Munk worked on a wide range of topics, including surface waves, geophysical implications of variations in the Earth's rotation, tides, internal waves, deep-ocean drilling into the sea floor, acoustical measurements of ocean properties, sea level rise, and climate change. Beginning in 1975, Munk and Carl Wunsch developed ocean acoustic tomography, to exploit the ease with which sound travels in the ocean and use acoustical signals for measurement of broad-scale temperature and current. In a 1991 experiment, Munk and his collaborators investigated the ability of underwater sound to propagate from the Southern Indian Ocean across all ocean basins. The aim was to measure global ocean temperature. The experiment was criticized by environmental groups, who expected that the loud acoustic signals would adversely affect marine life. Munk continued to develop and advocate for acoustical measurements of the ocean throughout his career.