Nontwist systems, common in the dynamical descriptions of fluids and plasmas, possess a shearless curve with a concomitant transport barrier that eliminates or reduces chaotic transport, even after its breakdown. In order to investigate the transport properties of nontwist systems, we analyze the barrier escape time and barrier transmissivity for the standard nontwist map, a paradigm of such systems. We interpret the sensitive dependence of these quantities upon map parameters by investigating chaotic orbit stickiness and the associated role played by the dominant crossing of stable and unstable manifolds. © 2009 American Institute of Physics. ͓doi:10.1063/1.3247349͔Nonmonotonic flows with reverse shear are observed in many physical systems. Much previous research indicates that transport properties of such systems can be well described by area preserving maps. Many examples exist, e.g., in the fields of fluid mechanics and plasma physics; in particular, in models that describe zonal flows that occur in geophysics, atmospheric science, and fusion plasma physics. The standard nontwist map (SNM) is a well-known paradigm for investigating transport in reverse shear systems. The nonmonotonicity property of the SNM gives rise to transport barriers due to robust tori (invariant curves) that occur in zonal flows. These tori separate regions of the two-dimensional phase space. Moreover, the influence of these barriers on the transport remains even after the breakup of the tori. This phenomenon, i.e., the difficulty encountered in crossing broken barriers, is explained by examining the stickiness of orbits that occur in some regions of the map phase space. For a certain range of control parameters, these regions emerge near resonances. The presence of stickiness is closely related to the structure of the stable and unstable manifolds of hyperbolic orbits, becoming prevalent when the manifolds reconnect and change from a dominant homoclinic tangle to a combination that includes both homoclinic and heteroclinic tangles.