Mass balance for a meteoric ice layer of the Amery Ice Shelf, East Antarctica

Snow accumulation on the upper surface and melting from the lower surface are important to the mass balance of an ice shelf. However the ice shelf surface accumulation measurements are only available from stakes, firn-core records and automatic weather station (AWS) measurements. The total mass balance can be obtained from the continuity equation by employing the steady-state assumption. But it is hardly used to calculate the mass balance, due to the lack of spatially continuous data, the uncertainty of ice flow properties, and other limitations. With the recently structural glaciological description and more updated datasets, a modified mass-balance model for a meteoric ice layer was developed and applied to a longitudinal flowband of the Amery ice shelf, East Antarctica. The datasets of ice velocity and meteoric ice thickness are employed. Here, the changes in ice flow velocity, meteoric ice thickness on the centre flowline, as well as flowband width with the distance along the flowband was modeled by piecewise cubic polynomial fitting. The original model overestimates the mass balance. We introduce a ratio to modify it model with only one observation. The model was then used to simulate the mass balance of a meteoric ice layer along a longitudinal flowband that extends some 300 km all way to the calving front. Sensitivity tests showed that the modeled mass balance is nearly equally sensitive to changes in ice flow velocity, ice thickness, and flow width. But there is more uncertainty with changes in flow width because the flowband boundary is delineated manually. The results were compared to observations and previous studies, which showed that the model ignoring the changes in flow width has better simulation result. The calculated specific mass balance of the meteoric ice layer is from 0.6812 m/a near the ice shelf front to -0.2645 m/a 300 km far away from the ice shelf front.