  Experimental measurements of plasma and neutral profiles across the pedestal
are used in conjunction with 2D edge modeling to examine pedestal stiffness in
Alcator C-Mod H-mode plasmas. Experiments on Alcator C-Mod observed pedestal
degradation and loss in confinement below a critical value of net power
crossing the separatrix, $P_\mathrm{net} = P_\mathrm{net}^\mathrm{crit} \approx
2.3$ MW. New analysis of ionization and particle flux profiles reveal
saturation of the pedestal electron density, $n_{e}^\mathrm{ped}$ despite
continuous increases in ionization throughout the pedestal, inversely related
to $P_\mathrm{net}$. A limit to the pedestal $\nabla n_{e}$ emerges as the
particle flux, $\Gamma_{D}$ continues to grow, implying increases in the
effective particle diffusivity, $D_\mathrm{eff}$. This is well-correlated with
the separatrix collisionality, $\nu^{*}_\mathrm{sep}$ and a turbulence control
parameter, $\alpha_{t}$, implying a possible transition in type of turbulence.
The transition is well correlated with the experimentally observed value of
$P_\mathrm{net}^\mathrm{crit}$. SOLPS-ITER modeling is performed for select
discharges from the power scan, constrained with experimental electron and
neutral densities, measured at the outer midplane. The modeling confirms
general growth in $D_\mathrm{eff}$, consistent with experimental findings, and
additionally suggests even larger growth in $\chi_{e}$ at the same
$P_\mathrm{net}^\mathrm{crit}$.
