Sea ice | WWF-Canada
© Vicki Sahanatien

Sea ice

The dynamic foundation of Arctic marine life

Vast, vital, with a gleaming blue and white surface reflecting back into space, sea ice is found in polar regions. This frozen ocean water melts, grows and shifts, rich with life and importance. Understanding and conserving the Arctic and all its creatures means understanding sea ice – which covers an average of 25 million square kilometers of the earth, or two-and-a-half times the area of Canada.

Sea ice is the foundation for Arctic marine life, at the base of a complex ecosystem that supports a wide range of species. Light filtering through the ice creates a home for microscopic single-celled algae and zooplankton, which become food for fish like Arctic char and cod, and bowhead whales. Those fish, in turn, sustain seals – the primary prey of polar bears – and beluga whales and narwhals.

Why is sea ice so vital?

Climate control
Sea ice helps keep polar regions – and the whole planet – cool; you might even think of it as “the planet’s air conditioner”. The Earth relies on the Arctic’s white ice and snow to reflect the sun’s warmth back into the atmosphere, creating a cooling effect. As the ice and snow melts, the darker earth, rock and ocean waters actually start absorbing the sun’s heat – which in turn contributes to warming around the globe. This is known as ‘positive feedback’.

Supporting life
Indigenous peoples rely on sea ice for transportation and hunting, while seals, walrus, polar bears, whales and other mammals and sea birds use it for everything from foraging and hunting to birthing. It’s critical as habitat for all life from microscopic algae to massive bowhead whales. Ice has also shaped how species evolution – wildlife have adapted over thousands of years to the Arctic environment and depend on the sea ice for survival.
 / ©: Staffan Widstrand / WWF
Man on skidoo racing across the ice, Baffin Island, Nunavut, Canada, Arctic.
© Staffan Widstrand / WWF

It all comes down to climate change

Scientists are keeping a close eye on Arctic sea ice as the Arctic warms. It’s been shrinking by about 13.4% per decade relative to the 1981 to 2010 average, and the summer of 2012 marked a new record low. Multiyear ice is disappearing, a real concern because it is the only year-round ice habitat and will likely be impossible to replace if the Arctic continues to warm.

Impact on northern communities
These changes to sea ice mean indigenous peoples must adapt hunting strategies and face travelling over thinner and more hazardous ice. Routes used for generations can be unsafe, and patterns of wildlife movement that have long sustained the peoples are becoming increasingly unpredictable.
 / ©: Lee NARRAWAY / WWF-Canada
Sea ice breaking up in Nares Strait, near Ellesmere Island, Nunavut, Canada. © Lee NARRAWAY / WWF-Canada
Impact on wildlife
Wildlife species are losing both their habitat and core of a highly-evolved, balanced food ecosystem. Already it has been observed that the loss of sea ice in the southern Arctic has affected wildlife species’ habitat. For example, the loss of sea ice is pushing polar bears into communities, putting bear and human lives at risk. At the same time, walruses are no longer able to haul-out on sea ice, and caribou are at greater risk of falling through thin ice as they cross between islands. The loss of sea ice also opens up the Arctic ocean to new species. The killer whale, for example, was once a rare sight in the Canadian Arctic, but is now commonly observed.
 / Steve Morello / WWF-Canon
Polar bear (Ursus maritimus) walking on ice floes. Spitsbergen, Svalbard, Norway. © Steve Morello / WWF-Canon
Impact on industrial development
The loss of sea ice creates more opportunity for development. This can include everything from increased shipping to oil and gas development. With these opportunities come potential new risks in the form of noise and spills or accidents.

Learn about WWF’s work in supporting shipping best practices

Where will the sea ice stay?

In order to understand the future of sea ice in the face of climate change, scientists are creating models to explore what the ice might look like in years to come. As part of the Last Ice Area project, WWF commissioned research on Arctic sea ice conditions in the Arctic Archipelago. This closer look will help us understand what will happen at a more region al scale, since most research is conducted at a global or circumpolar scale. The results showed sea ice loss varies across the Arctic, but the trend from both traditional knowledge and scientific modeling confirm progressive and accelerating loss of sea ice. The models also used the best science available to show where sea ice will be most resilient – in the Last Ice Area.
©: Andrew S. Wright / WWF-Canada
Remnants of sea ice in late summer, Resolute Bay, Nunavut, Canada
© Andrew S. Wright / WWF-Canada

© Vicki Sahanatien
© Vicki Sahanatien

Sea ice: a bear necessity

Polar bears have evolved to live on the frozen surface of the ocean. They spend most of the year on the ice, where they are able to hunt ringed seals – which pup and molt on the ice – and other prey that sustain them. In the summer, some bears move onto land where they live off stored body fat, and wait for their chance to head back onto the ice when it reforms. Today, melting sea ice means that many polar bears are spending more and more days on land each year.

Read more about polar bears.
© Andrew S. Wright / WWF-Canada
Gulls perch on the last of the melting summer ice, at Pond Inlet, Nunavut, Canada
© Andrew S. Wright / WWF-Canada

The Last Ice Area

As sea ice retreats due to climate change, scientific models have identified an area where sea ice is expected to last the longest. This is called the Last Ice Area, which will provide critical future habitat for species that need the ice.

See how WWF is planning for the future.


© (C)WWF
See how sea ice, species habitat, shipping, and other human activities overlap in the Arctic by exploring the WWF map.

Types of Sea Ice

First-Year or Annual Ice - ice with a maximum growth of one year, developing from young ice. This type of ice must be ‘re-colonized’ by algae and bacteria after each summer melt season, which affects the range of algae that it can host. It’s rubbery and flexible because of its salt content.

© Vicki Sahanatien
Multi-year Ice - ice that has lasted through at least one summer melt season. It has more air pockets and less brine than first-year ice and can provide fresh drinking water. It is critical habitat from many species that live on or under the ice year-round. It tends to be brittle.

© Vicki Sahanatien
Fast Ice - ice that’s connected to the shore or ocean bottom. It doesn’t move with the currents or winds, and provides a home for ringed seals when building their lairs.

Oil Spills in the Arctic

© Dan Slavik / WWF-Canada
Explore the risk of oil spills in the Beaufort Sea at

Important Sea Ice Features

Sea Ice Minimum Extent – when the sea ice covers the smallest area in the Arctic, typically in September.

Sea Ice Maximum Extent  when the sea ice covers the largest area of the Arctic.

Polynyas  areas of year-round open water in the sea ice, often created by winds, tides, currents and upwellings. They’re important wildlife habitat, acting as breathing holes and foraging spots. Many of Canada’s best known sea bird colonies are by polynyas. Many archaeological sites are located near polynyas.

Floe Edge – where the land-fast ice stops and the open water or moving ice starts. The floe edge often attracts polar bears and people for hunting, as well as prime habitat for sea birds. It’s often considered to be a highly productive area.

© Vicki Sahanatien