Dr. Johns is a seagoing oceanographer specializing in the use of long-term moored instrumentation to study ocean circulation. His research involves studies of the large-scale wind-driven circulation, with emphasis on the dynamics of western boundary currents, and on deep flows related to the global thermohaline circulation and climate variability. Dr. Johns also studies the dynamics of straits and the exchange processes between the oceans and marginal seas, including marginal sea overflows.