Resting harbour seals alongside nesting seabird colonies are drawing the hungry carnivores closer, said Joanna Sulich, a biologist with the Norwegian Polar Institute and Polar Bears International.

"In some ways, it's totally shocking," said John Whiteman, chief research scientist at conservation non-profit Polar Bears International. "What's really sobering is that these kinds of declines are the kind that unless sea ice loss is halted, are predicted to eventually cause ... extinction."

The number of viewers of TV and streaming ads for formula skyrocketed to roughly 562 million this year, up from just 200,000 last year, according to data from media measurement firm ISpotTV. Some ads came from new brands the U.S. government approved to ease the shortage. Others came from already approved brands stepping up marketing.

Danone ran the biggest of the formula campaigns this year for its Aptamil brand, recently allowed by regulators on U.S. shelves, ISpotTV found.

"Bears don't know all the negatives that come with plastic ingestion and the diseases and toxins they're likely exposed to in a (landfill) setting," said co-author Geoff York, senior director of conservation at Polar Bears International, an advocacy group.