  Temporal variability in the photometric and spectroscopic properties of
protoplanetary disks is common in YSO. However, evidence pointing toward
changes in their morphology over short timescales has only been found for a few
sources, mainly due to a lack of high cadence observations at mas resolution.
We combine GRAVITY multi-epoch observations of HD98922 at mas resolution with
PIONIER archival data covering a total time span of 11 years. We interpret the
interferometric visibilities and spectral energy distribution with geometrical
models and through radiative transfer techniques. We investigated
high-spectral-resolution quantities to obtain information on the properties of
the HI BrG-line-emitting region. The observations are best fitted by a model of
a crescent-like asymmetric dust feature located at 1 au and accounting for 70%
of the NIR emission. The feature has an almost constant magnitude and orbits
the central star with a possible sub-Keplerian period of 12 months, although a
9 month period is another, albeit less probable, solution. The radiative
transfer models show that the emission originates from a small amount of
carbon-rich (25%) silicates, or quantum-heated particles located in a
low-density region. Among different possible scenarios, we favor hydrodynamical
instabilities in the inner disk that can create a large vortex. The high
spectral resolution differential phases in the BrG-line show that the hot-gas
component is offset from the star and in some cases is located between the star
and the crescent feature. The scale of the emission does not favor
magnetospheric accretion as a driving mechanism. The scenario of an asymmetric
disk wind or a massive accreting substellar or planetary companion is
discussed. With this unique observational data set for HD98922, we reveal
morphological variability in the innermost 2 au of its disk region.
