Modelling accreted ice in subglacial Lake Vostok, Antarctica

The distribution and thickness of accreted ice at the ice-lake interface of subglacial Lake Vostok, East Antarctica, is calculated conflating various sources: ( 1) The modelled basal mass balance at the ice-lake interface based on two different bathymetry models, ( 2) different ice flow trajectories obtained from satellite interferometry and ice penetrating radar measurements, and ( 3) reasonable ice flow velocity. Our results show that the accreted ice distribution is highly sensitive to the ice draft and to the used flow line directions. The volume and thickness of the accreted ice depends significantly on the ice flow velocity. According to our modelling, we estimate the accreted ice area, volume and mean thickness to be 10,800 +/- 500 km(2), 980 +/- 200 km(3), and 90 +/- 45 m, respectively, for an ice flow velocity of 3.6 m/a. Only about 36 +/- 2% of Lake Vostok's surface is in contact with meteoric ice, melted by about 2.65 +/- 0.10 cm/a. This has impacts on the sedimentation rate and the supply of nutrients, oxygen, and/or other components only present in meteoric ice but not in accreted lake ice. We estimate the residence time of the lake water at about 32,000 +/- 4000 years.