How can methylmercury in the ocean be reabsorbed into the atmosphere?
Much of the methyl mercury that enters the atmosphere may be dimethyl mercury, $\text{(CH}_3\text{)}_2\text{Hg}$.  This is a very volatile compound which, if it were pure, would have 50 mm mercury or more vapor pressure at 20°C.  Complexes involving more electronegative ligands, such as the chloride $\text{CH}_3\text{HgCl}$, are significantly less volatile, but still have more vapor pressure than purely inorganic mercury compounds.