DORIS DAYS 2-3 May 2000
DORIS campaigns at Dome Concordia,
Antarctica in 1993 and 1999-2000
C. Vincent1, JJ. Valette2, L. Soudarin2, JF. Crétaux3, B. Legresy3, F. Rémy3, A. Capra4
1 LGGE/CNRS,
Laboratoire de Glaciologie et de Géophysique de l’Environnement, Grenoble, France
2 CLS, Collecte Localisation Satellites, Ramonville, France
3 LEGOS/GRGS (CNES/CNRS-UPS), Toulouse, France
4 Istituto de Topografia, Geodesia e Geofisica Mineraria, Universita de Bologna
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Dome Concordia
Titre:
GMT v3.0 Document f rom grdcont our
Auteur:
legres y benoit -grgs 62956Aperç u:
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Base on the Antarctic continent
open from December to February since 1996,
permanent by 2003
Management by IFRTP
Concordia : French - Italian glaciological research project (LGGE/DISTART,...)
topics : snow accumulation, ice thickness, ice flowing …
EPICA :
European project for deep ice coring
topics : ice cap response to global climate changes,
north-south hemisphere coupling...
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Why a drilling location there?
Interests of this continental dome :
T < -25°C, no summer ice melting
excellent location for a whole Antarctic record
3300 m thickness  long and continuous climate record 400 Ka
least disturbed ice sequence at the dome summit (minimal ice flow correction)
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Main geodetic informations needed
Questions
1996 Position of the dome summit ?
Technique
ERS-1 altimeter (Rémy)
GPS (Ceffalo)
Airbone VHF radar (Tabacco) for layering
2000 Absolute 3D ice surface velocity ?
local deformation ?
C. VINCENT LGGE/CNRS
DORIS 1993 and 1999-2000 (C. Vincent)
GPS 1995-1998 (A. Capra)
ERS-1 Insar 1996 (B. Legrésy)
DORIS DAYS 2-3 May 2000 Toulouse, France.
Charming but constraining place (1)
Equipment suffering :
beacon specification
from -20° to +55°C
gradient < 10°/hr
Generator failures  USO drift of a few 10-11/jr
(still under specification)
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Charming but constraining place (2)
Scientist suffering :
Dry but freezing summertime
(4 g/cm2 equivalent water a year)
What geodetic « monumentation » ?
How to prevent from stake subsidence?
How to measure snow accumulation ?
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
CLS DORIS Data Processing Center, Toulouse
Onboard instrument control
Telemetry acquisition and preprocessing
Operational orbit and stations position (48 h delay)
2 days delay Dome C operational location (height)
Spot 4 data validation
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
DORIS campaigns
10 km
5 m isolines
 Drilling site
D1 Doris main site (IERS id. : 66009 in 93 - 66013 in 99)
D2 Doris ancillary site (66014)
DORIS observations
at main point (D1)
C. VINCENT LGGE/CNRS
1993 : 16 days (11/26 – 12/5)
SPOT 2
85 pass. / 2097 obs.
1999-2000 : 27 days (12/8 – 1 /2)
SPOT 2 and 4
498 pass./ 13164 obs.
DORIS DAYS 2-3 May 2000 Toulouse, France.
Data processing
At GRGS/CLS DORIS data analysis center for IERS and IDS
with GINS/DYNAMO software
and the most recent models : GRIM5 (Biancale et al.), atmospheric effects
Geodetic parameters
: satellites orbit, stations position and velocity
Empirical coefficients
: air drag, solar pressure radiation, Hill residual forces,
zenital tropospheric delay
Instrumental parameters
: USO frequency bias
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Absolute velocity corrections
Antarctic plate tectonic motion deduced from DORIS at Dome Concordia :
in latitude
: -9.4 mm/yr
in longitude
:
0.4 mm/yr
Titre:
GMT v3.0 Document from ps coas t
Auteur:
laurent s oudarin grgs p 62925
Aperç u:
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avec un aperç u intégré.
Commentaires:
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un autre type d'imprimante.
(Crétaux et al. 1998)
Post glacial rebound uplift : less than 1-3 mm/yr
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Preliminary DORIS results
2 months global network solutions (Nov-Dec 93 and 99)
Typical precision :
Permanent station
1 satellite
2 cm
2 satellites
1 cm
Dome C
3 cm (1993)
1.5 cm (1999)
7 parameters Helmert transformation (versus solution 1993)
3D coordinates changes over 6 years
(same réf. point, plate motion is removed)
C. VINCENT LGGE/CNRS
Latitude
Longitude
Height
- 3.6 cm
- 10.8 cm
-57.4 cm
DORIS DAYS 2-3 May 2000 Toulouse, France.
Contribution to ice core analysis (1)
DORIS 3D absolute velocity gives an input for numerical ice flow
model in depth. Essential for cores dating.
DORIS results in horizontal :
0.6 cm/yr in latitude
-1.8 cm/yr in longitude
Titre:
GMT v3.0 Doc ument from ps basemap
Auteur:
legresy benoit -grgs 62956Aperçu:
Cette image EPS n'a pas été enregis trée
av ec un aperçu intégré.
Commentaires :
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imprimante Pos tSc ript mais pas sur
un autre ty pe d'imprimante.
agree with
balance model between
snow accumulation and
ice flow induced by gravity
(figure)
(Legresy)
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Contribution to ice core analysis (2)
 DORIS results in vertical : -9.6 cm/yr
Probably the first absolute determination of the vertical velocity
 observed snow accumulation at the top of the stake (height level change) :
35 cm over the 6 years while 10 cm/yr is expected (Petit et al.)
Error observation or snowfall anomaly ?

Mass balance between snowfall and ice flow towards the ocean ?
Sea level and climat changes implications
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Contribution to radar remote sensing observations
SAR Interferometry maps relative surface velocity in the line of sight
ERS SAR interferogram (69 days interval) shows maximum of 3 cm/yr
DORIS gives the absolute ITRF tie of the velocity fields
Space Radar Altimetry maps ice topography within 10-20 cm
but an in-situ calibration is needed,
moreover the signal penetration depends on the snow structure
DORIS gives the height reference and its variations in time
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.
Conclusions
 DORIS (93-99) component of CONCORDIA project confirms that a very low
absolute horizontal ice surface velocity affects the EPICA drilling (< 2 cm/yr).
Also vertical flow determination as a first.
 DORIS absolute geodetic approach fully completes GPS survey and
calibrates radar satellite remote sensing techniques (with future missions
ERS2, ENVISAT, IceSat, CRYOSAT).

Proposal to IDS for repeated DORIS campaigns at Dome Concordia
C. VINCENT LGGE/CNRS
DORIS DAYS 2-3 May 2000 Toulouse, France.