On this day in history,...
...in 1955, the first successfully operating Swallow float was deployed, marking a major advancement in oceanographic instrumentation. Developed by John Swallow, these were the first freely drifting subsurface floats capable of measuring ocean currents below the surface, using an innovative design and ballasting system that allowed them to maintain a specific depth.
Prior to the development of Swallow floats, most ocean current measurements relied on surface drifters or indirect methods, such as geostrophic calculations. Swallow’s innovation provided direct observations of subsurface currents, greatly improving the understanding of deep ocean circulation. The floats were designed to be neutrally buoyant, drifting with the surrounding water masses, while an acoustic signaling system allowed researchers to track their movements over time.
The successful deployment of Swallow floats in 1955 laid the foundation for modern Lagrangian drifters, influencing the development of SOFAR floats, RAFOS floats, and Argo floats used in contemporary oceanographic research. These pioneering instruments contributed significantly to the study of deep ocean dynamics, eddy transport, and large-scale circulation patterns.
While this date marks the first confirmed operational success, Swallow’s work continued to evolve, leading to further refinements and broader applications of neutrally buoyant drifters in oceanography.
Sources
- Swallow, J. (1955). A neutral-buoyancy float for measuring deep currents. Deep Sea Research, 2(1), 66-81. DOI: 10.1016/0146-6313(55)90037-X
- Rossby, H. T. (1985). John Swallow and the development of neutrally buoyant floats. Progress in Oceanography, 14, 447-459. DOI: 10.1016/0079-6611(85)90025-4
- https://www.ukargo.net/about/float_history/first_floats/