Radio-echo sounding measurements

Systematic mapping of the bedrock beneath Vatnajökull by radio-echo sounding measurements began in 1980. The radio-echo sounding device is hauled with a snowmobile or snow sledge to measure continuous profiles of reflected radio waves. The travel time of the wave reflected from the glacier bed is recorded and from this the ice thick¬ness can be calculated. Altogether, approximately 10,000 km of profiles have been measured, with 200−1000 m average spacing on the ice cap. Point measurements have also been done on foot in areas where motorised vehicles cannot be used, for example in heavily crevassed areas and on the outlet glaciers of Öræfajökull. Maps of the subglacial topography have been produced by interpolation of the radio-echo sounding profiles. The high-resolution maps show previously unknown landscapes and formations including the geometry and location of volcanic systems, the possible routes of jökulhlaups, and catchment basins of glacier rivers. Deep troughs and high plateaus are hidden under the ice surface and many of the southern outlet glaciers have carved deep valleys, reaching up to 260 m below sea level.

 

Radio-echo sounding measurements in Grímsvötn. Photo: Snævarr Guðmundsson, 2012.

Radio-echo sounding measurements in Grímsvötn. Photo: Snævarr Guðmundsson, 2012.

 

Radio-echo sounding measurements. Photo: Ágúst Þór Gunnlaugsson.

 Radio-echo sounding measurements on Dyngjujökull. Photo: Ágúst Þór Gunnlaugsson, 2015.

 

Glacier extent and ice-surface maps

The glacier extent at different times since the end of the Little Ice Age has been delineated from glacial geomorphological formations, maps, aerial images and remote sensing data. Glacier surface maps from different times are available, including high-resolu¬tion digital elevation models (DEMs) from lidar and satellite measurements. The maps provide information about changes in ice surface geometry and they allow delineation of ice cauldrons and ice-flow basins. The maps are, furthermore, useful for studies of jökulhlaups, mapping of crevasses and they have revolutionised studies of glacier changes.

 

Outline of Vatnajökull ca 1890 and 2010. Source: Icelandic Meteorological Office and Institute of Earth Sciences.

Outline of Vatnajökull ca 1890 and 2010. Source: Icelandic Meteorological Office and Institute of Earth Sciences.

 

Outline of Öræfajökull outlet glaciers 1890 to 2014. Source: Vatnajökull National Park 2017.

Outline of Öræfajökull outlet glaciers 1890 to 2014. Source: Vatnajökull National Park 2017.

 

Surface map of Skálafellsjökull, Heinabergsjökull and Fláajökull outlet glaciers ca 1890 and 2010. Source: Hannesdóttir (2014).

Surface map of Skálafellsjökull, Heinabergsjökull and Fláajökull outlet glaciers ca 1890 and 2010. Source: Hannesdóttir (2014).