  We conduct athermal simulations of freely-cooling, viscous soft spheres
around the jamming transition density \phi_{J}, and find evidence for a growing
length \xi(t) that governs relaxation to mechanical equilibrium. \xi(t) is
manifest in both the velocity correlation function, and the spatial
correlations in a scalar measure of local force balance which we define. Data
for different densities \phi can be collapsed onto two master curves by scaling
\xi(t) and t by powers of |\phi-\phi_{J}|, indicative of critical scaling.
Furthermore, particle transport for \phi>\phi_{J} exhibits aging and
superdiffusion similar to a range of soft matter experiments, suggesting a
common origin. Finally, we explain how \xi(t) at late times maps onto known
behavior away from \phi_{J}.
