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The Cryosphere, 12, 1651-1663, 2018
https://doi.org/10.5194/tc-12-1651-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
15 May 2018
Where is the 1-million-year-old ice at Dome A?
Liyun Zhao1,3, John C. Moore1,3,4, Bo Sun2, Xueyuan Tang2, and Xiaoran Guo1 1College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China
2Polar Research Institute of China, Shanghai 200129, China
3Joint Center for Global Change Studies (JCGCS), Beijing 100875, China
4Arctic Centre, University of Lapland, P.O. Box 122, 96101 Rovaniemi, Finland
Abstract. Ice fabric influences the rheology of ice, and hence the age–depth profile at ice core drilling sites. To investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric measurements around Dome A along with prescribed fabrics ranging from isotropic through girdle to single maximum in a three-dimensional, thermo-mechanically coupled full-Stokes model of a 70  ×  70 km2 domain around Kunlun station. This model allows for the simulation of the near basal ice temperature and age, and ice flow around the location of the Chinese deep ice coring site. Ice fabrics and geothermal heat flux strongly affect the vertical advection and basal temperature which consequently control the age profile. Constraining modeled age–depth profiles with dated radar isochrones to 2∕3 ice depth, the surface vertical velocity, and also the spatial variability of a radar isochrones dated to 153.3 ka BP, limits the age of the deep ice at Kunlun to between 649 and 831 ka, a much smaller range than previously inferred. The simple interpretation of the polarimetric radar fabric data that we use produces best fits with a geothermal heat flux of 55 mW m−2. A heat flux of 50 mW m−2 is too low to fit the deeper radar layers, and 60 mW m−2 leads to unrealistic surface velocities. The modeled basal temperature at Kunlun reaches the pressure melting point with a basal melting rate of 2.2–2.7 mm a−1. Using the spatial distribution of basal temperatures and the best fit fabric suggests that within 400 m of Kunlun station, 1-million-year-old ice may be found 200 m above the bed, and that there are large regions where even older ice is well above the bedrock within 5–6 km of the Kunlun station.
Citation: Zhao, L., Moore, J. C., Sun, B., Tang, X., and Guo, X.: Where is the 1-million-year-old ice at Dome A?, The Cryosphere, 12, 1651-1663, https://doi.org/10.5194/tc-12-1651-2018, 2018.
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Short summary
We investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, using the depth-varying anisotropic fabric suggested by the recent polarimetric measurements in a three-dimensional, thermo-mechanically coupled full-Stokes model. The model results suggest that the age of the deep ice at Kunlun is 649–831 ka, and there are large regions where 1-million-year-old ice may be found 200 m above the bedrock within 5–6 km of the Kunlun station.
We investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun...
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