio leads to density of 0.86 +- 0.02 A snow thickness of 8+-3% of the total thickness
Not always systematic link between correlation level and DEM quality
Conclusion : * Over the continent where not so much detail is available (but a bit) the quality of the SPIRIT DEM is quite good. * Over Seaice, it is totally unreliable (may be worth masking). * Over the ice tongue, the quality is uneven. It shows really good agreements within few meters and nice features reproduced whle in other places very bad values over 50m out appear. The cc is an indicator and is not an easy flag. ? Process, radiometric quality, inclusion of ancillary data into the processing? Can we get the original images to try out making the DEM ourselves?
