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From: Elizabeth Lackey
Date: 10/30/02
Time: 7:40:06 AM
Remote Name: 24.159.72.249
Atmosphere and Ice Shelf Disintegration -
What is the atmosphere?
The atmosphere is a mixture of gases that surrounds teh Earth and any object with a strong gravitational field. The atmosphere consists of the following gases: 78% nitrogen, 21% oxygen, 0.9% argon, and 0.03% carbon dioxide, varying amounts of water-vapor, and trace amounts of hydrogen, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon. The content of water-vapor fluctuates considerably because it depends on the temperature and relative humidity. The atmosphere has existed for around 4.5 billion years. However, since the mid-1800’s, there has been a steady increase in atmospheric dioxide as a result of the burning of fossil fuels, which may affect the Earth’s climate. Comparable concerns are caused by the drastic increase in atmospheric methane. Methane not only adds to the greenhouse effect, but it also reduces the volume of atmospheric hydroxyl ions, which restricts the atmosphere’s ability to cleanse itself of pollutants. The atmosphere has several layers. The troposphere is the lowest layer which extends up to about 16km in tropical regions and about 9.7km in temperate latitudes. Most clouds occur in this layer. The next layer is the stratosphere, which extends from 9-16 km to about 50 km above sea level. The mesosphere layer extends from about 50 km to 90 km above sea level.
“http://encarta.msn.com/encnet/refpages/refarticle.aspx?refid=761559991”
A>E: Intense global warming of more than 0.5 degrees Celsius per decade over the last thirty years has lead to the decline of sea ice. Computer generated models suggest that if greenhouse gases continue to warm the Earth, permanent ice packs will likely melt and will be replaced with seasonal winter ice. (“http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html”)
A>E: Major changes in the Arctic air circulation patterns have also affected sea ice. Over the central Arctic Ocean, average sea level pressure has dropped, and high latitude storms have increased. This has resulted in considerably warm spring and summer air masses over the Arctic Ocean area, which melts some sea ice and pushes the remaining ice away from the shore. (“http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html”)
A>E: A lengthening warm season is also contributing to sea ice decline. When there are open areas of water, called “leads“, darker areas of the ocean reflect less sunlight, therefore, warm up and melt even more ice. (“http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html”)
E>A: Sea ice helps modify the transfer of heat, mass, and momentum between the atmosphere and the ocean. It acts a physical barrier to the exchange of gases, such as carbon dioxide, oxygen and water-vapor. Sea ice behaves as an insulating cover between the cold atmosphere and the considerably warmer ocean. During the winter, the loss of heat to the atmosphere over sea ice is “two orders of magnitude smaller” than loss of heat over open ocean. Sea ice also reflects solar radiation back to space rather than allowing the ocean surface to absorb it. (“http://www.antcrc.utas.edu.au/aspect/seaiceintro.html”)
E>A: Removal of permanent ice packs would significantly increase precipitation in the Arctic Ocean and North Atlantic. Such precipitation, combined with melted sea ice, would result in the reduction of salinity of the ocean water. The North Atlantic Conveyor, which is the main driving force for the Gulf Stream and global ocean circulation, could be severely reduced by these changes in salinity. Furthermore, northern Europe’s climate would be cooled, global marine life would be disrupted, and the ocean would have a reduced ability to remove greenhouse gases from the atmosphere. (“http://archive.greenpeace.org/~climate/arctic99/reports/seaice3.html”)