|MadSci Network: Earth Sciences|
The air is Antarctica is considered "dry" because all of the moisture has already precipitated out due to the cold temperature. In addition, cold air simply cannot hold much water (look up the Goff-Gratch equation for water vapor partial pressures over water and ice for more). A change in the global sea levels takes place when there is a net displacement of water between the continents and the oceans. If the temperature over Antarctica rises significantly, the air may hold more water vapor. However, this will not lead to an overall increase in precipitation. The reason is because most of the moisture that feeds precipitation over the Antarctic continent comes from the circulation of moist air from the tropical regions. Whereas moist air entering a "cold" Antarctica is more-or-less immediately precipitated as snow onto the continent - moist air entering a "warmer" Antarctica will not be precipitated as much. In addition, an increase in temperature will cause existing ice sheets in Antarctica to melt and break away. Recall in 2002 when the "Larsen B" ice shelf (about the size of Rhode Island) shattered and broke away into the ocean. An event like this is HUGE since it took tens of thousands of years for those ice sheets to form. This was a net loss of water from the continents and it resulted in a rise in the global sea level. - In Koo
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