  Horizon-scale observations from the Event Horizon Telescope (EHT) have
enabled precision study of supermassive black hole accretion. Contemporary
accretion modeling often treats the inflowing plasma as a single, thermal
fluid, but microphysical kinetic effects can lead to significant deviations
from this idealized picture. We investigate how the helicity barrier influences
EHT-accessible electromagnetic observables by employing a simple model for
electron heating based on kinetic physics and the cascade of energy and
helicity in unbalanced turbulence. Although the helicity barrier plays only a
minor role in regions with high plasma-beta, like in SANE disks, it may
substantially impact in regions with more ordered magnetic fields, such as the
jet and its surrounding wind in SANE flows as well as throughout the entire
domain in MAD flows. In SANE flows, emission shifts from the funnel wall
towards the lower-magnetization disk region; in MAD flows the emission
morphology remains largely unchanged. Including the helicity barrier leads to
characteristically lower electron temperatures, and neglecting it can lead to
underestimated accretion rates and inferred jet powers. The corresponding
higher plasma densities result in increased depolarization and Faraday depths
thereby decreasing the amplitude of the beta_2 coefficient while leaving its
angle unchanged. Both the increased jet power and lower |beta_2| may help
alleviate outstanding tensions between modeling and EHT observations. We also
find that the estimated ring diameter may be underestimated when the helicity
barrier is neglected. Our results underscore the significance of the helicity
barrier in shaping black hole observables and inferred accretion system
parameters.
