Ocean scientists have discovered something baffling yet interesting in the Caribbean Sea. One region in the ocean behaves like a whistle in the middle of the oceanic noise. It is a powerful whistle that can be heard and captured in space like oscillations of the earth's gravity field, though it cannot be heard by humans.
Ocean scientists from the University of Liverpool, Chris Hughes and colleagues, heard the whistling when they were examining ocean dynamics in the Caribbean Sea. In their analysis, they pinpointed a peculiar trait in the pressure oscillations.
The size of the sea made the sound emerge from the seafloor. The note was that of A-flat, even though there were many octaves that were much lower than a piano and could not even be heard.
"We were looking at ocean pressure through models for quite different reasons, and this region just didn't work. It felt like a sore thumb," Hughes told Gizmodo.
Scientists discovered that the mystery pressure oscillations tend to happen in life, without just showing up in the models. Due to the low noise that was produced, it was described as a whistle.
This "Rossby Whistle" can be heard with the large Rossby waves that push to the west and interact with the seafloor, which generates the whistling sound.
"We can compare the ocean activity in the Caribbean Sea to that of a whistle," says Hughes. "When you blow into a whistle, the jet of air becomes unstable and excites the resonant sound wave which fits into the whistle cavity. Because the whistle is open, the sound radiates out so you can hear it."
Researchers say that the waves appear again on the eastern side of the basin 120 days after they vanish in the west. Thus, the water sloshes in and out of the basin and interacts with the seafloor.
"The porous boundary of the Caribbean Sea results in this mode, exciting a mass exchange with the wider ocean, leading to a dominant mode of bottom pressure variability," the study reports.
As it is a huge exchange, it is strong and brings about changes in the gravitational field around the earth. Satellites can measure the gravitational waves.
"An ocean current flowing through the Caribbean Sea becomes unstable and excites a resonance of a rather strange kind of ocean wave called a 'Rossby wave.' Because the Caribbean Sea is partly open, this causes an exchange of water with the rest of the ocean which allows us to 'hear' the resonance using gravity measurements," Hughes said
The study was published in the journal Geophysical Research Letters,
