"KODIAK ISLAND, Alaska — Forces profound and alarming are reshaping the upper reaches of the North Pacific and Arctic oceans, breaking the food chain that supports billions of creatures and one of the world’s most important fisheries.
In the last five years, scientists have observed animal die-offs of unprecedented size, scope and duration in the waters of the Beaufort, Chukchi and northern Bering seas, while recording the displacement and disappearance of entire species of fish and ocean-dwelling invertebrates. The ecosystem is critical for resident seals, walruses and bears, as well as migratory gray whales, birds, sea lions and numerous other animals.
Historically long stretches of record-breaking ocean heat and loss of sea ice have fundamentally changed this ecosystem from bottom to top and top to bottom, say researchers who study its inhabitants. Not only are algae and zooplankton affected, but now apex predators such as killer whales are moving into areas once locked away by ice — gaining unfettered access to a spoil of riches.
Scientists describe what’s going on as less an ecosystem collapse than a brutal “regime shift” — an event in which many species may disappear, but others will replace them."