Arctic and Antarctic

In the Antarctic the picture is more complex, but two major ice shelf collapses over the last decade may be a sign of what's to come.

Other warming signs:

• In the Arctic, ice thickness has declined by over 40 percent, andan area larger than the Netherlands is disappearing every year.Scientists predict Arctic sea ice could melt entirely within 70years.   
• The Greenland ice sheet - the biggest ice mass in the Northern Hemisphere - is losing mass from glacier discharge and accelerated summer melting and runoff.  
• Melting permafrost is causing trees and buildings to fall downin the far North. Almost a quarter of all land in the Northernhemisphere has permafrost under it. As it melts, carbon dioxide andmethane stored in the ground is released.
• The warming in parts of Antarctica has already contributed to a decline of some Adélie and emperor penguin populations.

The consequences of warming

Thewhole Arctic marine ecosystem is tied to the presence and dynamics ofsea ice. The Arctic marine food chain begins with ice algae that clingsto the underside of the ice pack all winter, and creates a dense matunder the ice in spring. Some arctic species travel halfway around theworld to exploit the food sources that flourish along the edge of themelting ice.

Removing this dynamic would have profoundconsequences for all Arctic life. If the sea ice is drastically reducedor the timing changed, we can expect the loss of many species that arereliant upon this special habitat.  

Some Arctic animals that depend on sea ice

• Walruses, which travel long distances on floating sea ice thatallowing them to feed over a wide area, may be particularlyvulnerable.  In a warmer future, sea ice will likely melt rapidlyin the spring, shrinking quickly over continental shelf areas andwithdrawing to the deep ocean of the central Arctic. This could bedevastating to walrus, as females  use sea ice as a platform fromwhich to feed their young and teach them to feed, primarily onshellfish from the bottom of shallow continental shelf areas.
• Many species of seal are ice-dependent, including thespotted seal, which in the Bering Sea breeds exclusively at the iceedge in spring; the harp seal, which lives at the ice edge all year;the ringed seal, which give birth to and nurse their pups on sea ice;the ribbon seal; and the bearded seal.
• Polar bears would be threatened by any decline in ringedseal populations, their main food source. Moreover, polar bears aredependent on sea ice for hunting and transportation. The polar bears inHudson Bay and James Bay already fast during the four ice-free summermonths they are forced to spend ashore, and pregnant females fast foreight months.  The extension that has already been observed inthis ice-free period has already resulted in  decreased birthrates and will sooner rather than later lead to starvation andultimately the extinction of local polar bear populations.  
• Sea ice also plays an important role in the Antarcticecosystem, particularly as habitat for sea ice algae, the primary foodsupply for larval krill over winter.   Krill are vital to theAntarctic food chain.  Penguins, fish, sea lions, seals and manyother full time Antarctic residents rely on the ice ecosystem. Minke whales travel from half the world away to feast on the krillevery spring.      

Shrinking ice threatens people and communities