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Cryosphere

The cryosphere plays an essential role in regulating the Earth's climate. But what is the meaning of the cryosphere? No, the cryosphere is not some alternate dimension: it's ice! We will be exploring cryosphere characteristics and examples, its role in the water cycle, and how the cryosphere is being altered due to climate change. Feeling chilly yet? You might want to grab a jacket...

Cryosphere meaning and definition

Cryosphere, cryosphere diagram, StudySmarterFig. 1 - The cryosphere is all of the earth's frozen water combined

The cryosphere is the total of all water on the Earth's surface that is currently frozen. Essentially, it's the combination of all of the ice on the planet.

The name 'cryosphere' comes from the combination of the Greek words 'krios' or 'kryos' for cold, and 'sphaira' for globe/sphere, with the latter referring to the Earth. The majority of the cryosphere is located close to the poles (the Arctic and Antarctica) in the form of ice sheets, shelf ice, and frozen ground. However, frozen water can easily be found outside of polar regions in the form of snow and glaciers, though this amount is minor compared to the volume of ice in the Arctic and Antarctica.

Cryosphere examples and characteristics

Some of the terms used to describe the different components of the cryosphere can be confusing at first. For example, how are ice shelves different from ice sheets? But don't worry: we'll break it down.

Glacier

A glacier is a slow-moving mass of freshwater ice that often forms on mountain slopes. They accumulate rock and sediment as they travel down-slope eroding the rock beneath them. Glaciers grow during the winter as snow builds up and compacts into ice, and then retreat (shrink) in the summer as sections of them melt as temperatures rise. Glaciers can easily be found outside polar regions like the widely studied glacier Mer de Glace on the Mont Blanc (a mountain in the French Alps).

Snow

Snow is an important part of the cryosphere as it is the most volatile part of the cryosphere. Out of all the components of the cryosphere, snow covers the second-largest amount of the Earth. Across the span of a year, the volume and areal coverage of snow vary greatly with new snowpacks on mountains forming or expanding in the winter and subsequently melting away or shrinking over the rest of the year. These snowpacks often form the source of rivers that rely on the snowmelt.

Frozen ground

When temperatures drop below 0°C for prolonged periods, the water content within the soil will freeze making the ground hard and compacted. Frozen ground is differentiated from simple frost on the ground as frozen ground involves the water in the soil freezing at least several centimetres down, rather than just the surface. Frozen ground covers the largest surface area out of the whole of the cryosphere. Permafrost is frozen ground that is composed of frozen decaying organic matter. This is the cryosphere carbon store which is important in regulating the climate.

Permafrost is any ground that is completely frozen, i.e. 0°C (32°F) or colder, for a minimum of 2 continuous years.

Ice sheets

An ice sheet is a glacial mass that is found on land and is larger than 50,000 km2 (19,000 mi2). Ice sheets hold about 99% of all the Earth's freshwater. Currently, only two ice sheets exist on Earth, namely Antarctica and Greenland. The Antarctic ice sheet is much larger than the Greenland ice sheet. During the Last Glacial Maximum, between 31,000 and 16,000 years ago (when the Earth’s ice coverage was at its largest), large ice sheets covered the entirety of Northern Europe, Canada, and Patagonia.

Cryosphere, Glacial striations still visible, StudySmarterFig. 2 - Glacial striations visible in the rock at New York's Central Park, G. Scott Segler/ Wikimedia Commons, CC-BY-SA-4.0

Ice caps

An ice cap is a large mass of ice that is smaller than 50,000 km2. They are a lot more common than ice sheets, and many can be found across the Earth. These are different from polar ice caps, which are not true ice caps, as they are either larger than 50,000 km2, as in the case of the Antarctic polar ice caps, or they are a combination of an ice sheet and sea ice, as in the case of the Arctic polar ice caps.

Ice shelves

An ice shelf is a section of an ice sheet or a glacier that has flowed down towards the coast and then into the ocean, where it will then float on top. These are mostly found around the Antarctic, northern Europe, and northern America.

Ice shelves and icebergs are important in the study of climate change and global warming, as they can offer insight into glacial melting.

Sea ice

Sea ice, much like it sounds, is seawater that has frozen over the surface of the ocean. Sea ice floats on seawater because it is less dense than seawater. Sea ice can cover up to 12% of the Earth’s oceans at any given time, but this value changes over the course of a year since sea ice typically forms in the winter and melts in the summer.

Sea ice is very important as it keeps the polar regions cool. This occurs due to the albedo effect, or, a surface's ability to reflect incoming solar energy. White sea ice is very bright, and thus reflects about 80% of incoming sunlight. On the other hand, when sea ice melts, there is less surface to reflect the sunlight, so the ocean absorbs it. A lack of sea ice, therefore, heats the oceans and causes Arctic temperatures to rise.

Lake ice and river ice

Frozen lakes and rivers are the smallest parts of the cryosphere and are often discussed more for their impact on local geography than their contribution to the cryosphere. They have a negligible impact on the cryosphere at large.

How large is the cryosphere?

The true size of the cryosphere is very hard to estimate due to how much it can shrink/expand throughout the year due to seasonal temperatures. For example, there is significantly less Arctic sea ice at the end of summer than there is during winter.

Cryosphere Cryosphere, Volume difference, StudySmarterFig. 3 - Cryosphere volume difference, NASA Earth Observatory, Public Domain

This doesn’t mean it is impossible to estimate the volume of water that is in the cryosphere. Around 70% of the Earth’s freshwater is thought to be locked up in glaciers and other bodies of ice, making it the largest store of freshwater. In addition, 10% of the land on the surface of the Earth is made up of the cryosphere, either as ice sheets, glaciers, or frozen ground. Additionally, as we've already mentioned, up to 12% of the Earth’s ocean surface is frozen as sea ice.

The cryosphere impact factor

There are two major ways that the cryosphere influences the climate of our planet. The first effect of the cryosphere is the increase in albedo, a surface's ability to reflect incoming solar energy. The vast bodies of ice at the poles are very effective at reflecting incoming solar energy into space, which reduces the warming effect of the sun upon the Earth. Normal ocean water reflects around 6% of incoming solar radiation, whereas sea ice reflects around 50%.

Climate change may significantly change this. As the ice caps melt with rising temperatures, it will allow even more solar energy to be absorbed into the oceans, warming the Earth further in a feedback loop.

Cryosphere, Changes in albedo produced by the cryosphere, StudySmarterFig. 4 - Changes in albedo produced by the cryosphere

The above image illustrates the contrast in albedo between ocean surfaces that do have ice and those that do not. On the ocean open, as much as 94% of solar energy is absorbed directly into the ocean, with only 6% being reflected back. Compare this to an ocean surface covered with ice and snow: as much as 90% of the solar energy is being reflected, keeping the ocean below cool.

The other way that the cryosphere impacts the global climate is through the mass storage of carbon in permafrost. Most permafrost is found within the Arctic Circle of the Northern Hemisphere, with large stretches of it in Canada and Russia, but it can be found globally with some even being discovered under the ice sheets of Antarctica. A lot of the permafrost formed during the Pleistocene (2.6 million to 11,700 years ago) which is why the remains of mammoths and woolly rhinos can often be found within it.

In terms of impacting the climate, the decaying vegetation that has been frozen in the permafrost is a large store of carbon itself, but there are also many large air pockets of carbon dioxide and methane trapped within the permafrost, which are a much larger store of carbon. There are approximately 1,400 gigatons of carbon stored in the Earth's permafrost, compared to the 850 gigatons of carbon in the Earth's atmosphere. 1

A gigaton = one billion tons!

Much like the albedo effect, the warming of the Earth has the potential to create a positive feedback loop. As the permafrost melts, it releases the trapped methane and carbon dioxide which creates more warming, which then leads to more permafrost melting in a continuous cycle.

The future of the cryosphere

The encroachment of climate change with rising temperatures poses a great threat to the cryosphere. Further ice sheet retreats in the Antarctic and Greenland will increase global sea levels as water from the melted ice will flow into the oceans.

It is important to note that sea ice melting will not increase sea levels as the sea ice already displaces the same volume of water, much like how ice cubes melting in a glass of water will not cause the volume of water to increase. Similarly, the formation of sea ice does not decrease sea levels even though ice expands when it freezes. This is because the volume change caused by freezing and expansion of water is instead forced above the ocean surface. This is why sea ice and icebergs only have a small amount of their volume above the water with the majority submerged.

The same cannot be said for land ice. When land ice or glaciers melt the volume is released into the ocean. This melting of land ice, which raises sea levels, alongside the positive feedback loops mentioned previously, means that the threats to the cryosphere can very easily translate into threats for us.

Cryosphere - Key takeaways

  • The cryosphere includes all water on the Earth that is frozen.
  • There are many components of the cryosphere that vary greatly in size.
  • The size of the cryosphere can be hard to estimate due to how much it changes annually.
  • Around 70% of the Earth’s freshwater composes of the cryosphere, which doesn’t include frozen ground or sea ice
  • Crucially, the cryosphere plays a significant role in regulating the climate, especially due to the albedo effect.
  • Climate Change may drastically affect the cryosphere which in turn will greatly affect our species.

__________________________________________________________________

Sources:

NASA: https://earthobservatory.nasa.gov/images/149613/arctic-sea-ice-is-more-modest-than-maximal

Albedo image: https://nsidc.org/cryosphere/seaice/processes/albedo.html

References

  1. Kevin Schaffer. Methane and Frozen Ground. National Snow & Ice Data Center. https://nsidc.org/cryosphere/frozenground/methane.html#:~:text=There%20is%20a%20huge%20amount,of%20carbon%20frozen%20in%20permafrost.

Frequently Asked Questions about Cryosphere

The cryosphere is the total of all water on Earth that is in the form of ice.

The majority of the cryosphere is located within polar regions (the Arctic and Antarctic), but other minor parts like glaciers and snow can be found in temperate regions and sometimes even in the tropics like the snow on Mt Kilimanjaro in Kenya. 

There are divisions in the cryosphere for the different components these are glaciers, snow, frozen ground, ice sheets, sea ice, ice shelves, and lake/river ice.

Permafrost is not “a” cryosphere but instead is part of the global cryosphere. There is only one cryosphere on earth. 

The cryosphere is important because it helps to regulate the climate by storing carbon in the form of permafrost and increasing the albedo (reflectivity) of the Earth so less solar energy remains to heat the earth. In addition, many rivers’ sources are snowpacks or large glaciers that melt during the summer so without them those rivers would have no source during the summer. 

Final Cryosphere Quiz

Question

What does the Cryosphere mean? 

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Answer

The Cryosphere is the total of all water on Earth in the form of ice or similarly frozen.

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How does the Cryosphere help to regulate the Earth’s Climate?

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Answer

Through increasing the Earth’s Albedo (reflectivity) and storing massive amounts of carbon in permafrost.

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Where is the Cryosphere located?


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Answer

The Cryosphere is mostly composed of the frozen water at the poles of the Earth, but ice and snow can be found worldwide but is more so dependent on the season.

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Why might it be difficult to estimate the true size of the Cryosphere?


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Answer

The Cryosphere changes in size and makeup throughout the year as snowpacks, glaciers and ice sheets expand during the winter, then proceed to shrink during the summer.

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How can the Cryosphere be important to river processes?


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Answer

From late spring to late Autumn snowpacks and glaciers can be the primary source for many rivers. 

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How do ice shelves form?


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Ice shelves form when sections of ice sheets or glaciers flow into the ocean creating a floating platform of freshwater ice. 

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What is the difference between an ice cap and an ice sheet?


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An ice cap is a large mass of ice on land <50,000km2 whereas ice sheets are larger than 50,000km2.

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How might the Cryosphere decreasing in size due to warming temperatures affect the planet?


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Answer

As the ice sheets, ice caps, and glaciers melt and flow into the ocean, the sea level will rise. The melting of the cryosphere will also reduce albedo and cause the permafrost to release all the captured methane and carbon dioxide furthering the warming effect.

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Does the formation and melting of sea ice have any impact on sea level? Explain why.

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Answer

No, because whilst water expands as it freezes, the volume increase caused by this expansion is forced above the ocean’s surface. 

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Question

What does the Last Glacial Maximum refer to?

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Answer

A period of time between 31,000 - 16,000 years ago where the glacial extent of the earth was at its largest.

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Question

How much of the Earth’s freshwater is thought to be part of the Cryosphere?
30%

50%
70%
90%

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Answer

70%

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Why does lake ice and river ice get often overlooked in terms of the Cryosphere?

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Answer

Lake ice and river ice form an incredibly small part of the Cryosphere and have negligible impact on the Cryosphere at large.

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Are the polar ice caps true ice caps?


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No, as they both are larger than the 50,000km2 maximum for them to be classed as ice caps.

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Where are the two ice sheets located?


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Antarctica and Greenland.

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How much of the Earth’s land surface is part of the Cryosphere?


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Answer

10%

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60%

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