Monday, July 21, 2008
1.Polar ice cap
(Reference:-Wikipedia,the free encyclopedia.)
A polar ice cap is a high-latitude region of a planet or moon that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of solid phase matter in the polar region. This causes the term 'polar ice cap' to be somewhat of a misnomer, as the term ice cap itself is applied with greater scrutiny as such bodies must be found over land, and possess a surface area of less than 50,000 km²: larger bodies are referred to as ice sheets.
The composition of the ice will vary. For example Earth's polar ice caps are mainly water ice, while Mars's polar ice caps are a mixture of solid phase carbon dioxide and water ice.
Polar ice caps form because high-latitude regions receive less energy in the form of solar radiation from the sun than equatorial regions, resulting in lower surface temperatures.
The polar ice caps have changed dramatically over the last 20 years. According to prevalent scientific theory, this change can be attributed to global warming resulting from climate change caused largely by the burning of fossil fuels. Seasonal variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to climate variation. See ice age, polar climate.
2.Impacts of global warming on polar ice caps
This is a very important statement to think about how Global warming may have significant impacts on our environment over the next century. Many say that it is currently responsible for changes in weather and climate patterns already. The short-term variability of the weather makes it very hard to base decisions on only a few years’ observations, but the long-term trends (measurements over a hundred years) do indicate that we are on a warming trend.
EARTH POLAR ICE CAPS
Earth's north pole is covered by floating pack ice (sea ice) over the Arctic Ocean, the Arctic ice pack. Portions of the ice that don't melt seasonally can get very thick, up to 3–4 meters thick over large areas, with ridges up to 20 meters thick. One-year ice is usually about a meter thick. The area covered by sea ice ranges between 9 and 12 million km². In addition, the Greenland ice sheet covers about 1.71 million km² and contains about 2.6 million km³ of ice.
While the International Panel on Climate Change 2001 report predicted that the North polar ice cap would last to 2100 in spite of global warming caused by climate change, the dramatic reduction in the size of the ice cap during the northern summer of 2007 has led some scientists to estimate that there will be no ice at the North Pole by 2030 with devastating effects on the environment.
Other scientists such as Wieslaw Maslowski, a professor at the Naval Postgraduate School, estimate that there will be no summer ice by as soon as 2013. He argues that this projection is already too conservative as his dataset did not include the minima of 2005 and 2007.
Due to the Global warming(climate change)northern polar ice cap is being melted far beyond than the south pole.Melting of north polar ice cap is so rapid.
The land mass of the Earth's south pole, in Antarctica, is covered by the Antarctic ice sheet. It covers an area of almost 14 million km² and contains 25-30 million km³ of ice. Around 70% of the fresh water on the Earth is held in this ice sheet. In addition, the West Antarctic Ice Sheet covers 3.2 million km² and the Ross Ice Shelf covers 0.5 million km². See Climate of Antarctica.
Global warming has increased the volume of summer meltwater on glaciers, which has weakened ice shelves. The dramatic collapses of The Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, and the Jones Ice Shelf show the impacts of climate change on the Antarctic ice cap.
EFFECT OF POLAR ICE CAP MELTATION ON RISE OF OCEAN
You may have heard about global warming. It seems that in the last 100 years the earth's temperature has increased about half a degree Celsius. This may not sound like much, but even half a degree can have an effect on our planet. According to the U.S.
Environmental Protection Agency (EPA) the sea level has risen 6 to 8 inches (15 to 20 cm) in the last 100 years.
MARS POLAR ICE CAP
The planet Mars also has polar ice caps, but they consist of frozen
carbon dioxide as well as water. The ice caps change with the Martian seasons-the carbon dioxide ice sublimes in summer, uncovering a surface of layered rocks, and then reforms in winter. These polar ice caps are one of the main reasons that people believe that life exists on Mars.
Global warming on Mars?
In the other study, led by Michael C. Malin, features at the south pole were observed to retreat by up to 10 feet (3 meters) from one Martian year to the next.
The odd shapes -- circular pits, ridges and mounds -- were first photographed in 1999. Since then, the features have eroded away by up to 50 percent.
The pits are growing, the ridges between them shrinking.
Caplinger and Malin caution that a year's worth of data does not reveal when this erosion began or how long it will continue. Yet they speculate that the features could have been created in a Mars' decade and may erode away completely within one to two decades.
"We know that the pits we see at the surface today are not very old, and that they will not last very long," Malin said.
Water or not on mars?
The rate of erosion suggests the features are made of moderately dense but solid carbon dioxide, rather than water ice, the scientists conclude. But that does not preclude the possibility of water ice at the south pole.
"We don't know what's underneath," Caplinger said. "You could certainly have water ice under carbon dioxide."
He said the only way to find out is to go there and drill down.
The newly observed melting, if it is part of a trend, could pump enough carbon dioxide in the atmosphere of Mars to increase its mass by 1 percent per decade, the scientists said. Already, the atmosphere of Mars is roughly 95 percent carbon dioxide.
Caplinger said no one knows for sure what effect the extra carbon dioxide might have on the climate. "Not much," he figures.
But he said many scientists assume that Mars undergoes climate change. Photos of the surface suggest water may once have flowed on Mars, implying that it would have been warmer. And Earth's ice ages offer the lesson that change is inherent in a climate
Posted by Edward at 1:43 AM