A research scientist at the University of Washington has spent a lot of time analyzing audio data recorded in the icy waters north of Alaska, Canada and Russia. The chatter of bowhead whales, belugas, narwhals and other cetaceans is heard by Ms. Kimber.
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 if their ears were telling the truth.
Ms. Kimber was told by her mentor that she wouldn't see killer whales this far north. It appeared that was no longer true as years of data accumulated, along with more orca calls in areas where they had never been recorded.
Ms. Kimber said that she was seeing more and more in later years. That was not normal.
The orca calls are evidence of a rapid change. The data presented by Ms. Kimber at the annual meeting of the Acoustical Society of America shows that killer whales are now venturing to parts of the sea that were once out of reach.
Some of nature's most effective predator have expanded their hunt. The change could affect animals up and down the food chain.
Since satellite monitoring began, the sea ice has declined. The last 15 years have seen the disappearance of 75 percent of the ice volume, and the remaining ice is thinner and of poorer quality.
The presence of orcas in the waters of the North Pole can cause Bowhead whales to travel farther to seek ice to hide in.
The loss of ice coupled with warming waters and atmospheric temperatures has affected every level of the Arctic. Large mammals like polar bears have trouble navigating shrinking habitats, while the marine algae blooms sooner and more abundant than ever before.
The behavior of the region's marine mammals has changed in recent years. Orca are more likely to eat bowhead whales. There are a growing number of bowhead whale carcasses in the northeastern Chukchi and western Beaufort seas with signs of orca attack.
Even if the orca doesn't take a bite, the presence of the predator can have far-reaching consequences. When threatened by orcas, the giant-skulled bowheads retreat into protective patches of dense ice, which lack their ability to break through frozen waters for air. The bowhead fear response evolved to avoid killer whales.
The defense mechanisms can prove to be a liability when the ice is gone. Before hiding in thick ice, bowheads must spend more time than ever. Calves that aren't strong enough to break through the ice can suffocate.
The baleen whales are a significant source of food for Inuit people in the north.
A research scientist with thearctic region of fisheries and oceans Canada said that killer whales are intelligent. They consume quickly. If a new area opens up, they can exploit a prey population that could be slow to respond to changes.
It could take years for scientists to fully understand the long-term consequences of how these extremely lethal and newly emboldened hunters are expanding their reach.
