  Linear polarization maps of the Carina Nebula were obtained at 250, 350, and
500 $\mu$m during the 2012 flight of the BLASTPol balloon-borne telescope.
These measurements are combined with Planck 850 $\mu$m data in order to produce
a submillimeter spectrum of the polarization fraction of the dust emission,
averaged over the cloud. This spectrum is flat to within $\pm$15% (relative to
the 350 $\mu$m polarization fraction). In particular, there is no evidence for
a pronounced minimum of the spectrum near 350 $\mu$m, as suggested by previous
ground-based measurements of other molecular clouds. This result of a flat
polarization spectrum in Carina is consistent with recently-published BLASTPol
measurements of the Vela C molecular cloud, and also agrees with a published
model for an externally-illuminated, dense molecular cloud by Bethell and
collaborators. The shape of the spectrum in Carina does not show any dependence
on the radiative environment of the dust, as quantified by the Planck-derived
dust temperature or dust optical depth at 353 GHz.
