  High-resolution broadband filtergrams of active region NOAA 11271 in Ca ii H
and G band were obtained with the Solar Optical Telescope on board Hinode to
identify the physical driver responsible for the dynamic and small-scale
chromospheric jets above a sunspot light bridge. We identified the jets in the
Ca images using a semi-automatic routine. The chromospheric jets consist of a
bright, triangular-shaped blob that lies on the light bridge, while the apex of
this blob extends into a spike-like structure that is bright against the dark
umbral background. Most of the jets have apparent lengths of less than 1000 km
and about 30% of them have lengths between 1000-1600 km. They are oriented
within +/-35 deg. to the normal of the light bridge axis. Many of them are
clustered near the central part within a 2 arcsec area. The jets are seen to
move rapidly along the light bridge and most of them cannot be identified in
successive images taken with a 2 min cadence. The jets are primarily located on
one side of the light bridge and are directed into the umbral core. The Stokes
profiles at or close to the location of the blobs on the LB exhibit both a
significant net circular polarization and multiple components, including
opposite-polarity lobes. The magnetic field diverges from the light bridge
towards the umbral cores that it separates. In the photosphere there is a
predominantly uni-directional flow with speeds of 100-150 m/s along the light
bridge which is interrupted by a patch of weak motions that also moves along
the light bridge. The dynamic short-lived jets above the LB seem to be guided
by the magnetic field lines. Reconnection events are a likely trigger for such
phenomenon since they occur at locations where the magnetic field changes
orientation sharply. We find no clear relation between the jets and the
photospheric flow pattern.
