Woods Hole Engineer Examines Climate Change Impact on Ocean Sounds

WOODS HOLE – After Woods Hole Oceanographic Institution’s acoustic engineer Lee Freitag discovered stark changes in the Arctic Ocean’s Beaufort Sea two years ago, the U.S. Navy wanted to know more.

Climate change has affected many aspects of the ocean, including temperature, sea level and where certain creatures live.

But Freitag found that sound may travel further as a result of changing conditions.

The Navy, whose submarines communicate through underwater sound waves, decided to invite an ocean acoustics team from the Massachusetts Institute of Technology (MIT) to the Beaufort Sea to take more precise measurements.

They sent an underwater drone down three layers of water. The first layer, 50 to 80 meters deep, has existed previously only in the summer months and is typified by its relative warmth. Thanks to climate change, however, crews have found this layer to be permanent and warmer than before.

The second layer, a colder one, is sandwiched between the top layer and a third warmer one. The third layer stays warm from heat flowing into the Arctic Ocean from the Pacific, according to a Yale University oceanographer.

Underwater sound bends toward colder temperatures, but when sandwiched between two warm layers, it can travel further than it could previously. Sounds that used to peter out after 100 kilometers can now be detected 400 kilometers away in this part of the ocean.

The effect is called the Beaufort Lens, and scientists are still trying to figure out how far into the ocean it extends.

The group should be back in the area for more tests in 2018.

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