  Tidally locked worlds provide a unique opportunity for constraining the
probable climates of certain exoplanets. They are unique in that few exoplanet
spin and obliquity states are known or will be determined in the near future:
both of which are critical in modeling climate. A recent study shows the
dynamical conditions present in the TRAPPIST-1 system make rotation and large
librations of the substellar point possible for these planets, which are
usually assumed to be tidally locked. We independently confirm the tendency for
planets in TRAPPIST-1-like systems to sporadically transition from tidally
locked libration to slow rotation using N-body simulations. We examine the
nature and frequency of these spin states to best inform energy balance models
which predict the temperature profile of the planet's surface. Our findings
show that tidally locked planets with sporadic rotation are able to be in both
long-term persistent states and states with prolonged transient behavior: where
frequent transitions between behaviors occur. Quasi-stable spin regimes, where
the planet exhibits one spin behavior for up to hundreds of millennia, are
likely able to form stable climate systems while the spin behavior is constant.
1D energy balance models show that tidally locked planets with sporadic
rotation around M-dwarfs will experience a relatively small change in
substellar temperature due to the lower albedo of ice in an infrared dominant
stellar spectrum. The exact effects of large changes in temperature profiles on
these planets as they rotate require more robust climate models, like 3D global
circulation models, to better examine.
