By Corinne Purtill, The New York Times

Audio recordings in Arctic seas show orcas in waters that were once blocked by ice, and the effects are being felt up and down the food chain.

Brynn Kimber, a research scientist at the University of Washington who works in the National Oceanic and Atmospheric Administration’s Marine Mammal Laboratory, has spent a lot of time analyzing audio data recorded in the icy waters north of Alaska, Canada and Russia. Typically, Ms. Kimber hears the chatter of bowhead whales, belugas, narwhals and other cetaceans native to that part of the Arctic.

A few years ago, they started hearing a distinctive cry acousticians describe as similar to that of a disgruntled house cat: The piercing call of a killer whale. Ms. Kimber wondered at first if their ears were deceiving them.

“When I started the job my mentor told me, ‘You won’t see killer whales this far north,’” Ms. Kimber said. But as years of data accumulated, along with more orca calls in areas where they’d never been recorded, it appeared that was no longer true.

“Where I would see absolutely none in previous years, in later years I was seeing more and more,” Ms. Kimber said. “That was pretty unusual.”

The orca calls are further evidence of a rapidly changing Arctic. As sea ice has receded, killer whales — which are actually dolphins — are now venturing to parts of the sea that were once inaccessible, and spending more time in places they were once seen only sporadically, according to data Ms. Kimber presented Thursday at the annual meeting of the Acoustical Society of America in Seattle.

As a result, some of nature’s most effective predators have vastly broadened the scope of their hunt. The change has potentially significant consequences for animals up and down the food chain — including humans.