  We present measurements of proper motions and radial velocities of four
powerful Herbig-Haro (HH) jets in the Carina nebula: HH 666, HH 901, HH 902,
and HH 1066. Two epochs of Hubble Space Telescope (HST) imaging separated by a
time baseline of ~4.4 years provide proper motions that allow us to measure the
transverse velocities of the jets, while ground-based spectra sample their
Doppler velocities. Together these yield full three-dimensional space
velocities. Aside from HH 666, their identification as outflows was previously
inferred only from morphology in images. Proper motions now show decisively
that these objects are indeed jets, and confirm that the intermediate-mass
protostars identified as the candidate driving sources for HH 666 and HH 1066
are indeed the origin of these outflows. The appearance of two new knots in the
HH 1066 jet suggest recent (~35 yr) changes in the accretion rate, underscoring
the variable nature of accretion and outflow in the formation of
intermediate-mass stars. In fact, kinematics and mass-ejection histories for
all the jets suggest highly episodic mass loss, and point toward pronounced
accretion fluctuations. Overall, we measure velocities similar to those found
for low-mass protostars. However, the HH jets in Carina have higher densities
and are more massive than their low-mass counterparts. Coarse estimates suggest
that the heavy jets of intermediate-mass protostars can compete with or even
exceed inject ~10 or more times the cumulative momentum injection of lower-mass
protostars.
