Why do we study the CRYOSPHERE?
It does seem odd that there is much concern about the cryosphere when most of it is in remote regions. How could something so far away affect anyone? The cryosphere has a number of unique features that cause it to play a large part in the climate system. These features include the high reflectivity of snow and ice and the high insulating capacity of snow and ice which keeps heat in the ocean.
Because of these unique features the polar regions are the most sensitive to climate change and may be the first place we can identify global climate changes.
Measurements over the years 1978-1998 show a decrease in total sea ice area of 615,000 square kilometers or 3% per decade, and a 15% per decade decrease in sea ice thickness. This work indicates that there is less than a 0.1% chance that these decreases in sea ice area and thickness are just an extreme natural variation. Therefore, these studies suggest that a climate change in under way that could affect everyone around the world!
The ice sheets of Antarctica trap a lot of water on the South Pole. There is much concern that if the Earth is warming up, then the West Antarctic Ice Sheet might melt and disintegrate. If this were to happen, the sea level could rise as much as 20m affecting coastal communities worldwide.
During the last ice age, 18,000 years ago, the water taken from the oceans to build up the ice sheets on land in North America and Europe produced a drop in sea level of about 125 m. Therefore, many countries are interested in determining whether Antarctica is currently growing, melting, or is in equilibrium and how it would respond to global climate changes of various types.
The cryosphere is also very reflective compared to most of the other parts of the climate system. It reflects about 50% to 80% of the sunlight that falls on it back to space, as compared to 10% to 30% for water and land. The reflectivity of newly fallen snow ranges even higher, up to 90%. So in the presence of ice generally more than half the solar radiation falling on it is reflected back to space. This represents a loss of energy from the Earth system and can result in colder conditions. These colder conditions can lead to increased ice cover, and thus, a further reduction in the energy absorbed in the Earth system. This is called a positive feedback.
In addition, ice and snow insulate the surface separating it from the atmosphere above. This results in a reduced interaction of the atmosphere with the lithosphere and hydrosphere. Since water is relatively warm in the polar regions, it must remain at or above the freezing point in an area where the air, land, and ice surface temperature can drop as much as 40C below the freezing point, liquid water is a significant energy source for the atmosphere. However, the presence of sea ice cuts off that heat source keeping the atmosphere cold. As sea ice cover changes, there is a dramatic change in the exchange of energy between the atmosphere and the ocean that can ultimately affect weather worldwide.
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