Diapositiva 1

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Ice motion at the Dome C ridge Luca Vittuari
DISTART University of Bologna - Italy
E-mail luca.vittuari_at_mail.ing.unibo.it
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Material
This presentation shows data and results acquired
in the framework of EPICA, ITASE, TALDICE and
VLNDEF Projects. more details can be found in
Capra. A., R. Cefalo, S. Gandolfi, G. Manzoni,
I.E. Tabacco, L. Vittuari. 2000. Surface
topography of Dome Concordia (Antarctica) from
kinematic interferential GPS and bedrock
topography. Annals of Glaciology, 30,
42-46. Geodetic and geophysical observations in
polar regions - Overview in IPY perspective,
Editors A. Capra , R. Dietrich, Springer (book
in preparation). Urbini S., Frezzotti M,
Gandolfi S., Vincent C., Scarchilli C., Vittuari
L., Fily M. Historical behaviour of Dome C and
Talos Dome (East Antractica) revealed by snow
accumulation and ice velocity measurements.
Submitted to Global and Planetary
Change. Vittuari L., C. Vincent, M. Frezzotti,
F. Mancini, S. Gandolfi, G. Bitelli, A. Capra.
(2004). Space Geodesy as a tool for measuring ice
surface velocity in the Dome C region and along
the ITASE traverse. Annals of Glaciology. vol.
39, pp. 402 - 408.
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Movements at Dome C ?
Due to
- Ice surface topography

• Glaciological hystory of the Dome behavior

• Continental drift

Measured

• Trhough integrated geodetical, geophysical
• and glaciological surveys

With respect to

• A Terrestrial Reference Frame
• (E.G. ITRF2000, ITRF2005, ..)

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Influence of ice surface topography

• Elliptical shape
• Major axis SW-NE
• Minor axis NW-SE 70 shorter
• Elongation is parallel to the prevalent wind
  direction (SW-NE)
• Snow-radar shows an increase of snow accumulation
  South-North

Contours interval 25 cm
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Influence of ice surface topography
A GPS geodetic network composed of 37 points was
established in 1995. It is composed of four
concentric rings at increasing distances from the
centre (approximately located at the drilling
site), at 3, 6, 12.5 and 25 km respectively
Surveyed twice (95/96 and 98/99)
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Influence of Ice surface topography
In order to describe relative movements, a
six-parameter similarity transformation was
applied to GPS network solutions.
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Influence of Ice surface topography
The other poles move at radial velocities of up
to 211 mm/yr 7mm/yr , with iso-values forming
concentric ellipses, similar to the contour
lines. All networks points show a vertical
velocity of about 90100mm/yr 9 mm/yr
In 1999 we estimated at EPICA drilling site,
positioned between points E10 and E14, an
interpolated relative velocity of about 15 mm/yr
10mm/yr in a N-NW mean direction between E10,
E14 302N.
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Glaciological hystory of the Dome behavior
Snowfall trajectory and its interaction with
orography is the main accumulation factor at Dome
C. Through 500 km of snow-radar profiles and
sixteen firn cores, was observed that
accumulation in the past is non symmetrical with
respect to the dome morphology.
At Talos Dome five repeatitions of GPS
measurements during last ten years have
highlighted changes in ice velocity, apparently
correlated with change in accumulation
distribution. At TD repeated GPS revealed
variations in velocities in the range -5 4
mm/yr2, while in DC this effect is unknown.
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Continental drift (I)
Absolute movement at continental scale
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Continental drift (III)
The relative motion between the Antarctic
Peninsula area and the eastern Antarctica is not
larger than 1-2 mm/yr (Dietrich et al. 2004).
So if we consider this effect as mainly induced
by a motion of the continent as a whole, the
Euler Vector computed by Nuvel-1A NNR model,
relating stable Antarctic Plate (ANTA) with
respect to ITRF2000 (Altamimi et al. 2002)
pointing out the following waited velocity at the
position of Station Concordia
Model Latitude Longitude VELOCITYmm/yr Azimuth N Vel.mm/yr E Vel.mm/yr Plate
ITRF200 75 6' 4" S 123 20' 52" E 11.42 172 -11.30 1.64 ANTA
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Movement with respect to ITRF2000 at DCRU Hor.
10.9 mm/yr 0.6 mm/yr azimuth 302 Vert. -152.6
mm/yr 1.3 mm/yr
10.9 mm/yr 0.6 mm/yr azimuth 302
The new measure carried-out at DCRU confirms the
value estimated at EPICA location in 1999 1510
mm/yr with azimuth 302
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Conclusion and outlook

• GPS measurements indicate that the DC summit move
  up to few mm/yr horizontally and up to 9-10 cm in
  vertical direction. At this level of resolution,
  absolute and relative measurements of ice surface
  velocity must be constrained to GPS long time
  series in order to reach the maximum reliability

• GPS located on the roof of the noisy building has
  proven the capability of GPS to acquire during
  the winter at Dome C, opening the possibility of
  installation of a permanent station on the
  Antarctic plateau

• To avoid local effects induced by the buildings
  structure, the GPS permanent station has to be
  designed and installed on a submerged velocity
  system coffee-can powered by Station Concordia

• To preserve the use of the GPS strain network
  installed at Dome C, extensions to network poles
  must be added before snow accumulation completely
  cover the poles heads

• In order to study the effects induced by the
  spatial variability in snow accumulation, non
  symmetric with respect to dome morphology, it is
  required a wider analysis that include repetition
  of GPS measurements on the strain network for
  long periods