"Cloud seeding" geoengineering -- i.e. deliberately increasing the albedo of low-level marine clouds by injecting them with sea salt aerosols -- is simulated in a coupled mixed layer ocean-atmosphere general circulation model. Seeding stratocumulus decks over three subtropical maritime regions produces strong local radiative deficits, both due to enhancement of the local cloud albedo and direct scattering of solar radiation by the added sea salts. Resulting cooling is fairly well spread over most of the globe. However, differential cooling over the equatorial Pacific Ocean induces enhanced La Niņa conditions, which is evidenced in the precipitation response. Additionally, model runs in which only one of the three regions is seeded indicate some nonlinearity in the temperature response. We identify dynamical and thermodynamical constraints on the temperature and hydrological cycle response, respectively, that will aid in constraining how the climate would respond to cloud seeding.