GPS drifters unlocking the secrets of rip currents
To get inside the heart of rips we followed Dr Brander as he used mobile devices called drifters that are fitted with GPS trackers. These drifters helped Rob study the flow direction and flow speed of rip currents and have been used by many other rip current scientists around the world.
The data from these drifters has revealed an enormous variability in how rips flow and circulate. Typically rips are about 10 to 50 meters wide and can flow anywhere from 10 to 100 meters offshore. But not always. Rob has measured some rip currents that have flowed 400 metres offshore.
Drifter research has also revealed that sometimes rips flow well beyond the surf zone out into deeper water and other times they recirculate within the surf zone as rotating eddy’s. What makes rip currents even more dangerous is that their behaviour can quickly change from one flow direction to another.
Faster than an Olympic swimmer
While most rips typically flow at speeds of 0.3 – 1 meter per second, which is faster than many people can swim, they can also suddenly pulse, or quickly accelerate in speed, in response to larger breaking waves, which causes them to flow as fast as 2 meters per second – which is Olympic swimming speeds.
