Marine Mammals and Noise in the Arctic
A recent media piece on noise in the Arctic was published online in Arctic Deeply. SEA Senior Scientist and close colleague Chris Clark of Cornell were among those featured in the article about the science and traditional knowledge of sound and mammal behavior in the Arctic. The link is below as well as several excerpt from the piece.
Marine Mammals Unsettled as Arctic Noise Grows
February 19th, 2016 by Cheryl Katz
Industrial noise from ships, offshore development and military activity is exposing Arctic marine mammals to unprecedented amounts of man-made racket. With the retreat of the sea ice, scientists figure the Arctic Ocean will only get louder. Can they muffle the din?
Marine mammals, such as whales, rely on acoustic signals to forage, navigate, find mates and guide other key behaviors. The excess noise from human activities shrinks these animals’ acoustic habitat – the underwater area in which they are able to communicate – and this can hinder reproduction and jeopardize the population’s survival.
The problem can be especially pronounced in the Arctic, where the noise is heightened by the uniformly cold temperature of polar waters. Sound travels over longer distances and is closer to the surface in the Arctic than in temperate oceans – relaying noise across the same depths at which Arctic marine mammals spend most of their time. As a result, noise from a ship engine can be heard dozens of kilometers away and blasts from seismic airgun arrays, which fire several loud pulses a minute to map the ocean floor for oil and gas deposits, are audible for hundreds of kilometers.
“The sound scenes that we’re imposing on the Arctic Ocean are profoundly huge,” said Christopher Clark, a bioacoustics researcher at Cornell University in Ithaca, New York, who has studied bowhead whales in northern Alaska for more than 30 years. The underwater noise levels from airguns, ships and offshore construction can be several times higher than the loudest natural background sounds. “The Arctic situation is critical because man-made noise activities have been relatively infrequent” until fairly recently, Clark said.
Silenced Songs and Thwarted Migration
The effect of noise on marine mammals is determined by a complex interplay of factors. Pitch, frequency, ambient conditions, distance, whether the sound source is moving and other specifics all influence an animal’s response to sound, said Brandon Southall, a bioacoustics researcher at U.C. Santa Cruz and the former director of the U.S. National Oceanic and Atmospheric Administration’s ocean acoustics program.
For example, bowhead whale communication can be disrupted by relatively low noise levels in two distinct ways depending on the total amount of sound they receive over time. A recent study published in the journal PLOS One looked at the reaction of bowheads in the Beaufort Sea to noise from airguns during oil exploration from 2007 to 2010.
But other activities, such as military operations by nations with Arctic borders, appear to be ramping up. And ship traffic will likely increase in places as the sea ice continues to recede.
“I think we’ve learned enough, and there’s been enough responsible development, that it can be done in ways that minimize the effects,” said Southall. For starters, governments could restrict noisy activities during the spring when females with calves are present, and enforce “exclusion zones” that require airguns to stop if species such as bowheads or beluga come close.
“There’s some informed and adaptive ways,” Southall said. “But they need to be supported in a combination of science and traditional knowledge.”