Enhanced buoyancy of active particles in convective flows

We numerically investigated the diffusion of a heavy active Brownian particle in a linear periodic array of steady planar counter-rotating convection rolls at high Peclet numbers. We show that, under certain conditions, the particle rises to the surface even if it is denser than the suspension fluid, and floats there for exceedingly long times. Such an apparently counterintuitive phenomenon of ``enhanced buoyancy{''} is a combined effect of gravity, advection, and shear torque.