How to record

high quality data on moving ice shelf? – The geomagnetic observatory

at Neumayer Station III, Antarctica

Jürgen Matzka (1), Tanja Fromm (2), Alfons Eckstaller

(2), Jölund Asseng (2), Achim Morschhauser (1), Markus Schiffler


1 GFZ German

Research Centre for Geosciences, 14473 Potsdam, Germany 2 AWI

Alfred-Wegener-Institut, 27515 Bremerhaven, Germany 3 Leibniz-Institut

für Photonische Technologien (IPHT) Jena e.V., 07745 Jena,



VNA (IAGA code) is the geomagnetic

observatory of the German Antarctic research station Neumayer III

located on the Ekström ice shelf at 70.7° S and 351.7° E. The

station is the currently the only permanent station in Antarctica

situated on an ice shelf and as such it raises unique challenges for

geomagnetic data acquisition. The station, along with the ice shelf,

drifts by 157 m per year to the north and rotates clockwise by 0.25°

per year. But high-quality, absolutely calibrated geomagnetic field

vector data depend on precise knowledge of the geodetic reference

frame and – for the study of secular variation – stable

conditions, especially with respect to artificial or crustal fields at

the observatory.

Here, we present the observatory and our approach to compensate for

the observatory's movements for obtaining both near real-time and

definitive geomagnetic observatory data.

First, the azimuth of the azimuth mark has to be determined and

updated regularly, as it also rotates with the ice. The observatory is

located in an underground ice cave and therefore celestial objects

cannot serve as a fixed reference and instead, the azimuth is

determined on a monthly basis by a north-seeking gyro.

Second, due to its northward drift, the observatory is moving across a

significant gradient of the crustal magnetic field observed first in

aeromagnetic surveys over the region as well as in ground profiles of

total field strength along the drift path. This results in a temporal

change of the crustal bias of approx. 10 nT per year. Based on the

observatory data alone, this signal cannot be separated from the

secular variation of the core field. In order to correct the

observatory time series for this change in crustal bias, vector

absolute measurements were performed along the drift path in austral

summer 2016/2017. Additionally, the aeromagnetic data was downward

continued to obtain the vector field along the drift path of the


In the austral summer 2017/18, the observatory was extended by a high

frequency induction-coil magnetometer to study ultra low frequency

waves associated with interaction of solar wind and the magneto- and