Talk by Bryn Hubbard, Aberystwyth University – Niels Bohr Institute - University of Copenhagen

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Talk by Bryn Hubbard, Aberystwyth University

Ice borehole optical televiewing and its application to the NEEM deep borehole, Greenland

This talk will introduce the technique of optical televiewing (OPTV) of ice boreholes, including initial application to valley glaciers to determine multiple structural generations. Subsequent application of OPTV to accumulating surfaces on ice sheets and ice shelves will be summarized, including the principles of layer counting, density reconstruction and melt layer reconstruction from OPTV images. A case study of two contrasting sites on the Roi Baudouin Ice Shelf, Antarctica, will be presented. The talk will then focus on OPTV records from the NEEM shallow and deep boreholes, Greenland, presenting density reconstruction and layer counting from the shallow firn borehole before moving on to the deep borehole, the complete (~2.5 km) length of which was logged by OPTV in 2012. Logistical aspects of the OPTV logging will be presented, along with features of interest from the resulting borehole log. These will include: the log’s overall luminosity profile, suggesting the presence of several ice facies; the identification of regularly-repeated and irregular layers along the log; the geometrical reconstruction of dipping, debris-rich basal ice layers, and the presence of occasional inclusions in the OPTV log.