Scientists at the Universit´e de Lyon have found new answers to a phenomenon called “Dead Water”. No this not refer to the newly released WWII movie of the same name, rather it’s a term for the effect seen when a vessel moves through water consisting of two or more layers with different salinity. This problem is typically seen when runoff from a melting glacier forms a relatively thin layer of fresh water on top of denser seawater and results in the loss of vessel speed and steerage.
The magazine New Scientist writes:
Physicist Thierry Dauxois and colleagues from the University of Lyon found that a hidden wave at the interface of the layers invisibly chases and slows a boat (see video, top right).
The toy boat is pulled across the 300-centimetre tank with a constant force by a cable. The water is separated into two layers of different saltiness and hence density, labelled with dye.
Just as described by people who have experienced dead water in the real world, the water’s surface is smooth, but the boat suddenly slows as the concealed wave makes contact.
“It creates a depression below the boat that prevents it from moving,” team member Matthieu Mercier told New Scientist.
The scientists further state this might have been the primary factor resulting in the loss of Norwegian explorer Fridtjof Nansen and his ship Fram. The team, however, has yet to explored the link between the effect and a high number of recent cruise ship sinkings in Antarctica but it does makes sense.
One primary reason for these incidents is the growing popularity of Eco-Tourism which includes touring the Antarctic. For a long period of time this segment of the cruise ship market was dominated by small to medium sized vessels but in recent years large vessels have entered the region forcing small operators to differentiate their services by getting closer to the ice packs and taking more risk. The results have been tragic.
The following video was put together by New Scientist to help explain the phenomenon.
A briefing on the preliminary research can be found HERE.