Sea Ice Thickness measurements

Electromagnetic (EM) induction sounding for ice thickness measurements is a technique that can achieve long profiles of some kilometer length. This a very powerful tool that we would like to be able to use in the future.

Arctic sea ice thickness data is only sampled in very limited periods of time and the spatial coverage is also very limited. A research group at the Alfred Wegener Institute for Polar and Marine research lead by Christian Haas has therefore operationalised electromagnetic (EM) induction sounding for ice thickness measurements.

The accuracy and robustness of the EM method has been evaluated by comparing coincident drill-hole and EM measurements. To achieve long profiles of some kilometer length, the EM sensor was mounted onto a sledge and man-hauled across ice floes.

An advantage of the EM technique is that it can be deployed from helicopters or airplanes. In the summer of 2001, a new helicopterborne EM sensor ("EM-Bird") was operated in the Arctic for the first time, yielding high resolution thickness data of good quality. As a cooperation between two projects (DAMOCLES and ProClim) and four institutions (AWI, UNIS, NP and UoB) the EM-Bird was flown in Storfjorden in May 2006.

To the left the EM Bird is operated in Storfjorden by Sebastian Gerland from the Norwegian Polar Institute, May 2006. (Photo: Eric Brossier)

To be able to perform systematic large-scale studies of the ice thickness distribution we have proposed to buy another EM-Bird instrument from the AWI group. The range of helicopters vary with windspeed and work load, but a range of 200-300 km has regularly been achieved around Svalbard.

An example of EM data compared to drill measurements obtained in the summers of 1995 and 1996. The data are from the same region of the Laptev Sea, for further details plaease go to the AWI sea ice group.

The EM Bird is a heavy and big instrument, but it can measure the sea ice thickness at a speed of 100 km/h. It contains a windows computer, a GPS antenna, a laser, as well as two electromangnetic antennas (Photo: Stefan Hendricks AWI)