William Atkins
Tuesday, 07 April 2009 19:20
Science -
Climate
Page 2 of 3
Two major types of Arctic sea ice exist: younger, thinner, seasonal ice (that melts and re-freezes each year) and older, thicker, winter ice (that remains for two or more years). Some minor types also exist.
It has been relatively easy to measure area of the sea ice cover with satellite images. However, until recently the depth (thickness) of the cover has been difficult at best to measure..
However, scientists at the NASA Jet Propulsion Laboratory (Pasadena, California) produced the first comprehensive map of the thickness of Arctic sea ice using data from the Ice, Cloud, and land Elevation Satellite (ICESat).
The
ICESat (Ice, Cloud,and land Elevation Satellite) mission is part of the NASA Earth Observing System, which measures ice sheet mass balance, cloud and aerosol heights, as well as land topography and vegetation characteristics.
For 2005-2006, the NASA team, lead by Ron Kwok, found that
“… the average winter volume of Arctic sea ice contained enough water to fill Lake Michigan and Lake Superior combined.”
NASA states,
“The older, thicker sea ice is declining and is being replaced with newer, thinner ice that is more vulnerable to summer melt, according to Kwok."
The average thickness of younger, seasonal sea ice is about 6 feet (1.8 meter), while the thickness of older, winter sea ice is about 9 feet (2.7 meters).
According to Charles Fowler and his scientific team at the University of Colorado (UC, Boulder), the thin, seasonal ice has increased from 40 to 50% (of the total Arctic sea ice in winter) in the 1980s and 1990s to about 70% in the 2000s.
Page three concludes.
