Sample, Log, Repeat: the quest for dating the retreat of the British Irish Ice Sheet

Posted by lcb14 at Aug 24, 2015 10:22 AM |
On 3 July 2015 Sally Morgan from the Geophysics, Rock Physics and Borehole Research Group departed on a month-long research cruise (JC123) as part of the BRITICE-CHRONO project.

The JC123 cruise, led by Professor Colm O’Cofaigh of Durham University, is the second of 2 marine-based coring programmes that are central to the 5-year BRITICE-CHRONO NERC Consortium Grant which aims to collect and date material to constrain the timing and rates of change of the collapsing British-Irish Ice Sheet (BIIS). This is key to predicting the future rates of change of large ice masses, such as West Antarctic and Greenland ice Sheets, currently severely limited by a lack of data to underpin numerical models. Scientists from a number of institutions staffed this year’s project, including researchers based at the universities of Bangor, Durham, Leicester, Liverpool, Sheffield, Stirling, and Ulster, as well as the British Geological Survey.

The first BRITICE-CHRONO cruise (JC106) took place in 2014, and the 2015 JC123 was once again on board the Royal Research Ship James Cook and set sail from Southampton. The cruise surveyed and sampled material along 3 main transects in The Minch, Shetland and the North Sea areas. Coring targets in these transects were identified using primarily multibeam echo sounder and sub-bottom profiler data collected during this cruise. Most cores were acquired utilising the British Geological Survey’s vibrocorer system (up to 6 m penetration), with a few cores sampled using the National Oceanographic Centre’s piston corer (up to 10 m penetration). Over 170 individual cores were collected, totalling in excess of half a kilometre of core material.

Once recovered to the ship, the cores were cut into metre-long sections, curated, then measured on Leicester’s containerised Geotek multi-sensor core logger system, operated by Sally. This system allows for the acquisition of the physical properties of the cores, including the bulk density, acoustic velocity, magnetic susceptibility and electrical resistivity. Once measured, cores were returned to the description team who split them in half lengthways, sampled and described the cores, and then packed them up ready for shipment to different institutions at the end of the cruise for further analyses (including C14-dating and optically stimulated luminescence dating) and archiving. Used in combination with the descriptions and geochronological data derived from the cores, the physical properties data will be used to help better understand the timing of the BIIS retreat at the end of the last glaciation.

Work on the cores acquired during the 2014 (JC123) and 2015 (JC106) cruises, and material collected from the equivalent land-based studies, will continue through 2017, aiming to significantly improve predictive ice sheet modelling, with the BIIS forming an important benchmark.

Further information about the project is available via the BRITICE-CHRONO and you can also follow the project’s progress on Twitter: @BRITICECHRONO

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