[A-CC29] Ice cores and paleoenvironmental modeling

[ACC29-06] A one-dimensional temperature and age modeling study for evaluation of sites for an oldest ice core around Dome Fuji, Antarctica

★Invited Papers

*Takashi Obase¹, Ayako Abe-Ouchi¹, Fuyuki SAITO², Shun Tsutaki³, Shuji Fujita^3,4, Kenji Kawamura^3,4, Hideaki Motoyama^3,4 (1.Atmosphere and Ocean Research Institute, the University of Tokyo, 2.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3.National Institute of Polar Research, 4.The Graduate University of Advanced Studies (SOKENDAI))

The recovery of a new Antarctic ice core to cover ~1.5 million years (Ma) before present will advance our understanding of the climate system dynamics during Quaternary. Recent glaciological field surveys have been conducted to select the location of the next deep drilling around Dome Fuji (DF), in particular, the spatial distribution of bedrock topography and internal layers of the ice have been acquired by ground-based radar surveys.
In this study, we use a one-dimensional ice flow model to investigate the age of ice, especially in the lowest few hundred meters and thermal conditions at ice-bed interfaces. We investigated the influence from ice thickness, accumulation rate, geothermal heat flux with typical ranges based on glaciological conditions near the DF region. The basal melting rate is diagnosed with a temperature gradient at the ice base. The model results were evaluated with observed age and temperature profiles from DF ice core and borehole temperature observations.
We find that the melting at the ice sheet base is maximum during glacial periods, because the basal temperature lags to the surface temperature. An excessive geothermal heat flux (~5 mW/m2) above the threshold of basal melting can eliminate the old ice, due to the melting during glacial periods. From sensitivity experiments to investigate respective roles of ice thickness and surface mass balance, in the range of typical values of near DF. The one-dimensional model is applied to the vicinity of DF along a 54-km long transect. The results indicate that the model tends to overestimate the age of ice compared to observational isochrones data, suggesting ice thickness is most crucial factor for consideration and evaluation of sites for drilling.