Global Warming and Land Ice
Over the past century, sea level has slowly been rising. This is in part due to the addition of water to the oceans through either the melting of or the "calving" off of icebergs from the world's land ice. Many individual mountain glaciers and ice caps are known to have been retreating, contributing to the rising sea levels. It is uncertain, however, whether the world's two major ice sheets-Greenland and Antarctica-have been growing or diminishing. This is of particular importance because of the huge size of these ice sheets, with their great potential for changing sea level. Together, Greenland and Antarctica contain about 75% of the world's fresh water, enough to raise sea level by over 75 meters, if all the ice were returned to the oceans. Measurements of ice elevations are now being made by satellite radar altimeters for a portion of the polar ice sheets, and in the future they will be made by a laser altimeter as part of NASA's Earth Observing System (EOS). The laser altimeter will provide more accurate measurements over a wider area.
The Greenland ice sheet is warmer than the Antarctic ice sheet and as a result, global warming could produce serious melting on Greenland while having less effect in the Antarctic. In the Antarctic, temperatures are far enough below freezing that even with some global warming, temperatures could remain sufficiently cold to prevent extensive surface melting.
Where ice sheets extend outward to the ocean, the ice tends to move out over the surrounding water, forming "ice shelves." There is concern that, with global warming, the water under the ice shelves would be warmer and cause them to break up more readily, forming very large icebergs. If the ice shelves of West Antarctica were to break up, this would release more inland ice in an irreversible process, possibly leading to sea level rises of several meters.
In addition to increasing the amount of melting, global warming would also be expected to increase the amount of precipitation in the polar regions. There are three reasons for this: 1) warmer air can carry more moisture than colder air; 2) warmer wates would encourage increased evaporation from the ocean; and 3) lessened sea ice would also lead to more evaporation from the ocean, as more ocean area would be exposed directly to the atmosphere. Global warming could therefore be expected initially to increase both melting and snowfall. Depending on which increase dominates, the early result could be either an overall decay or an overall growth of the ice sheets.
Global Warming and Land Ice
Over the past century, sea level has slowly been rising. This is in part due to the addition of water to the oceans through either the melting of or the "calving" off of icebergs from the world's land ice. Many individual mountain glaciers and ice caps are known to have been retreating, contributing to the rising sea levels. It is uncertain, however, whether the world's two major ice sheets-Greenland and Antarctica-have been growing or diminishing. This is of particular importance because of the huge size of these ice sheets, with their great potential for changing sea level. Together, Greenland and Antarctica contain about 75% of the world's fresh water, enough to raise sea level by over 75 meters, if all the ice were returned to the oceans. Measurements of ice elevations are now being made by satellite radar altimeters for a portion of the polar ice sheets, and in the future they will be made by a laser altimeter as part of NASA's Earth Observing System (EOS). The laser altimeter will provide more accurate measurements over a wider area.
The Greenland ice sheet is warmer than the Antarctic ice sheet and as a result, global warming could produce serious melting on Greenland while having less effect in the Antarctic. In the Antarctic, temperatures are far enough below freezing that even with some global warming, temperatures could remain sufficiently cold to prevent extensive surface melting.
Where ice sheets extend outward to the ocean, the ice tends to move out over the surrounding water, forming "ice shelves." There is concern that, with global warming, the water under the ice shelves would be warmer and cause them to break up more readily, forming very large icebergs. If the ice shelves of West Antarctica were to break up, this would release more inland ice in an irreversible process, possibly leading to sea level rises of several meters.
In addition to increasing the amount of melting, global warming would also be expected to increase the amount of precipitation in the polar regions. There are three reasons for this: 1) warmer air can carry more moisture than colder air; 2) warmer wates would encourage increased evaporation from the ocean; and 3) lessened sea ice would also lead to more evaporation from the ocean, as more ocean area would be exposed directly to the atmosphere. Global warming could therefore be expected initially to increase both melting and snowfall. Depending on which increase dominates, the early result could be either an overall decay or an overall growth of the ice sheets.
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Global Warming and Land Ice
Over the past century, sea level has slowly been rising. This is in part due to the addition of water to the oceans through either the melting of or the "calving" off of icebergs from the world's land ice. Many individual mountain glaciers and ice caps are known to have been retreating, contributing to the rising sea levels. It is uncertain, however, whether the world's two major ice sheets-Greenland and Antarctica-have been growing or diminishing. This is of particular importance because of the huge size of these ice sheets, with their great potential for changing sea level. Together, Greenland and Antarctica contain about 75% of the world's fresh water, enough to raise sea level by over 75 meters, if all the ice were returned to the oceans. Measurements of ice elevations are now being made by satellite radar altimeters for a portion of the polar ice sheets, and in the future they will be made by a laser altimeter as part of NASA's Earth Observing System (EOS). The laser altimeter will provide more accurate measurements over a wider area.
The Greenland ice sheet is warmer than the Antarctic ice sheet and as a result, global warming could produce serious melting on Greenland while having less effect in the Antarctic. In the Antarctic, temperatures are far enough below freezing that even with some global warming, temperatures could remain sufficiently cold to prevent extensive surface melting.
Where ice sheets extend outward to the ocean, the ice tends to move out over the surrounding water, forming "ice shelves." There is concern that, with global warming, the water under the ice shelves would be warmer and cause them to break up more readily, forming very large icebergs. If the ice shelves of West Antarctica were to break up, this would release more inland ice in an irreversible process, possibly leading to sea level rises of several meters.
In addition to increasing the amount of melting, global warming would also be expected to increase the amount of precipitation in the polar regions. There are three reasons for this: 1) warmer air can carry more moisture than colder air; 2) warmer wates would encourage increased evaporation from the ocean; and 3) lessened sea ice would also lead to more evaporation from the ocean, as more ocean area would be exposed directly to the atmosphere. Global warming could therefore be expected initially to increase both melting and snowfall. Depending on which increase dominates, the early result could be either an overall decay or an overall growth of the ice sheets.
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