12. September 2008

Successful field work in Finnmark and Troms, Northern Norway 2008

Contact person for additional information: Hanne H. Christiansen

Text and photos by Etzelmüller, Bernd,University of Oslo

Between 27.7. and 7.8. field work was carried out for the Norwegian TSP project. All boreholes drilled and instrumented in 2007 were read out, and an extensive number of geophysical soundings were done. The work was carried out  in co-operation with the Norwegian Geological Survey (NGU), the Universities of Karlsruhe (Prof. Christian Hauck)  and Jena (Christin Hilbich), Germany, and the University of Ottawa, Canada (Prof. A. Lewkowicz).

Ground temperatures:

The sites in Lavkavagge/Troms and Iskoras/Finnmark show that the lower boundary of mountain permafrost is close to these borehole location elevation.  The bore hole temperature monitoring allows us now to follow the ground temperature development as response to climate change.  In addition to ground temperatures, air and surface temperatures are monitored along a north-south transect over the Iskoras mountain. This will give valuable information about air temperature inversions and snow conditions.

Ground temperatures at Lavkavagge, northern Troms, 750 m a.s.l. The borehole is probably still not in equilibrium after drilling operation. However, there are clear evidence of shallow permafrost in the bore hole as expected. The right illustration shows a 2D-plot of temperature-depth development in the borehole between June and August 2008.

Ground temperatures at Kistefjellet, southern Troms, 1000  m a.s.l. This borehole is covered by a thick snow cover during winter, and shows seasonal frost down to c. 4 m depth. Note that the winter temperature close to the surface never remains below -5 oC. Even if summer is cool, permafrost cannot develop at this site under present climatic conditions. However, during cooler periods of the last century and during the Little ice age, permafrost was possible at this site, as indicated by decreasing temperatures with depth. Former  ground surface temperatures will be evaluated applying transient heat-flow models. Locations without or only a little snow cover certainly develop permafrost at this site, which is also indicated by geophysical investigations.

Ground temperatures at Iskoras, Finnmark, 600 m a.s.l. The borehole indicate permafrost condition, shallow and very close to 0oC. Snow cover is very low at this site, and thus marginal to permafrost. We expect heavy winter inversion at this site, as the Iskoras meteo data clearly show warmer winter temperatures than in the nearby valley of Karasjok. This is further investigated by a monitoring program for air and ground surface temperatures along a north-south transect in the area (Picture  lower right, with PhD-stud Karianne Lilleøren, UiO, and Prof. Antoni Lewkowicz, University of Ottawa, Canada).

Geophysical soundings:

Geophysical soundings help to determine ground properties and possible variations of ice content in the ground along profile lines. We used DC resistivity tomography and seismic tomography. The NGU also measured a 2 km long profile over the Iskoras mountain along a north-south transect.  These data are now under processing.

Christian Hauck, University of Karslruhe/University of Fribourg, Switzerland , performing seismic investigations. The signal is triggered using a heavy sledge hammer. Kistefjell, southern Troms .

The diagrams above show first processing results of the DC resistivity tomography. The upper diagram is a 2 km long profile with 10 m electrode spacing, while the inlet profile  shows a 250 m long profile with 2 m electrode spacing. Blue areas are high resistivities and either bedrock or permafrost. These resistivities will be combined with seismic velocities, to determine the possible amount of solid material, ice, water and air along the profile.