Karst landscapes provide unique challenges and opportunities to studies of processes within the critical zone, which spans from the top of the canopy to the base of active groundwater circulation. Dimensional analysis using the characteristic length scales and time scales of karst processes enables development of an initial framework for quantification of the rates and distribution of these processes throughout the critical zone. In particular, dimensional analysis provides a useful tool with which to identify the relative importance of different processes and to test the assumptions behind models of critical zone function. I briefly review prior use of dimensional analysis to understand various aspects of the karst critical zone and then introduce simple models for CO₂ transport within fractures and conduits of the vadose zone. Dimensional analysis of these models suggests that advection through karst fractures within both the gas and liquid phases will strongly impact vertical CO₂ profiles in the vadose zone in a variety of settings. Implications of this finding for karst critical zone development and future data campaigns are discussed.