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What Methods Do Scientists Use to Study the Ocean?

The world's first major voyage devoted solely to study of the ocean was the Challenger voyage in 1872. During its four-year expedition around the globe, HMS Challenger collected specimens and samples, measured temperature and salinity, and accumulated a wealth of useful data for marine scientists. Oceanography has come a long way since the Challenger, and scientists now have many tools and methods they use to study the sea, but much remains to be discovered about the world's oceans.

Satellite Imaging
- Satellites have become valuable tools for studying the ocean. The SEASTAR satellite launched by NASA in 1997, for example, uses a color scanner to measure levels of chlorophyll in surface waters; this data is important for determining ocean productivity in different regions. By bouncing radar waves off the ocean's surface, satellites can measure sea-surface contour variations and wave height, and specially-equipped satellites can monitor temperature, climate patterns, water vapor in the atmosphere, ocean surface currents and more.
Dark &Light Bottles
- Scientists often want to know how net and gross productivity vary with depth. Gross productivity measures the rate at which photosynthetic organisms in ocean water fix CO2 into organic compounds; net productivity subtracts the amount of CO2 released by respiration. One relatively straightforward way to measure both is with a cable lowered into the water column with dark and light bottles suspended on either side. Photosynthetic organisms increase the oxygen concentration and decrease the CO2 concentration in the light bottles but not the dark bottles, since the dark bottles absorb all light. Measuring the difference in concentration between the two gives scientists the data they need to calculate productivity.
Bathymetry &Ocean Composition
- Multibeam echo sounder systems bounce sound waves off the seafloor to measure the depth. Ships equipped with these sonar devices have been used to map large swathes of the ocean floor. Research ships can also take samples of ocean water and measure their composition with chemical tests. Portable salinometers lowered from the side of the ship test the salt concentration or salinity in the water. Ocean buoys are even more convenient since they can transmit data remotely, so they can offer continuous monitoring of salinity and temperature in a given region.
Tagging
- Tagging animals then returning them to the wild makes it possible to track their movements and learn about their migration patterns. If the animal is later retrieved in another location, the tag can be returned to the original lab, together with information about where the animal was found. More sophisticated tags actually detach from the animal at some pre-determined point and float to the surface, where they transmit data to the lab that deployed them. These tags can offer scientists a wealth of information about the lives of animals who might otherwise be difficult to study.

Nature