  Breathing oscillations of skyrmions in chiral antiferromagnets can be excited
by a temporal modification of the Dzyaloshinskii-Moriya interaction or
magnetocrystalline anisotropy strength. We employ an adiabatic approximation
and derive a formula for the potential that directly implies breathing
oscillations. We study the nonlinear regime and the features of larger
amplitude oscillations. We show that there is a maximum amplitude supported by
the potential. As a consequence, we predict theoretically and observe
numerically skyrmion annihilation events due to excitation of large amplitude
breathing oscillations. The process is efficient when the skyrmion is mildly
excited so that its radius initially grows, while the annihilation event is
eventually induced by the internal breathing dynamics. We reveal the
counter-intuitive property that the skyrmion possesses a nonzero kinetic energy
at the moment of its annihilation. Finally, the frequency of small amplitude
breathing oscillations is determined.
