Temporal evolution of a sunspot in a 6.144 Mm deep domain. The bottom boundary is symmetric in all three mass flux components. The sunspot is decaying on a timescale of about 3–6 hr due to interchange instabilities developing near the bottom of the domain. The field-free plasma intruding near the bottom boundary leads to buoyant upflows that develop islands of granulation within the umbra of the spot. After about 6 hr most of the magnetic field is dispersed into a structure the size of a few pores.