Sea-Change Due to Global Warming

A recent interesting communication upgrade states that global warming may give Earth's oceans the same hi-fi sound qualities they had more than 100 million years ago, during the Age of Dinosaurs.

Global temperatures directly affect the acidity of the ocean which in turn changes the acoustical properties of sea water.

It is known that whales vocalize in the low frequency sound range that is less than 200 Hz and the this research suggest that by the year 2100 the salt water will get acidified due as a result of global warming and this will make the low frequency sound near the ocean surface to travel farther than it currently does.

The lead scientist of this study is the Rhode Island acoustician David G. Browning.

He explains the sea change this way: "We call it the Cretaceous acoustic effect, because ocean acidification forced by global warming appears to be leading us back to the similar ocean acoustic conditions as those that existed 110 million years ago, during the Age of Dinosaurs."

For the study they analyzed the historic levels of boron in seafloor sediments in order to reconstruct ocean acidity for the past 300 million years. With the help of boron's sound absorption traits and impact on low-frequency transmission, Browning and his colleagues were able to predict the soundscape of ancient oceans to conclude that 300 million years ago, during the Paleozoic, the low frequency sound transmission in the ocean was similar to conditions today.

Apart from this they also discovered that transmission improved as the ocean became more acidic, reaching its best transmission value around 110 million years ago thereby permitting the frequency sound to travel twice as far.

"This knowledge is important in many ways," notes Browning. "It impacts the design and performance prediction of sonar systems. It affects estimation of low frequency ambient noise levels in the ocean. And it's something we have to consider to improve our understanding of the sound environment of marine mammals and the effects of human activity on that environment."

Browning will present his findings at the 164th meeting of the Acoustical Society of America (ASA), held Oct. 22 -- 26 in Kansas City, Missouri.