Using Radar Layer Data in Ice-Sheet Models.

Abstract:

Deep radar layers emanate from surface deposition of electrolytes, and the subsequent motion and deformation of firn and ice determines the geometry of these passive tracers. They contain information about the integrated history of the ice-dynamics since their deposition, and can be used to infer accumulation rate, melt-rate, ice rheology and ice-thickness history. This paper will examine how this principle meets with practice, with the aim of seeing how well we can answer the following questions.

How should data best be presented to modellers? The geometrical information in radar layers is completely encoded in their slope at any point, and these slopes are the raw data from which line picks are made. The implication is that models should be matched against slope data, rather than reconstituted picks, as the picking method has the potential to introduce systematic errors that are difficult to account for in any inversion process. The choice of data style presented to model has implications for the following questions.

How accurately can we reconstitute accumulation rate and thickness variations in space and in time? What are the prospects for inverting for ice rheological parameters? Which other techniques can be usefully used with isochrone layes to improve these estimates? The answers to these questions depend both on the dynamics and mechanics of the problem, and also on the data errors in the radar layers.