| Summary: | Numerous field and laboratory observations indicate how multiple factors influence the dynamicsof polar ice masses. These include the large-scale flow pattern, stress- magnitude, temperatureand ice microstructure. Data obtained from polar ice cores, and their corresponding boreholes,provides a valuable resource for evaluating the flow relations for ice used in ice sheet models. Inthis study we use ice microstructure, temperature and strain rate observations from the DomeSummit South (DSS) ice-coring site at Law Dome to compare four anisotropic flow relations forpolycrystalline ice. Observations from laboratory ice deformation experiments are used to guideassessment of the flow relation predictions for the DSS site. The flow relations in which therheology is parameterised by a scalar anisotropic function, so that the strain rate and deviatoricstress tensor components are collinear, provide the most realistic simple shear and verticalcompression stress profiles for the DSS site. Those flow relations where i) the anisotropy isderived from the magnitude of applied stresses resolved onto the basal planes of individual grainsand ii) the macroscopic deformation is obtained via homogenisation of individual grain responses,provide stress estimates inconsistent with observations from experiments conducted in combinedsimple shear and vertical compression stress configurations that are similar to conditions at theDSS site. This analysis highlights the difficulties associated with the development of flow relationswhich incorporate a physically-based description of microdeformation processes. In particular,this approach requires the adequate parameterisation of all relevant microdeformation,recrystallisation and recovery processes.
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