Instruments with fixed locations such as CTDs cast from a ship or surface buoys collect data by remaining in one location as ocean currents pass them by. Some instruments, like moorings and buoys, stay in one place for long periods of time to measure how conditions change in that particular location. Other instruments, like CTDs, are deployed off a ship to take measurements of ocean conditions in a particular place and moment of time. In this way, they are useful for measuring change in the ocean.
Studying the twilight zone is tricky business. It’s dark, frigid, pressures are extreme—and salty seawater corrodes metal. Many animals that live there are agile and transparent, which makes them really hard to follow and observe. To counter these challenges, OTZ scientists have developed a suite of instruments and robots, each designed to perform a particular function to shed light on this mysterious place.
Autonomous vehicles are preprogrammed to move through the water on their own, without being tethered to a ship. They can be either free-swimming like Mesobot and gliders, or move vertically through the water column like TZEx and MINIONs. Being autonomous allows the vehicles some freedom while following a particular target—be it an individual animal or a predetermined path set by scientists—but because they are not connected to a ship, their data cannot be analyzed in real time.
Towed Vehicles and Devices
Towed vehicles and devices like Deep-See, MOCNESS and ISIIS are dragged through the water by a ship at the ocean’s surface to survey an area of ocean, independent of currents. They send real-time data back to a ship at the surface through a fiber optic tether, which allows scientists to observe ocean conditions in real time, and command the vehicles from above. Because they are attached to a ship, their mobility is limited to the length of their tether, so while they are ideal for surveying general layers or areas of the ocean, they cannot follow individual animals.