Abstract
Cosmogenic nuclides are widely used to constrain the landscape history of glaciated areas. At nunataks in continental polar regions with extremely arid conditions, cosmogenic nuclides are often the only method available to date the ice thinning history of the glacier. However, the amount of cosmogenic isotopes accumulated at the surface of nunataks depends not only on the length of time that rock has been exposed since the last deglaciation but also on the full history of the surface, including muon production under ice, exposure during previous interglacials, subaerial weathering rate, glacial erosion rate, and uplift rate of the nunatak. The NUNAtak Ice Thinning model (NUNAIT) simulates the cosmonuclide accumulation on vertical profiles, fitting the aforementioned parameters to a set of multi-isotope apparent ages from samples taken at different elevations over the ice-sheet surface. The NUNAIT calculator is an easy-to-use tool that constrains parameters that describe the geological history of a nunatak from a set of surface exposure ages.
Highlights
Cosmogenic signatures at the surface of nunataks are the result of the intermittent exposure of the surfaces to cosmic radiation through the glacial cycles (e.g., [4]), glacial erosion (e.g., [5,6]), and the subaerial weathering of these surfaces (e.g., [7])
The NUNAtak Ice Thinning model (NUNAIT) and previous models described by Stroeven et al [4], Li et al [9], and Knudsen et al [10] are based on the same principle: using a climate proxy (δ18O record) to solve complex exposure-burial histories that fit the surface cosmogenic nuclide data
Previous models focused on solving the problem for sets of multiple isotope data from single samples
Summary
Quantifying the changes in the thickness of the Greenland and Antarctic ice sheets is key to understanding future sea-level rise [1]. The model they used is based on complex exposure-burial histories forced along the ice-free/ice-covered conditions provided by a marine oxygen isotope δ18O proxy glacial record In this model, a given δ18O cutoff value defines when the surface of the tor is exposed or shielded from cosmic radiation. Knudsen et al [10] described a method to solve the δ18O cutoff value and the glacial and interglacial erosion rates from a set of multiple cosmonuclide concentrations that can include 10Be, 26Al, 14C, and/or 21Ne data. The NUNAtak Ice Thinning (NUNAIT) calculator presented here solves (1) the elevation history of the ice surface, (2) the glacial erosion rate, (3) the subaerial weathering rate, and (4) the nunatak uplift rate from a multi-sample (elevation profile) and multi-isotope (10Be, 26Al, 21Ne, 3He, 36Cl, and/or 14C) data set. This type of file is generated at the end of each fitting session with the same name as the input file and _model.mat
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