Virkisjökull

Iceland is one of the most volcanically active areas of Earth and has hundreds of volcanoes. About 32 systems are considered active. Most volcanoes are small, but the largest are massive enough to rise above the “snowline” and are draped in glaciers. The highest point in Iceland is Hvannadalshnúkur (2110 m) on the volcano of Öræfajökull (“wasteland glacier”). This is Iceland’s largest active volcano and being so high it is covered by glaciers. These are either short valley glaciers or piedmont (“mountain foot”) lobes. The glacier cover merges with the larger ice cap of Vatnajökull, Europe’s biggest ice cap, which covers large volcanoes to the north and west.

Virkisjökull is one of the largest of Öræfajökull’s glaciers on its southwest flank. The 3D model above shows Virkisjökull merged with its neighbour Falljökull (“falling glacier”). A well-preserved series of lateral moraines are present on the south side of the glacier, most less than 100 years old. These demonstrate that the glacier has retreated dramatically through the 20th century as a result of global warming. The recent retreat of the glacier has been studied by my colleague Jeremy Everest at the British Geological Survey. Jeremy and co-workers have set up an array of instruments around the glacier including weather stations, GPS to measure ice velocity and ablation, cameras, seismometers, and automated stream gauges. Only a handful of the many thousands of glaciers around the world are monitored closely, so this is an important project. Not only can we study the conditions surrounding rapid glacier retreat but we can also learn from the landforms left behind, such as moraines. By studying these landforms we can use the knowledge to better understand the conditions responsible for glaciation (and retreat) historically and during the last ice age.

The model of Virkisjökull was constructed using aerial photography taken in 2007 by the Natural Environment Research Council Airborne Research & Survey Facility (NERC ARSF). Monitoring such as this forms an important baseline for future studies. Firstly, there is the visual record of the state of the glacier. Secondly, stereo photography allows a 3D model to be built. Although the photography was not taken for this purpose and the coverage is uneven, with some gaps, the technology allows a surprisingly good model to be constructed. Referenced using known ground control, a digital surface model can be created which allows the surface of the glacier at the time to be measured. This highlights the value of archived imagery and scanning negatives so we can better study the past to understand the future.

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