  A notion of the Berry phase is a powerful means to unravel the non-trivial
role of topology in various novel phenomena observed in chiral magnetic
materials and structures. A celebrated example is the intrinsic anomalous Hall
effect (AHE) driven by the non-vanishing Berry phase in the momentum space. As
the AHE is highly dependent on details of the band structure near the Fermi
edge, the Berry phase and AHE can be altered in thin films whose chemical
potential is tunable by dimensionality and disorder. Here, we demonstrate that
in ultrathin SrRuO$_3$ films the Berry phase can be effectively manipulated by
the effects of disorder on the intrinsic Berry phase contribution to the AHE,
which is corroborated by our numerically exact calculations. In addition, our
findings provide ample experimental evidence for the superficial nature of the
topological Hall effect attribution to the protected spin texture and instead
lend strong support to the multi-channel AHE scenario in ultrathin SrRuO$_3$.
