Underwater rivers along the Australian coast found using AUVs
River systems exist all around us. The Charles River, the Mississippi River, and the Colorado River are just a few that come to mind. However, in recent years, scientists have begun to find a similar water flow undersea (1). Undersea rivers share many characteristics with standard rivers.
Underwater rivers near Australia were found using Autonomous Underwater Vehicles, or AUVs. AUVs are typically equipped with temperature sensors, motion monitors, salinity readers, and cameras. They do not need to be connected to a larger ship while at sea because they operate autonomously (2). While many AUVs are unable to communicate in real-time with programmers, they are still able to send satellite signals or messages every so often (3). The simplest of these vehicles are shaped like torpedoes, whereas more advanced vehicles called gliders have propellers. AUVs are capable of operating in both very shallow and deep water, meaning they have utility in a variety of environments (4).
The first underwater river was discovered using an AUV in 2010 by British scientists in the Black Sea (5). The AUV was able to detect not only the basic path of the river but clear banks and waterfalls within the river. This discovery demonstrates the importance of using AUVs to gather detailed information and map the seafloor.
Underwater rivers are phenomena that occur irregularly in seas globally (1). They form as a result of density differences or heat differences in seawater (6). In warmer months, coastal areas receive less freshwater because of evaporation, increasing the salinity of the surrounding ocean. In the fall and winter, the salty and shallow water cools, making it denser. High density water on the continental shelf, the submerged part of a continent, then sinks and is pushed further from the shore. Water begins to flow on the ocean floor out to sea. This dense water also disturbs sediment, carrying it in its flow (7).
Most marine animals do not live in areas with high-current underwater rivers, but small invertebrates, such as snails, clams, crustaceans, urchins, sea cucumbers, and worms, are able to survive (1).
Between 2008 and 2019, the University of Western Australia, affiliated with Australia’s Integrated Marine Observing System, situated AUVs at 8 locations along the coast, using over 126 vehicles (7, 8). The data collected on salinity, density, and temperature was a key part of research in finding this river network all along Australia’s continental shelf. Drastically more rivers were discovered in winter months, as opposed to summer (9).
Australian underwater rivers are the largest spanning network of underwater rivers discovered globally. The network covered over 6,000 miles. While underwater rivers have been found across the world, this is by far the largest network of such rivers discovered yet.
Underwater rivers are key in transporting nutrients from the coast to the deep sea. Understanding this phenomenon is crucial to knowing how pollutants, too, can be dragged deeper into the ocean from pollution and garbage sites on land (10). This unique discovery may in fact pave the way for many more studies to follow.
Caption: An AUV lowered into the water
Caption: The continental shelf, shown above, is where underwater rivers begin to form.
1 Gray, R. (2019). The giant undersea rivers we know very little about. Retrieved October 6, 2022, from https://www.bbc.com/future/article/20170706-the-mystery-of-the-massive-deep-sea-rivers.
2 What is an AUV? What is an AUV? : Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research. (n.d.). Retrieved October 4, 2022, from https://oceanexplorer.noaa.gov/facts/auv.html.
3 AUVs. Woods Hole Oceanographic Institution. (2019, January 23). Retrieved October 4, 2022, from https://www.whoi.edu/what-we-do/explore/underwater-vehicles/auvs/.
4 Wynn, R. B., Huvenne, V. A. I., Bas, T. P. L., Murton, B. J., Connelly, D. P., Bett, B. J., Ruhl, H. A., Morris, K. J., Peakall, J., Parsons, D. R., Sumner, E. J., Darby, S. E., Dorrell, R. M., & Hunt, J. E. (2014, March 22). Autonomous underwater vehicles (AUVs): Their past, present and future contributions to the Advancement of Marine Geoscience. Marine Geology. Retrieved October 10, 2022, from https://www.sciencedirect.com/science/article/pii/S0025322714000747.
5 What are underwater rivers and how were they discovered. WeatherAPI.com Blog. Retrieved October 21, 2022, from https://blog.weatherapi.com/2019/04/what-are-underwater-rivers-and-how-were-they-discovered.
6 Scientists discover unusual underwater rivers along Australia’s coastline : Archive Page : The University of Western Australia. (2020). Retrieved October 6, 2022, from Uwa.edu.au website: https://www.news.uwa.edu.au/archive/2020061712167/research/scientists-discover-unusual-underwater-rivers-along-australias-coastline/.
7 US Department of Commerce, N. O. and A. A. (2011, July 5). The depths below – lakes in an Ocean. Ocean Today. Retrieved October 10, 2022, from https://oceantoday.noaa.gov/lakesinanocean/.
8 Network of Underwater Rivers Found Off Australia’s Coast. (2020). Retrieved October 6, 2022, from Sport Diver website: https://www.sportdiver.com/network-underwater-rivers-found-off-australias-coast.
9 staff, S. X. (2020, June 17). Scientists discover unusual underwater rivers along Australia’s coastline. Phys.org. Retrieved October 10, 2022, from https://phys.org/news/2020-06-scientists-unusual-underwater-rivers-australia.html.
10 News archive. Scientists discover unusual underwater rivers along Australia’s coastline : Archive Page : The University of Western Australia. (n.d.). Retrieved October 10, 2022, from https://www.news.uwa.edu.au/archive/2020061712167/research/scientists-discover-unusual-underwater-rivers-along-australias-coastline/.