The Ocean Sciences Section of AGU was one of the union's original sections. It was founded in 1920 as the physical oceanography section and renamed the Ocean Sciences Section in 1923. The list of past presidents contains some of the leading names of the field. The section currently (April 2015) has over 6000 members, with primary affiliations as follows:
- Biological Oceanography 1121
- Marine Geochemistry 1591
- Marine Geology and Geophysics 2296
- Physical Oceanography 2730
- Ocean Sciences 3467
Charged with exploring three fourths of the planet, the Ocean Sciences Section is necessarily large and inclusive. The section welcomes members whose primary interests are marine related, regardless of discipline. It recently re-organized into four subsections that provide a clearer focus for participation in AGU activities: biological oceanography, marine geochemistry, marine geology and geophysics, and physical oceanography. Across these disciplines, members are academic and research scientists, engineers, policy-makers, and administrators. Members study processes in environments ranging from the coast through the open ocean, and they develop and use a wide range of highly technical instrumentation ranging from remote sensors to autonomous devices to ship-related sampling gear. The oceans are important for our quality of life, its fisheries and mineral resources, for transport, and its role in the climate system. Some of the exciting research emerging is related to the role of the oceans in the climate system. Researchers are studying the ocean's involvement in the exchange of heat, water vapor, and momentum; sequestering heat at depth; and exchange and cycling of greenhouse gases and other biogeochemically important compounds. Because of its broad focus - and because the ocean is such a vital part of the Earth system - the Section encourages dialogue with interdisciplinary scientists at the Spring and Fall Meetings and the biennial Ocean Sciences Meeting, which is jointly organized with other societies concerned with studying marine problems.