How these connect

Retreating bright ice exposes dark ocean that absorbs more solar energy - the ice-albedo feedback is a principal contributor, though the lapse-rate feedback and changes in poleward heat transport also contribute and their relative weight is contested.

Juveniles shelter and feed at the underside of the ice and in its cracks, which makes the ice a nursery rather than merely a cover.

Coastal foxes range far onto the winter pack ice, scavenging polar bear kills and crossing between landmasses over it; a tracked Svalbard animal reached Ellesmere Island in about seventy-six days.

It is the only vertebrate that breeds on sea ice: the landfast ice under the colony must hold from laying in the winter dark until the chicks fledge in spring.

Emperors take krill along with fish and squid; almost every Southern Ocean vertebrate is within one or two steps of the same crustacean.

The colony failed from 2016 because the fast ice it stood on broke out before the chicks could fledge, in successive seasons.

The algae live inside the brine-channel network of the ice and on its underside; without the ice as substrate the community has no habitat.

The dependence is a life-history one rather than a preference: larval survival through the austral winter is tied to the presence and duration of the pack ice.

Krill larvae overwinter beneath the pack ice grazing the algal layer on its underside, which is why winter ice extent sets recruitment.

The bear hunts from the surface of the ice; where and when the ice is absent it cannot reach seals at all, which is why the IUCN identifies sea-ice loss as the principal threat to the species.

The ringed seal is the polar bear's principal prey across most of its range, taken at breathing holes and by breaking into birth lairs.

A polynya is defined by the ice around it: it is a persistent opening within a sea-ice cover, not simply open water.

It maintains breathing holes through thick fast ice with its foreflipper claws and pups in a lair excavated in the snow drift above the hole; both stable ice and sufficient snow are required.

Arctic cod is the principal energy transfer from ice-associated invertebrate production to seals and seabirds in much of the Arctic.

It breeds on landfast ice and holds breathing holes open through the winter with its teeth, which is what lets it use ice no other large predator can.