Methods thus far of locating and removing debris from the open ocean,

in short, have been unsuccessful and expensive. Removal efforts typically

involve using sea-craft to search for and locate debris, which takes time,

manpower and money. Combing the vast ocean to pluck out debris items

one at a time is simply not the answer. While one solution may be to

educate and empower consumers to limit their plastic consumption,

another option lies within the field of remote sensing. 

Through the use of in situ remote sensing data, airplanes,

drones and other airborne craft and sonar, floating debris can be

detected and removed with a lower cost than traditional methods. 

 

Current methods of using remote sensing to locate floating debris often involve matching oceanic in situ data such as chlorophyll concentrations, sea surface temperature (SST) and wind stress levels against visual sightings or recorded RGB video of floating debris. There is some work being done in using LiDAR and Thermal imaging to detect floating debris as well, but it is very limited.  In situ data is used primarily to pinpoint potential zones for the accumulation of floating debris. Ships, drones, planes and other craft are then deployed to these zones to located debris, which can then be removed by divers and specially outfitted ships. 

 

Such in situ data is used because of its unique relationship to marine debris. The locations of high chlorophyll and SST levels in the open ocean often indicate a higher level of ocean energy and activity, most often due to the presence of ocean current convergence zones, or gyres. Gyres are essentially the key oceanographic feature which powers ocean convection, or the transport of hot and cold water throughout the ocean through cold and hot water currents, like the Gulf Stream. However, the gyres not only transport water throughout the ocean but algae, planktonic animals, sediments and even floating plastics, all of which can accumulate in or around the gyres. Researchers can then create what is called a Debris Estimated Likelihood Index (DELI) and can actually predict where high concentrations of floating debris may exist in the ocean. 

 

 

The use of both side scanning and traditional sonar is also an option for the detection of marine debris. The use of sonar for this purpose is more widely used and is very effective for locating large debris such as shipwrecks or derelict fishing gear (DFG) which has sunk to the ocean's floor. Due to the high cost of using ships and sonar systems, sonar is typically used in situations where debris has been known to accumulate, or where there is some local knowledge of bottom debris. Where local knowledge exists, the process of using sonar is quite simple. Once a target's general location is known, a ship can easily navigate the area, recording the sonar data as they go. The data is then processed, where debris items such as lobster pots, sunken vessels, and cargo containers can be identified and geotagged with an exact geographic location.