Interpretation of the Temperature Profile Measured at Vostok, East Antarctica

The temperature profile measured in the Vostok bore hole is analysed. The temperature distribution in polar ice sheets depends mainly on past surface temperature, geothermal flux, and accumulation rate. In the present work, the heat equation is solved both for ice and for the underlying bedrock. The Vostok ice core offers a 160 000 year climatic record which is used to define the past surface temperature, while accumulation-rate variations are assumed to be governed by the saturation vapour pressure. The model is run for a number of different sets of parameters in order to find the parameter associations giving a good fit between the observed and the computed temperature profiles. With this model, it is possible to simulate the measured temperature profile within 0.1°C. To obtain this good fit, geothermal flux has to be higher than 50 mW/m2 and present-day accumulation rate must be lower than 2.6 cm/year. Sensitivity of these results both to the amplitude of surface-temperature change and to the velocity profile with depth is also investigated. Finally, it is shown that ice is at the melting point at the base of the ice sheet, which is in agreement with the presence of a subglacial lake near Vostok Station.