Polar ecosystems are characterized by extreme temperatures, long periods of daylight or darkness, and high levels of biodiversity. However, they are also characterized by a relatively unstable climate, which is subject to rapid changes.

Antarctica is home to the largest ice sheet on Earth, which covers an area of approximately 14 million square kilometers.

Sea ice forms when air temperatures drop below freezing and cause the water in the ocean to freeze.

Grizzly bears are not a type of polar bear. They are a subspecies of brown bear that is found in North America.

Surging is the term for the process by which glaciers move rapidly forward, often over a short period of time.

Overfishing is not a threat to polar ecosystems. It is a threat to marine ecosystems in general, but it does not occur in polar regions.

Calving is the term for the process by which icebergs break off from glaciers.

Puffins are not a type of penguin. They are a type of seabird that is found in the North Atlantic Ocean.

Ablation is the term for the process by which glaciers melt.

Sea lions are not a type of seal. They are a type of pinniped that is found in the Pacific Ocean.

Crevassing is the term for the process by which glaciers form cracks.

Dolphins are not a type of whale. They are a type of cetacean that is found in the oceans around the world.

Surging is the term for the process by which glaciers move slowly forward.

Robins are not a type of polar bird. They are a type of songbird that is found in North America and Europe.

Retreat is the term for the process by which glaciers retreat.