The Svartisen ice caps (1359' E; 6640' N, 221 km² and 148 km²) are situated in a maritime climate close to the Atlantic Coast in Nordland, Northern Norway. With a total area of 369 km², this is the second largest ice mass in Norway. The altitudinal range is from 7 to 1600 m a.s.l. Annual precipitation in the area is more than 2000 mm along the coast declining rapidly inland to less than 1000 mm on the eastern side of East Svartisen. In recent years several outlet glaciers of West Svartisen have experienced advances of the front position (indicating that the glacier has a positive mass balance and is growing) whereas several outlet glaciers from East Svartisen have experienced retreats over the same period.

Map of the Svartisen ice caps (Norway).

West Svartisen and East Svartisen have a range of glaciological data going back almost a century, such as changes in front position of two of the outlet glaciers of West Svartisen (Engabreen and Fondalsbreen) back to 1903 and 1906 respectively as well as meteorological data from a nearby meteorological station (Glomfjord) going back to 1920. Apart from changes in front position, the glaciological data includes mass balance measurements on Engabreen since 1970, as well as mass balance measurements on several of the other outlet glaciers and smaller glaciers for shorter periods, such as Storglombreen, which has an area of 60 km² and Svartisheibreen. There is aerial photography for the whole of Svartisen from 1968, 1985 and 2002, and other aerial photography exists for individual glaciers. Additional data sets include bottom topography for West Svartisen and front position maps from several outlets of East Svartisen.

Shaded relief of the Svartisen ice caps DEM. The DEM has a resolution of 25 m, and is geocoded in UTM zone 33N. The topographic-related interferometric phase was simulated from this external DEM and removed from interferograms to isolate the displacement related phase. The image to the right shows simulated SAR amplitude image in SAR range-doppler co-ordinates, generated from the DEM.

The map opposite indicates the locations of GPS velocity measurements. These are useful for comparison with velocities derived from InSAR or other remote sensing techniques.The smaller map below shows base station locations used for differential correction of GPS position measurements.

Repeated field observations by NVE using differential GPS stake position measurements reveal temporal velocity variations. These are believed to be caused by:

variations in local water pressure, affecting sliding

variations in thickness of snowpack

processes in the till (not relevant on Engabreen)

The figure opposite demonstrates Winter and Summer horizontal stake velocities over Engabreen.

Repeat Photogrammetry allows for elevation change detection and velocity extraction see velocity map to Right.

Slow part at bend also coincides with shallow part of glacier. The black-filled contour represents a velocity of 60 cm/day, other contour lines at 20 and 40 cm/day.

Landsat 7 ETM imagery from 7th September 1999 (left) and 3rd August 2004 (right). Repeat acquisitions of Satellite imagery allow for analysis of (e.g.) margin changes, surface condition (melting, ice facies, etc.).

ERS-1 SAR data in slant-range SAR co-ordinates from orbit 23592, frame 1341 of Svartisen, 18th January 1996. The table below, shows the InSAR pairs available to the project from processing of ERS-1/2 SAR data. Scenes listed in bolded red were used in the production of 3-dimensional surface displacement map from dual-azimuth interferometry:

N/A

Above: Flattened, filtered, geocoded differential interferogram of March 28 and 29, 1996. Look direction (ascending mode) is indicated by the arrow (incidence angle ~23), the perpendicular baseline is 10 m.

Line-of-sight surface displacement map of the Svartisen ice caps in map geometry for March 28 and 29, 1996.

Above: Flattened, filtered, geocoded differential interferogram of April 1 and 2, 1996. Look direction (descending mode) is indicated by the arrow (incidence angle ~23), the perpendicular baseline is 57 m.

Line-of-sight surface displacement map of the Svartisen ice caps in map geometry for April 1 and 2, 1996.

3-dimensional velocity map for the Svartisen ice caps derived from dual-azimuth interferometry, using the ERS SAR Tandem data of March 28 and 29, 1996 (ascending orbit) and April 1 and 2, 1996 (descending orbit). Displacement along the surface normal of the DEM, filtered with an averaged distance of about 1250 m in order to reduce local effects, was assumed. In the velocity final map, presented left, areas with unstable solution related to the angle of 48 between observations in ascending and descending mode, where masked. Over the Svartisen ice caps maximum velocities of more than 30 cm/day were measured during winter, 1996.

Click on chips opposite to see enlarged sections in a new window.

The figure opposite shows a comparison between dGPS- and InSAR-derived velocities. Differences between the two may be explained by:

different seasons being measured by each technique

different glacier regimes being measured - +ve mass balance in 1996 at time of SAR aquisition, versus -ve balance over the last five years

InSAR measurement errors

Vertical vs. Horizontal velocities being measured

Combination of InSAR-derived displacement data with cartographic and other data sources allows for further generation of value-added products for end-users. Shown left, are two examples of such products illustrating the glacier rheology of the Svartisen Ice Caps click on either image to open a larger version in a new window.