Melting glaciers’ fizzing bubbles lead to noisy seas

Jeffrey Nystuen

Melting glaciers’ fizzing bubbles lead to noisy seas

Glaciers may look tranquil and majestic, but when they start melting they can make a real racket. A new study shows that as a glacier’s ice melts, bubbles of pressurized ancient air escape into the water, leading to noise levels even louder than those beneath rain-pounded seas heaving with 6-meter waves. Data gathered by underwater sensors at three sites where glaciers meet the sea (including a yearlong deployment of instruments in Icy Bay, Alaska, shown) reveal that the noise persists year-round and is loudest at frequencies between 1 and 3 kilohertz, more or less the pitches in a piano’s two uppermost octaves, the researchers reported online this week in Geophysical Research Letters. Melting glaciers sound a bit like radio static or white noise; click above to listen to a melting glacier. The team’s experiments suggest that the noise isn’t caused by bubbles rising through water or popping when they reach the surface. Instead, the main source of the clamor occurs when bubbles disengage from the melting glacier and suddenly spring back into their original spherical shapes after thousands of years of being squeezed by the ice. The new study offers hope that scientists could monitor the melting rates of tidewater glaciers simply by measuring underwater noise in the fjords. The findings may also explain why harbor seal populations are declining in fjords whose glaciers have retreated onto land: Without the acoustic camouflage provided by the bubble-induced din, the seals may have a harder time evading their main predator, the killer whale.