O01_06

Developing an in-situ ¹⁴C chronology for North Greenland

Søndergaard A¹, Steineman O¹, Haghipour N¹, Wacker L¹, Ivy-Ochs S¹, Larsen N²

¹Laboratory for Ion Beam Physics, Eth Zürich, Zürich, Switzerland, ²Centre for GeoGenetics, GLOBE Institute, Univeristy of Copenhagen, Copenhagen, Denmark

Determining the sensitivity of the Greenland Ice Sheet during the Holocene is a key prerequisite for understanding the future response of the ice sheet to global warming. It has proven difficult to constrain the glacial history of particularly North Greenland using ¹⁰Be exposure dating, an area predicted to be a key component in future mass loss from the ice sheet. This project  will use cosmogenic in-situ ¹⁴C exposure dating to constrain Holocene ice sheet fluctuations in North Greenland.

Cosmogenic nuclides are produced in rocks when cosmic rays hit the surface of the Earth. The cosmogenic nuclide inventory of a rock surfaces is therefore a key tool for chronicling the waxing and waning of ice. The most commonly analyzed nuclide is ¹⁰Be, which has a half-life of 1.4 Myr. However, a particular challenge arises in regions where the ice sheet base is cold and slow-moving. In these regions, erosion rates are low and ¹⁰Be inventories produced during earlier exposure periods accumulate instead of being removed, which result in exposure ages older than the last period of exposure. To circumvent this problem, we use in-situ produced cosmogenic ¹⁴C. Due to the shorter half-life (5730 yr), in-situ ¹⁴C inventories will, contrary ¹⁰Be, decrease not only because of rock surface erosion but also due to shielding from ice cover. Measurements of in-situ ¹⁴C , carried out at the in-situ ¹⁴C  line at Laboratory of Ion Beam Physics, ETH Zürich, can therefore help to obtain more reliable ice reconstructions for North Greenland.