We present an Arrhenius analysis of self-diffusion on the prismatic surface of ice calculated from 
molecular dynamics simulations. The six-site water model of Nada and van der Eerden was used in 
combination with a structure-based criterion for determining the number of liquid-like molecules 
in the quasi-liquid layer. Simulated temperatures range from 230 K . 287 K, the latter being just 
below the melting temperature of the model, 289 K. Calculated surface diffusion coefficients agree 
with available experimental data to within quoted precision. Our results indicate positive Arrhenius 
curvature, implying a change in the mechanism of self-diffusion from low to high temperature, with 
a concomitant increase in energy of activation from 29.1 kJ/mol at low temperature to 53.8 kJ/mol 
close to the melting point. In addition, we find that the surface self-diffusion is anisotropic at 
lower temperatures, transitioning to isotropic in the temperature range of 240-250 K.  We also 
present a framework for self-diffusion in the quasi-liquid layer on ice that aims to explain 
these observations.