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Is most of the ocean unmapped and unexplored?
Oceans cover more than 70% of our planet and are predicted to be home to more than 2 million marine species. According to the U.S. Geological Survey, there is over 332,000,000 cubic miles of water in the sea, so it is not surprising that we haven’t yet explored our oceans in their entirety. It is often said that we know more about the highest mountain peaks (or even the surface of the moon and Mars!) than our oceans, but is this true? We asked 7 experts in oceanography, marine biology and ecology ‘Is most of the ocean unmapped and unexplored?’, here is what they said…
Is most of the ocean unmapped and unexplored?
How do we explore our oceans?
There are many types of ocean exploration such as: measuring the sea depth, mapping the seabed or surface, or recording what living things are found there.
Mapping the seabed, sea surface and measuring sea depth can be done with satellites. Dr Douglas Fenner, an expert in marine biology from the National Oceanic and Atmospheric Administration in the USA, says “modern satellites can map the ocean floors... They can do it by measuring the height of the ocean (probably with radar). When there is an undersea mountain, that mountain has mass that gravitationally attracts water, making the water surface just slightly higher above the mountain. The opposite is true of trenches. And the height of sea floor in between those can and has all been mapped.” Satellites are not the only approach, however. Dr Fenner adds “The more traditional way to measure and map the seafloor is by sonar. A ship sends out ‘ping’ sounds as it moves along, and records the time it takes for the ping to bounce off the floor and return. That produces a detailed map of the bottom.”
Dr Fenner says recording marine species can be achieved “by trawling, or by mud ‘grabs’ or sediment mapping with sediment cores”. Alternatively, videos and images can be taken to identify which species lurk under the waves, and to learn more about their biology and behaviour.
How much of our oceans have we mapped?
Mapping the sea surface is much easier than identifying which species of fish live under it. These differences are reflected in how much we have explored these different aspects of the ocean.
Modern satellites have mapped the sea surface everywhere, but do not give us very detailed information. For scale, mapping of the ocean floor is done at a resolution of 5 kilometres, whilst maps of the surface of planet Mars have a resolution of 20 meters! Dr Fenner says [Sonar] “has greater resolution than the satellites, but it can only cover where the ship is. Some ships leave their sonar running as they go about their business steaming to different places. If you look at Google maps, and magnify the image of seafloor, you will see stripes of sharper resolution where ships have gone.” Professor Jessica Meeuwig, an expert in marine science and ecology from Western Australia University, adds that “As of 2021, less than ten percent of the global ocean has been mapped using modern sonar technology. Most of what is mapped is also near shore and in relatively shallow waters (<200 m).” So, the seabed has been mapped to a low resolution everywhere (using satellite), but to a higher resolution only in certain places (using sonar).
Megan Cook, an expert in oceanography from the Ocean Exploration Trust in the USA, says “Today only 20% of oceans deeper than 200 meters are mapped in high-resolution (for more info and annual updates visit GEBCO Seabed 2030 Project). And less than 5% of oceans have been visually surveyed due largely to the scale of the ocean. The average ocean depth is around 3.9 km or almost 13,000 feet. Scientists agree that most deep-sea animals are yet-to-be-discovered.” Dr Fenner adds that “Biological mapping … can only map very small points or areas, so has not been done everywhere. Likewise, imaging life on the seafloor requires putting down cameras and can only be done in very small areas. Plus, at great depths, it is difficult to make camera housings that can withstand the pressures.”
Professor Martine Lizotte, an expert in oceanography from Laval University in Canada, summarises that “While estimating the actual percentage is challenging and a matter of debate, the National Oceanic and Atmospheric Administration (NOAA) suggests that more than 80% of the oceans remain unexplored to this day.”
Why is so much ocean still unexplored?
In terms of seafloor mapping, Dr Rodrigo Garcia del Campo, an expert in ecology from the National Biotechnology Centre in Spain, says “it is really difficult to cartograph the bottom of the oceans. We would need to use sonars and boats that would have to travel all oceans”. In terms of biological mapping, the low-throughput approach makes it difficult to map such huge areas. Additionally, Professor Lizotte says that the reason we haven’t explored most of the ocean “is explained by the challenging environmental conditions (particularly high pressures at depth) and tremendous costs associated with the exploration of the deeper oceanic realm.”
How can we map these unexplored parts?
Technological advances play an essential role in improving our ability to map and explore the ocean. Professor Lizotte says “The advent of modern sonar technologies that help in mapping the seafloor and the use of remotely operated vehicles (ROV) or autonomous underwater vehicles (AUV) that scan the water column has increased our observations. The international ARGO program, consisting of a fleet of robotic instruments that drift with the ocean currents and move up and down between the surface and the first 2000 m of the water column, has also led to a greater spatial and temporal coverage of oceanic waters.”
Professor Lizotte concludes that “In a sense, oceans represent the great frontier for the next generation of explorers and researchers, where vast opportunities for inquiry and investigation remain.”
Most of the ocean remains unexplored in terms of high-resolution exploration and biological mapping.
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