  Eruptive mass loss likely produces the energetic outbursts observed from some
massive stars before they undergo core-collapse supernovae (CCSNe). The
resulting dense circumstellar medium (CSM) may also cause the subsequent SNe to
be observed as Type IIn events. The leading hypothesis of the cause of these
outbursts is the response of the envelope of the red supergiant (RSG)
progenitor to energy deposition in the months to years prior to collapse. Early
theoretical studies of this phenomena were limited to 1D, leaving the 3D
convective RSG structure unaddressed. Using FLASH's hydrodynamic capabilities,
we explore the 3D outcomes by constructing convective RSG envelope models and
depositing energies less than the envelope binding energies on timescales
shorter than the envelope dynamical time deep within them. We confirm the 1D
prediction of an outward moving acoustic pulse steepening into a shock,
unbinding the outermost parts of the envelope. However, we find that the
initial 2-4 km/s convective motions seed the intrinsic convective instability
associated with the high entropy material deep in the envelope, enabling gas
from deep within the envelope to escape, increasing the amount of ejected mass
compared to an initially "quiescent" envelope. The 3D models reveal a rich
density structure, with column densities varying by 10x along different lines
of sight. Our work highlights that the 3D convective nature of RSG envelopes
impacts our ability to reliably predict the outburst dynamics, the amount, and
the spatial distribution of the ejected mass associated with deep energy
deposition.
