Global Climate Change: Earth and Mars
Initially, let me quote from Colaprete et al's Nature paper v 435 p 184-188 (2005), this is the second to last paragraph discussing the results:
Jakosky and Haberle  suggested that the SPRC may be unstable from year to year, and that small perturbations in climate may result in the SPRC disappearing some years and reappearing in others. In spring, the recession of the seasonal cap is largely controlled by the surface brightness. Although albedos in local regions on the seasonal cap can change rapidly, the persistent asymmetric circulation creates conditions in which relatively larger grain sizes are stable in the Cryptic region through the sublimation season. Any changes to the circulation can result in changes to the surface brightness and poleward heat flow, and thus modify the recession of the cap. The current SPRC albedo is very close to the minimum required for year-round stability . If these albedos are only slightly modified by changes in the location or quantity of precipitation, then the SPRC will undergo significant changes and may partially or completely disappear. The observed changes in polar ice features reported by Malin et al.  and Byrne and Ingersoll [22, 23] are consistent with the notion of a SPRC that is only quasi-stable and may undergo significant changes from one year to the next.
Soon as students stop bugging me ;-) I will finish a write up of what this means, how these models work, and why it matters.