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In situ cosmogenic radiocarbon production and 2-D ice flow line modeling for an Antarctic blue ice area

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  • Radiocarbon measurements at ice margin sites and blue ice areas can potentially be used for ice dating, ablation rate estimates and paleoclimatic reconstructions. Part of the measured signal comes from in situ cosmogenic ¹⁴C production in ice, and this component must be well understood before useful information can be extracted from ¹⁴C data. We combine cosmic ray scaling and production estimates with a two-dimensional ice flow line model to study cosmogenic ¹⁴C production at Taylor Glacier, Antarctica. We find (1) that ¹⁴C production through thermal neutron capture by nitrogen in air bubbles is negligible; (2) that including ice flow patterns caused by basal topography can lead to a surface ¹⁴C activity that differs by up to 25% from the activity calculated using an ablation-only approximation, which is used in all prior work; and (3) that at high ablation margin sites, solar modulation of the cosmic ray flux may change the strength of the dominant spallogenic production by up to 10%. As part of this effort we model two-dimensional ice flow along the central flow line of Taylor Glacier. We present two methods for parameterizing vertical strain rates, and assess which method is more reliable for Taylor Glacier. Finally, we present a sensitivity study from which we conclude that uncertainties in published cosmogenic production rates are the largest source of potential error. The results presented here can inform ongoing and future ¹⁴C and ice flow studies at ice margin sites, including important paleoclimatic applications such as the reconstruction of paleoatmospheric ¹⁴C content of methane.
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  • Buizert, C., V. V. Petrenko, J. L. Kavanaugh, K. M. Cuffey, N. A. Lifton, E. J. Brook, and J. P. Severinghaus (2012), In situ cosmogenic radiocarbon production and 2-D ice flow line modeling for an Antarctic blue ice area, J. Geophys. Res., 117, F02029, doi:10.1029/2011JF002086.
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  • 117
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  • F02029
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  • V. V. Petrenko has been supported by the NOAA Postdoctoral Fellowship in Climate and Global Change, NSF grants 0632222 and 0806387 (White) and NSF grant 0839031 (Severinghaus); this work was partially supported by NSF grant OPP-0125579 to K. M. Cuffey and NSF grant 0838936 to E. J. Brook; N. A. Lifton is grateful for support by the CRONUS-Earth project (NSF EAR0345150) and the University of Arizona Accelerator Mass Spectrometry Laboratory.
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