[1] Of Scandinavian ancestry, Johnson was born on September 30, 1893, in a sod-roofed farm house on the Great Plains in Chandler, South Dakota.

[1] With Harald Sverdrup and Richard H. Fleming, Johnson wrote The Oceans: Their Physics, Chemistry and General Biology, considered a landmark reference work.

[2] Johnson proposed an explanation for the deep scattering layer (DSL), a puzzling phenomenon observed by Navy sonar during World War II, in which the depth of the ocean appeared to change.

Johnson and the Scripps graduate students studied the California Current and did fundamental research to establish the nature and life histories of zooplankton populations.

This work led to a "heretical" theory, supported by further research, that the physics of water movement was an important factor underlying explanations of population biology and community diversity.

It was the first Scripps expedition to use scuba divers to explore the Pacific, and also used techniques such as echo sounding, seismic and magnetic data collection, coring and heat flux measurement.

[6][7][8] After his "retirement", as a professor emeritus, Johnson studied the larval development of Pacific lobsters and identified differing developmental sequences.

[1] The National Academy of Sciences in 1959 awarded Johnson the Alexander Agassiz Medal, "For his outstanding leadership in biological and general oceanography.