  Observations of proxies of the magnetic helicity in the Sun over the past two
solar cycles revealed reversals of the helicity hemispheric sign rule (negative
in the North and positive in the South hemispheres). We apply the mean-field
solar dynamo model to study the reversals of the magnetic helicity sign for the
dynamo operating in the bulk of the solar convection zone. The evolution of the
magnetic helicity is governed by the conservation law. We found that the
reversal of the sign of the small-scale magnetic helicity follows the dynamo
wave propagating inside the convection zone. Therefore, the spatial patterns of
the magnetic helicity reversals reflect the processes which contribute to
generation and evolution of the large-scale magnetic fields. At the surface the
patterns of the helicity sign reversals are determined by the magnetic helicity
boundary conditions at the top of the convection zone. We demonstrate the
impact of fluctuations in the dynamo parameters and variability in dynamo cycle
amplitude on the reversals of the magnetic helicity sign rule. The obtained
results suggest that the magnetic helicity of the large-scale axisymmetric
field can be treated as an additional observational tracer for the solar
dynamo.
