What is the Cryosphere?

People around the world, including this Inuit man, rely on snow and ice to continue their way of life. Image from CorelDRAW Photos.

Some places on Earth are so cold that water is a solid—ice or snow. Scientists call these frozen places of our planet the "cryosphere." The word "cryosphere" comes from the Greek word for cold, "kryos."

Why does the cryosphere matter?

The cold regions of our planet influence our entire world's climate. Plus, the cryosphere is central to the daily lives of the people, plants, and animals that have made it their home.

Where is the cryosphere?

When scientists talk about the cryosphere, they mean the places where water is in its solid form, where low temperatures freeze water and turn it into ice.

People most often think of the cryosphere as being at the top and bottom of our planet, in the polar regions. We call the area around the North Pole the Arctic and the area around the South Pole the Antarctic. But snow and ice are also found at many other locations on Earth.

Sea ice is one important aspect of both the Arctic region and Antarctica. Image courtesy Andy Mahoney, NSIDC. High-resolution image.

The Arctic

The North Pole is covered by a cold ocean called the Arctic Ocean. In the Arctic Ocean, sea ice grows in the winter and shrinks in the summer.

Frozen ground and permafrost ring the Arctic Ocean. Glaciers, snow, and ice cover the nearby land, including a thick sheet of snow and ice covering Greenland.

Antarctica

Antarctica, at Earth's South Pole, is an icy continent. A huge ice sheet covers the land mass of Antarctica and, in some places, shelves of floating ice extend into the ocean. The outer sections of ice break off or "calve" from these shelves and form icebergs. The icebergs float in the oceans, melting and falling apart as they drift into warmer waters.

The frozen lands of the cryosphere exist beyond the polar regions, in places like Mount Rainier National Park in Washington. © 2008 Jupiter Images. High-resolution image not available.

And in between

The cryosphere also exists in places far away from the cold poles, at high elevations. For example, the snow on Mount Kilimanjaro is in Africa. Frozen soil can be found high in the mountains of the United States, as well as in the northern reaches of Canada, China, and Russia.

The cryosphere expands during the cold winter months. Seasonal areas of the cryosphere include places where snow falls, and where soil, rivers, and lakes freeze.

What is in the cryosphere?

Snow, ice, or both are key ingredients in every aspect of the cryosphere, including sea ice, glaciers, ice shelves, icebergs, and frozen ground.

Snow

Snow is precipitation that falls to the ground as ice crystals. Image from CorelDRAW Photos. High-resolution image not available.

Snow is precipitation made up of ice crystals. When cold temperatures and high humidity levels combine in the atmosphere, snow crystals form. As long as air temperature remains below freezing, the crystals will fall to the Earth as snow. Snow:

1. can be found all over the world, even near the equator at high elevations
2. reflects sunlight and affects our planet's climate
3. provides a habitat for some animals and plants
4. supplies water for people, plants, and animals around the world
5. is an important part of the world's climate

For more details on snow, see All About Snow.

Ice

Ice is the basis for glaciers, sea ice, ice shelves, icebergs, and frozen ground.
Image from Stock.xchng High-resolution image not available.

Ice forms when temperatures drop below the freezing point and liquid water becomes a solid, creating a tightly bonded substance. Ice is a key ingredient in glaciers, sea ice, ice shelves, icebergs, and frozen ground. Naturally occurring ice:

1. exists all over the world, but mostly forms in the high latitudes, at high elevations, or at night when temperatures cool
2. in oceans, lakes, and rivers may not be as common if climate continues to change and temperatures warm
3. provides water for people, animals, and plants
4. on lakes and in oceans can get so thick that special ships called icebreakers have to create a path through the ice
5. can tell scientists about the past climate of Earth through ice cores

For more about the ways that ice shapes Earth's cryosphere, please read below and see All About Sea Ice, All About Glaciers, and All About Snow.

Sea ice

Arctic sea ice influences our entire planet's climate. Image from CorelDRAW Photo. High-resolution image.

Sea ice forms when water in the oceans is cooled to temperatures below freezing. Most sea ice forms in the Arctic and Antarctic Oceans. Sea ice:

1. does not raise sea level when it melts, because it forms from ocean water
2. is closely linked with our planet's climate, so scientists are concerned about its recent decline
3. fills a central role in the lives and customs of native Arctic people
4. provides a place for polar bears, seals, and other animals to live
5. is one way that scientists study the effects of climate change

For general reference information on sea ice, see All About Sea Ice. For analysis of current conditions, see Arctic Sea Ice News & Analysis.

Glaciers

Muir Glacier in Alaska, like many glaciers, has changed through time. At left, the glacier in 1941; at right, the glacier in 2004; from the NSIDC photo pairs collection.

Glaciers are thick masses of ice on land. The ice has built up from many seasons of snowfall. Glaciers move downhill very slowly. Glaciers:

1. cover 10 percent of the world's land
2. are smaller, today, than they used to be because of climate change
3. sometimes look pink because of the algae living in the top layers of the snow and ice
4. store 75 percent of the world's fresh water and provide water for many people around the world
5. change the land they flow through, carving landscapes with their weight

For details on glaciers, see All About Glaciers.

Ice shelves and icebergs

This iceberg was photographed near Antarctica during the NSIDC IceTrek expedition. High-resolution image.

Ice shelves are platforms of ice that form where ice sheets and glaciers move out into the oceans. Ice shelves exist mostly in Antarctica and Greenland, as well as in the Arctic near Canada and Alaska. Icebergs are chunks of ice that break off glaciers and ice shelves and drift in the oceans. Ice shelves and icebergs:

1. raise sea level only when they first leave land and push into the water, but not when they melt in the water
2. break off and melt as temperatures rise; in 2002, Antarctica's huge Larsen B Ice Shelf shattered in only a few months, sending hundreds of icebergs into the ocean
3. provide shelter for krill, small fish that penguins, seals, whales, and sea birds eat
4. are one important area of study for a wide range of scientists who study biology, glaciers, climate, and other fields
5. may hold clues to the future of ice sheets and glaciers in a world with warming temperatures

For more information on ice shelves and icebergs, see Quick Facts on Ice Shelves and Quick Facts on Icebergs. For advanced information, see The State of the Cryosphere: Ice Shelves. For information on the Larsen B breakup, see Larsen Ice Shelf Breakup Events.

Frozen ground

Melting permafrost beneath this building in Dawson, Yukon, is making the building tip. Image from University of Iowa Geoscience Slides Collection High-resolution image.

Frozen ground is soil or rock in which part or all of the water has frozen. If the ground is frozen all year long, we call it "permafrost," or permanently frozen ground. Frozen ground:

1. exists mostly in the Arctic and Antarctic, but frozen ground can also be found at high elevations
2. has begun to melt as climate warms
3. often has an "active layer" near the surface, where plants can live because the soil is thawed for at least part of the year
4. creates problems for people who are building structures, roads, or dams because it can shift them when it melts
5. stores greenhouse gases like carbon and methane; scientists are studying how these gases will affect climate as temperatures warm and permafrost thaws

For more information on permafrost, see All About Frozen Ground. To find out how climate change is affecting frozen ground, see The State of the Cryosphere: Permafrost.