Decades ago, Arthur C. Clarke envisioned an "underwater telescope" that would allow users to look down from the surface of the ocean, into its inky depths. Well, such a capability has come a step closer to reality, utilizing existing technology.
Ordinarily, when scientists wish to monitor ecologically important phenomena such as marine algae blooms, they utilize photos taken by satellites. According to researchers at Maine's Bigelow Laboratory for Ocean Sciences, however, satellite cameras can typically only "see" about five to 10 meters (16 to 33 ft) down into the sea.
Looking for a better alternative, a Bigelow team led by Dr. Barney Balch turned to ship-mounted LiDAR (Light Detection and Ranging) units.
More commonly seen on things like robots and self-driving cars, LiDAR devices work by emitting laser beams, then measuring the exact amount of time it takes for that light to be reflected back off of any objects. In this way, it's not only possible to detect the presence of obstacles, but also their distance from the user, and their contours.
Working with colleagues from Virginia's Old Dominion University, Balch's team utilized the technology on a 2018 research cruise in the Gulf of Maine. Doing so, they were successfully able to gather information on a bloom of coccolithophores, which are a type of algae.
The organisms surround themselves with protective calcium carbonate plates, which scatter reflected light in a distinctive manner. Therefore, by analyzing the reflected laser light, the scientists were able to ascertain that the algae was present, and in what amounts.
In fact, it turned out that the region was experiencing its largest bloom of coccolithophores within the past 30 years. And by using LiDAR, it could conceivably be possible to see up to three times deeper than would be the case using satellite photos.
The technology has since been successfully tested in other areas, such as the Sargasso Sea and the coast of New York City. It is hoped that LiDAR could ultimately allow scientists to quickly, cheaply and easily gather oceanographic data, without having to stop their ships in order to gather deep water samples.
"Harnessing a tool that lets us look so much deeper into the ocean is like having a new set of eyes," says Balch.
The research is described in a paper that was recently published in the journal Applied Optics.
Source: Bigelow Laboratory for Ocean Sciences
Is LiDAR in this circumstance hindered by the same ocean conditions that hinder SONAR? In that the density of the different layers of water affect the sound waves travel times which skews the SONAR's accuracy and penetration capabilities? I know lasers are light, and light speed is exponentially faster, but anyone who has tried to pick up a penny off the bottom of a pool knows your eyes deceive you....is LiDAR hampered by the refraction differences of the ocean currents and density changes?
Not to read more into this article than there is here, but Arthur C. Clarke's underwater telescope is not actually here as the statement "a step closer to reality". Yes, it is better than relying on satellite images and can probably be married to satellite imagery for even more information - but what are the limitations of LiDAR in the ocean, as we say in medicine - in vivo? But a great use of LiDAR, and thank for the synopsis.