Melting glaciers create some of the noisiest areas in the ocean, according to new research. Bubbles rising from the features create a great deal more noise in aquatic environments than researchers had previously estimated.
Fjords and icebergs in waters off the coasts of Alaska were examined, using underwater microphones. Measurements were taken in Andvord Bay, Antarctica, as well as Yakutat Bay and Icy Bay in Alaska. Each area features glaciers flowing into ocean fjords. Researchers found that noise created by bubbles generated by melting glaciers was greater than that from all other sources combined, including animal communication and movement, weather and ships.
The effect of this noise on marine wildlife, including whales and harbor seals, is unknown. However, the recordings show the bubbles create noises with frequencies as low as 30 Hertz, almost five octaves below middle C, up to 20,000 Hertz, the highest note which can be heard by humans.
"The ocean ambient sound gives us clues to the physical processes going on, but it also is an important aspect of the environment in which marine mammals and fish live. Like teenagers at a loud rock concert, the seals and whales modify their behavior depending on the ambient sound levels," Erin Pettit, a glaciologist from the University of Alaska Fairbanks, said.
Seals could use the noise to their advantage, hiding from killer whales that depend on natural sonar to locate their prey.
As glaciers melt under water, the process releases vast quantities of air which had been trapped within the ice. This forms bubbles that burst apart as they rise in the water, creating vibrations which are heard as noise in the marine environment. This sound is much like that of a babbling brook, but the effects of the phenomenon could be severe.
Fjords with glaciers play a vital role in the wildlife environment. The features provide breeding grounds for harbor seals, as well as acting as a hunting grounds for marine mammals and seabirds.
Global climate change, including global warming, is resulting in receding glaciers. As these features disappear from the oceans and retreat onto land, the seals may be losing the acoustic protection provided by glaciers. This could account for a recent reduction in their populations in these regions, researchers speculate.
Future research which could be carried out in light of this finding includes studying whether the pattern of sounds can be used to predict melting. Additional examinations will also be made to determine the effect of the noise on local ecosystems.
The study examining the sound of bubbles from melting glaciers and early analysis of its effects, was profiled in the journal Geophysical Research Letters.
