


Caribou may be affected by changes in their food sources, as a result of the warming climate, and increased human activity along shipping routes may affect their migration. (Mark Post/Penn State University)

The proportion of the Arctic covered by sea ice during the summer hit a record low in 2012. Since 1979, the summer sea ice coverage has declined by about three-million kilometres squared, losing an area larger than the province of New Brunswick each year, scientific records show. Because dark open water reflects far less sunlight than ice, warming accelerates with sea ice loss, which in turn causes the ice to melt more quickly.

While most people see the loss of sea ice as a sign or indicator of climate change, it's far more than that, say U.S. and Canadian scientists in a paper published Thursday online in the journal Science.

Sea ice in the Arctic is analogous to trees in a forest, said Jedediah Brodie, a conservation ecologist at the University of British Columbia who co-authored the paper.

"When you cut the trees, you alter the entire ecosystem — every other species that lives in a forest in some way depends on those trees," he said in a phone interview.

'Loss of a globally important ecosystem'

The loss of sea ice is "actually the loss of a habitat," he added, "and that's the loss of a globally important ecosystem."

Sea ice plays a huge role in the Arctic because 80 per cent of the low-lying tundra is within 100 kiometres of the ocean that is covered by ice for at least part of the year.


It's most obvious that sea ice loss will affect marine organisms, but some of the specific effects are not intuitive.


Polar bears are spending more time on land as the sea ice melts, leading to increased contact with grizzly bears. Interbreeding has created hybrids, such as this one shot on Banks Island, N.W.T., in 2006. (Canadian Press)

For example, the loss of ice reduces the fat content of algae that live between layers of ice, making them less nourishing to marine animals, the researchers noted.



The loss of sea ice also has many indirect, inintuitive effects on both marine and land animals.

"It can have pretty dramatic effects on climate even far inland," Brodie said.

That in turn can affect the growth of vegetation on land, disrupting food sources for animals such as caribou.

Indirect effects on migration, breeding

The article notes a number of other potential indirect effects of sea ice loss on land animals:

  • Isolation and increased inbreeding among populations of wolves and arctic foxes, which currently use ice to travel between populations during most of the year.
  • Increased interbreeding and hybridization between grizzly bears and polar bears because polar bears are spending more time on land, where they come into contact with grizzlies.
  • The spread of diseases that were once restricted by sea ice barriers to a certain part of the Arctic, such as phocine distemper virus, which currently affects only eastern Arctic seals.
  • Increased shipping in the Canadian Arctic and the later freeze up of the ice could affect the annual migration of the Dolphin and Union caribou herd.
