The visual stratigraphy of the ice – University of Copenhagen

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Centre for Ice and Climate > Research > Drilling and analysing ice cores > Cutting and analysing ice cores > The visual stratigraph...



The visual stratigraphy of the ice

Glacier ice contains visible layers called cloudy bands. Especially in the relatively dirty glacial ice, the layers are related to the content of dust and other impurities and can be used for dating purposes.

The layers are not clearly visible in the freshly drilled ice core, as the core surface is scratched by the cutters. To record the visible layering, or the visual stratigraphy, a special tool called a line scanner is used on a section of the ice core that has been polished.

In the line scanner, a camera above the ice slab and a light source underneath the core are moved synchronously along the ice core.

Line scanner

Light is focused by the lenses and crosses the ice at a 45° angle relative to the ice surface. If there are no impurities in the ice, the light passes through the ice and does not reach the camera. These areas appear black on the image. When light is scattered by cloudy bands, bubbles, and impurities, the camera records these layers as white or grey areas.

The device

The line scanning device that records the visual stratigraphy of the ice core. The light from below is scattered by cloudy bands and bubbles and is recorded by the camera. The light sources and camera move over the 1.65 m long ice core section.

Visual statigraphy

Scanning picture from the line scanner. The whitish layers are called cloudy bands and occur because of increased dust content. The layers are more or less annual and can be used for dating purposes. The small dots are bubbles in the ice, and the black areas correspond to clear ice.

 

 

 

 

 

 

 

 

 

 

Read more about the correlation of ice crystal size and the visual layers in the ice.