| Online: | |
| Visits: | |
| Stories: |
Melting glaciers create noisiest waters on Earth
Brett Smith for redOrbit.com – @ParkstBrett
You might think that the noisiest parts of Earth’s oceans are the shipping lanes near busy American or European ports, but you’d be wrong. Thanks to rapidly melting, shearing and calving ice sheets, the waters near Alaska and Antarctica are actually the noisiest waters known to man, according to a new study in Geophysical Research Letters.
Upon finding out just how loud these waters are, the study team said their thoughts immediately shifted to the bay seals and other creatures that rely these regions for food, shelter and mating.
[STORY: This is what an upside down iceberg looks like]
“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,” said study author Erin Pettit, a glaciologist from the University of Alaska, Fairbanks. “Like teenagers at a loud rock concert, the seals and whales modify their behavior depending on the ambient sound levels.”
Glacial calving < air bubbles
In the study, the team used marine microphones to listen to and document the average sound levels in three coves where glaciers flow into ocean fjords: Icy Bay, Alaska; Yakutat Bay, Alaska; and Andvord Bay, Antarctica. Every one of the fjords has numerous icebergs from glacial calving.
[STORY: Greenland wasn't always covered in ice, study finds]
The scientists learned that the average underwater noise level from bubbles in these fjords surpassed levels made by other sources, which include weather, the motions and communications of fish, and man-made machines like ships and sonar units. The team assessed sound waves at frequencies between 300 and 20,000 Hertz, which includes most of the average human’s hearing range.
Glacial calving added to some of the underwater noise, but the loud sounds caused by the process were temporary. It was the steady melting of ice from the glaciers and their icebergs that was the true noise generator. Air trapped inside the glacier ice leaves rapidly as it melts into saltwater, developing bubbles in the water that pop as they leave the ice.
How this affects wildlife
Pettit said the team’s conclusions raise questions on how the underwater noise in the fjords will impact animals as climate change boosts the rate at which glaciers disappear into the ocean and then halts the process entirely as the ice sheets retreat onto land.
[STORY: Strange 'pancake ice' appears in Scotland]
Pettit said fjords with glaciers are feeding hotspots for seabirds and marine mammals, in addition to being crucial mating locations for harbor seals. Seals could use the underwater noise to help hide from killer whales, which listen to find their prey, she added. As glaciers shrink back onto land, the seals would lose their acoustic camouflage, which could reveal why harbor seal populations are diminishing in fjords where glaciers have shrunk back onto land.
The team said that further research studies are required to investigate the connection between the underwater noise levels and the fjord environments. The team will keep listening to glaciers to see if they can create a method of forecasting glacier melt based on the record of underwater noise.
—–
Follow redOrbit on Twitter, Facebook, Google+, Instagram and Pinterest.
redOrbit.com
offers Science, Space, Technology, Health news, videos, images and
reference information. For the latest science news, space news,
technology news, health news visit redOrbit.com frequently. Learn
something new every day.”
Source: http://www.redorbit.com/news/science/1113349727/melting-glaciers-create-noisiest-waters-on-earth-031015/
