Visual stratigraphy of the North Greenland Ice Core Project (NorthGRIP) ice core during the last glacial period

• Published in: Journal of Geophysical Research
• Main Authors: Svensson, Anders, Nielsen, Søren Wedel, Kipfstuhl, Sepp, Johnsen, Sigfus J., Steffensen, Jørgen Peder, Bigler, Matthias, Ruth, Urs, Röthlisberger, Regine
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2005
• Subjects: 580 Plants (Botany); 530 Physics; Greenland; Greenland ice core; Greenland Ice core Project; ice core; North Greenland; North Greenland Ice Core Project
• Online Access: https://boris.unibe.ch/158304/1/svensson05jgr.pdf; https://boris.unibe.ch/158304/

A continuous high-resolution record of digital images has been obtained from the North Greenland Ice Core Project (NorthGRIP) ice core (75.1°N, 42.3°W) in the depth interval from 1330 m to the bedrock at 3085 m. The ice core stratigraphy is clearly visible throughout the glacial period with the most frequent and brightest visible layers appearing during the coldest events. Down to a depth of 2600 m the horizontal layering is very regular; below this depth, small irregularities in the layering start to appear, and below 2800 m the visual stratigraphy becomes more uncertain, perhaps because of penetration into climatically warmer ice. Comparison of the visual stratigraphy with high-resolution continuous records of chemical impurities and dust reveals a high degree of correlation, which indicates that the visible layers are caused by these impurities. A new approach is used to automatically determine annual layer thicknesses from the visual stratigraphy record by carrying out a frequency analysis of the most prominent visible layers in the profile. The result gives strong support for the NorthGRIP timescale model.