Week Ten: Ice Sheets

Tim Flannery's book, The Weather Makers, discusses results of a core sample analysis from Bonaparte Gulf in Australia.   The sample indicates that about 19,000 years ago in a period of only 100 to 500 years, sea levels rose by an estimated nine to fourteen meters (ten to fifteen yards).   This abrupt rise in water had apparently come from the collapse of an ice sheet in the Northern Hemisphere.   The amount of water released was between one quarter and two Sverdrups poured into the north Atlantic.   (a Severdrup is equal to 1 million cubic meters per second - or about 264 million gallons per second)   In addition to disrupting the Gulf Stream, there had to be profound worldwide consequences of this event.

Picture courtesy of NASA.

One need not go back 19,000 years to be concerned about ice sheet melting.   A 2002 National Geographic article discusses the impact of global warming on ice sheets in Greenland and Antarctica. These regions hold 77 percent of the world's fresh water and if completely melted, would raise sea levels approximately 69 meters (75 yards).

Recent research by NASA Goddard scientists indicates that when the weather is warmer, the Greenland ice sheets are moving faster.   This happens when meltwater pours through large channels until it arrives at the base of the ice sheet. This meltwater serves as a lubricant, allowing the ice sheet to move faster.

The National Snow and Ice Data Center ( NSIDC ) reports that the global sea level is currently rising as a result of ocean thermal expansion and glacier melt, both caused by a rise in global mean temperature.  

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