Arctic Ocean

Sea ice is white and shiny.

It bounces sunlight back into the sky. That helps keep the Arctic cold.

Sea ice is much brighter than the dark ocean. The open ocean reflects only about 6 percent of the Sun's energy and soaks up the rest, but sea ice reflects 50 to 70 percent, and snow-covered sea ice up to 90 percent.

When sea ice melts in summer, more dark water is uncovered. The water soaks up more of the Sun's heat, which warms things further and melts more ice. That is why the poles are especially sensitive to climate change.

Sea ice helps keep the polar regions cool and moderates global climate through its albedo: NSIDC gives about 6% reflection for open ocean, 50–70% for bare sea ice and up to 90% for snow-covered sea ice, which insulates the ice and delays summer melt.

As summer melt exposes dark water, absorption rises, warming the surface and surroundings further, so a small warming at the poles leads to greater warming over time. NSIDC reports a dramatic decline in both the thickness and extent of Arctic summer sea ice since the 1980s, consistent with a warming Arctic, and notes that Arctic sea ice is more significant than Antarctic sea ice for understanding global climate, because much more of it remains through the summer.

Scientists use satellites to watch the sea ice every day.

In summer the ice gets smaller. In winter it grows again.

Scientists at the National Snow and Ice Data Center track the Arctic's sea ice from satellites every day. The ice usually grows to its biggest in March and shrinks to its smallest in September.

In 2026 the summer was cool and stormy over the Arctic Ocean. The smallest extent of the year tied for tenth lowest since satellite records began, and the ice then started freezing again quickly.

NSIDC updates sea ice extent daily with a one-day lag, using a 15% concentration threshold to mark the ice edge because it agrees best between satellite and ground observations; extent and area are different measures, and NSIDC reports mainly extent. The annual maximum and minimum usually occur in March and September.

NSIDC's analysis for 2026 describes a cool, stormy summer over the Arctic Ocean despite record or near-record global air temperatures in June to August; the minimum extent tied for tenth lowest in the satellite record with 2008, 2010 and 2025, with a loose pack on the Atlantic side reaching the pole, followed by a rapid freeze-up.

Seals and walruses rest on the ice and have their babies there.

Polar bears hunt on the ice. Tiny plants called algae grow on the ice too.

Sea ice is a home for Arctic animals. Seals and walruses rest and give birth on it, and polar bears use it to hunt and breed. Arctic foxes, whales and caribou find food there too.

The food web starts small. Algae grow on the sea ice, and when the ice melts in spring, they help start a bloom of tiny floating plants called phytoplankton. Fish eat them, and bigger animals eat the fish. People living near the sea ice also depend on it for hunting and for their way of life.

NSIDC describes sea ice as a resting and birthing place for seals and walrus, a hunting and breeding ground for polar bears and a foraging ground for arctic foxes, whales, caribou and other mammals; poor ice conditions stress marine mammals.

Life thrives above, below and within the ice. Algae grow on it, and when the ice melts in spring they enter the water and fuel a phytoplankton bloom, the foundation of the marine food chain that sustains fish, migratory birds and other species. Communities living near sea ice depend on it for subsistence and cultural identity; how the ice forms, how thick it is and where it opens decide where animals are and whether it is safe to hunt.

Visitors to the Arctic stay with their group.

If you see a polar bear, tell the guide and never go near it. Leave flowers, stones and bones where they are.

On Arctic expedition cruises, the Association of Arctic Expedition Cruise Operators asks guests to always follow their guide and never wander away from the group.

Polar bears can be met anywhere in bear areas. If you spot one, stay calm, tell your guide at once and never approach it. Keep quiet near animals and nesting birds, don't pick flowers, and leave stones, bones and driftwood where you find them.

AECO's visitor guidelines ask guests to leave no lasting signs (no litter, engravings, cairns or rearranged stones), to avoid trampling plants or making paths, not to pick flowers, and to leave stones, bones, antlers and driftwood in place. Cultural remains are protected by law with a 100 m protected zone around them, and all fauna is treated as protected, with quiet behavior near animals and nesting birds and minimum distances set by the leaders.

Its number one safety rule is to follow the expedition leader's instructions and never stray from the group. In polar bear areas bears may appear at any time; guests who spot one should stay calm, inform the guide immediately, never approach, and never leave food out.