High Antarctic Plateau, Dome C, Base of Concordia - (DMC)

Instruments

Recording

INTERMAGNET

Key dates

History

The Dome C site was selected in 1974 to start research activities under the framework of the International Glaciology Project (IAGP). A shallow coring, joint French/American program was conducted at the beginning of the 1980th’s with the support of the National Science Foundation. The camp was abandoned after the end of the coring (to a depth of about 900m), which was hampered by three aircraft crashes.
At the beginning of the 1990th’s a French Italian venture planned to build up a permanent scientific base. The DomeC
site was chosen again, mainly because of the thickness of the ice cap and the low atmospheric water vapour content. The first remarkable activity was a long ice core drilling, which should help deciphering the past climate of our planet over a large time span. The coring lasted from 1997 to 2005 with the aim at drilling through the whole ice cap. The Dome C/Concordia magnetic observatory was installed in 2004, the first winterer took place in 2005.

The magnetic observatory of Dome C/Concordia comprises two huts set up on the ice-shelf, a few hundred metres away
from  the residential quarters of the base. One of the huts houses the absolute pier while the other one houses the acquisition system above the variometer cellar.

DMC is the second absolute observatory located in the inland of Antarctica, after Vostok, not influenced by coast effects and crustal field contamination. It is located inside the Polar Cap, not far away from the footprint of the polar cusp, which is the location of the field lines directly connected to the boundary of the magnetosphere. The quadrilateral, build up by the observatories of Dumont d’Urville, Terra Nova Bay, Scott Base and Concordia, is 1 000 km wide.

Since January 9th 2009, new 1Hz Acquisitions Systems (M.A.R.Cell 1.0- Magnetic Acquisition and Recording Cell 1.0) were installed at DMC magnetic observatory.

Absolute Measurements

Absolute measurements are performed on average every three days using the Declination-Inclination magnetometer DI-flux Bartington MAG01H. This D-I flux is based on a Zeiss 010B  non-magnetic theodolite fitted with a single axis sensor mounted on the telescope. D and I are measured. Total field measurements are performed every 10 seconds with a proton Overhauser magnetometer GEOMAG SM90R. The accuracy of the absolute determinations is estimated 2 nT for X,Y Z, and 0.2 nT for F.

Variometers

The fluxgate variometer (DMI model FGE - suspended three-component fluxgate variometer, Arctic model specially designed for low temperatures) and an overhauser effect proton scalar magnetometer (GEOMAG SM90R) get their sensors placed in the cellar of 2m3 inside the ice beneath the variometer shelter (Annual mean of the air's cellar temperature : -42 deg.C.) while their electronics are placed in the shelter above (Annual mean temperature of the shelter : +10 deg.C.). The internal variometer sensor temperature stays above its critical failure temperature of -50 deg.C. The triaxial variometer has a nominal output of 2.5 mV/nT and a dynamic of +/- 2000 nT. The long-term stability of the triaxial variometer is better than 1nT/month.

Accuracy of data

The adopted baseline values are calculated by spline smoothing. The uncertainty in the adopted baseline values, as well in the final 1-minute values, is estimated to be less than 2 nT for all elements.

Reference of the data

Detailed description of the instrumentation and method of data reduction are given in the annual bulletin of the Bureau Central de Magnetisme Terrestre (B.C.M.T., Paris).