Researchers found the sounds of bubbles gushing out of melting glaciers are much louder than previously believed, making fjords some of the noisiest places in the ocean.
A recent study looked at noise levels in the waters near Alaska and Antarctica, and discovered they were high enough to influence the behavior of local harbor seals, the University of Alaska Fairbanks reported.
"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," said Erin Pettit, a glaciologist from the University of Alaska Fairbanks Department of Geosciences.
To make their findings, the researchers looked used underwater microphones to record the average noise levels around glacier flows. They looked at fjords in three locations: "Icy Bay, Alaska; Yakutat Bay, Alaska; and Andvord Bay, Antarctica." The researchers determined the average underwater water noise level in these regions exceeded what would be heard from other major marine noise sources, such as weather, fish movement, and ships and sonar devices.
These incredibly loud sounds are believed to be generated when air trapped within the glaciers escapes rapidly, forming bubbles in the water that pop. The researchers believe this phenomenon is only going to get more intense as climate change increases the rate at which these glaciers melt; but once these glaciers begin retreating onto land the process (and sounds) will immediately disappear.
The researchers noted that these types of fjords are "foraging hotspots" for seabirds and marine mammals, including harbor seals. Seals may even use them as "hiding spots" from predatory killer whales, which use their sense of hearing to locate prey. This could explain why harbor seal populations are already declining in fjords where the glaciers have already retreated onto land.
The findings were published in a recent edition of the journal Geophysical Research Letters.
