|  | | | | | | | Land and sea ice in the Arctic | |
CryoSat -2 - science overview
Almost 80% of the Earth's fresh water is locked up in the cryosphere, i.e. snow, ice and permafrost. The cryosphere plays an important role in moderating the global climate – and as such, the consequences of receding ice cover due to global warming are far reaching and complex.
Due to its high albedo, ice masses directly affect the global energy budget by reflecting about 80% of incident sunlight back out to space. Thus, once formed, ice tends to be maintained. However, if ice cover were to decrease, less solar radiation would be reflected away from the surface of the Earth – causing the ice to absorb more heat adn consequently melt faster still.
Around the North Pole, an area of sea ice the size of Europe melts away every summer and then freezes again during the winter. The thickness of Arctic sea ice plays a central role in polar climate as it moderates heat exchange by insulating the ocean from the cold polar atmosphere.
A decrease in sea ice could disturb ocean circulation in patterns in the North Atlantic
As sea ice forms, the salinity and therefore the density of the upper ocean increase. The density increase causes the surface waters to sink – in essence acting as a pump, driving cold, deep ocean currents from the polar regions towards the Equator. A reduction in Arctic sea ice could significantly disrupt the Gulf Stream which transports warm surface waters northwards from the Gulf of Mexico to the sub-polar waters east of Greenland. It is thanks to the Gulf Stream that north-west Europe currently enjoys annual temperatures of about 9° C higher than average for the latitude.
As well as influencing how much sunlight is reflected back to space, continental ice has an impact on sea level. The large ice sheets covering Antarctica and Greenland amount to about 28 million km3, which means that sea level is about 65 m lower than it would be if these ice sheets didn't exist. Whilst evidence suggests that these ice sheets are relatively stable, there are indications that rapid changes are occurring around their margins.
| | CryoSat | |
CryoSat-2's icy mission is dedicated to monitoring very precise changes in the elevation and thickness of polar ice sheets and floating sea ice over a 3-year period. The observations that CryoSat-2 makes will determine whether or not our ice masses are thinning due to global warming.
Last update: 2 May 2006 | |
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CryoSat: ESA'S ice mission