  Recent observations of gaps and non-axisymmetric features in the dust
distributions of transition disks have been interpreted as evidence of embedded
massive protoplanets. However, comparing the predictions of planet-disk
interaction models to the observed features has shown far from perfect
agreement. This may be due to the strong approximations used for the
predictions. For example, spiral arm fitting typically uses results that are
based on low-mass planets in an isothermal gas. In this work, we describe
two-dimensional, global, hydrodynamical simulations of disks with embedded
protoplanets, with and without the assumption of local isothermality, for a
range of planet-to-star mass ratios 1-10 M_jup for a 1 M_sun star. We use the
Pencil Code in polar coordinates for our models. We find that the inner and
outer spiral wakes of massive protoplanets (M>5 M_jup) produce significant
shock heating that can trigger buoyant instabilities. These drive sustained
turbulence throughout the disk when they occur. The strength of this effect
depends strongly on the mass of the planet and the thermal relaxation
timescale; for a 10 M_jup planet embedded in a thin, purely adiabatic disk, the
spirals, gaps, and vortices typically associated with planet-disk interactions
are disrupted. We find that the effect is only weakly dependent on the initial
radial temperature profile. The spirals that form in disks heated by the
effects we have described may fit the spiral structures observed in transition
disks better than the spirals predicted by linear isothermal theory.
