  We present new HST/WFC3-IR narrowband [Fe II] images of protostellar jets in
the Carina Nebula. Combined with 5 previously published sources, we have a
sample of 18 jets and 2 HH objects. All of the jets we targeted with WFC3 show
bright infrared [Fe II] emission, and a few H$\alpha$ candidate jets are
confirmed as collimated outflows based on the morphology of their [Fe II]
emission. Continuum-subtracted images clearly separate jet emission from the
adjacent ionization front, providing a better tracer of the collimated jet than
H$\alpha$ and allowing us to connect these jets with their embedded driving
sources. The [Fe II] 1.64 $\mu$m/H$\alpha$ flux ratio measured in the jets is
$\gtrsim 5$ times larger than in the adjacent ionization fronts. The
low-ionization jet core requires high densities to shield Fe$^+$ against
further ionization by the FUV radiation from O-type stars in the H II region.
High jet densities imply high mass-loss rates, consistent with the
intermediate-mass driving sources we identify for 13 jets. The remaining jets
emerge from opaque globules that obscure emission from the protostar. In many
respects, the HH jets in Carina look like a scaled-up version of the jets
driven by low-mass protostars. Altogether, these observations suggest that [Fe
II] emission is a reliable tracer of dense, irradiated jets driven by
intermediate-mass protostars. We argue that highly collimated outflows are
common to more massive protostars, and that they suggest the outflow physics
inferred for low-mass stars formation scales up to at least $\sim8$
M$_{\odot}$.
