Global warming raises the specter of melting glaciers and ice sheets at both ends of the globe. The West Antarctic Ice Sheet extends over both land and water west of Antarctica's Transantarctic mountains. Even partial melting of this vast ice sheet would cause a significant rise in sea level. But where...and how much?
The Science
The Intergovernmental Panel on Climate Change has estimated that a collapse of this ice sheet would raise sea levels around the world by about 16.5 feet, on average, and that figure is still widely used. However, that theoretical average does not consider several key forces, such as gravity, changes in the Earth's rotation or a rebound of the land on which the massive glacier now rests, scientists say in the new study.Aside from incorporating the gravitational effect, the new study adds further wrinkles to the calculation - the weight of the ice forcing down the land mass on which it sits, and also affecting the orientation of the Earth's spin. When the ice is removed, it appears the underlying land would rebound, and the Earth's axis of rotation defined by the North and South Pole would actually shift about one-third of a mile, also affecting the sea level at various points.
A significant part of the concern is that much of the base of this huge ice mass actually sits below sea level, forced down to the bedrock by the sheer weight of the ice above it. Its edges flow out into floating ice shelves, including the huge Ross Ice Shelf and Ronne Ice Shelf. This topography makes it "inherently unstable," Clark said.
The Risk Management Data
When these forces are all taken into calculation, the sea level anywhere near Antarctica would actually fall, the report concludes, while many other areas, mostly in the Northern Hemisphere, would go up.If the West Antarctic Ice Sheet completely melted...
- The East Coast of North America would experience sea levels more than 4 feet higher than had been previously predicted - almost 21 feet!
- The NA West Coast, and Miami, Fla., would be about 1 foot higher than that -- 22 feet!
- Most of Europe would have seas about 18 feet higher!
"If this did happen, there would also be many other impacts that go far beyond sea level increase, including much higher rates of coastal erosion, greater damage from major storm events, problems with ground water salinization, and other issues," says Peter Clark, a professor of geosciences at Oregon State University.. "And there could be correlated impacts on other glaciers and ice sheets in coastal areas that could tend to destabilize them as well."
Many coastal areas need to plan for greater sea level rise than they may have expected.
But projections say this might not happen for hundreds of years...or? One thing that has become the norm is that climate changes are happening faster than scientists have projected. Partially because we don't understand all the intricacies of the global systems, and partially because the human factor is affecting imbalances faster and faster. And change is exponential. And we don't know much about earth's long term cycles. And the universe is always in flux. And...
Risk management? Sometimes we just have to do the best we can do to help prevent the unthinkable. Do the right thing. And that right thing is probably a much more conservative approach to life styles, the ways we do business...and community planning. A simpler life might be the right thing to do...for many reasons.
Sea Level Change Projections
Both digital images and video of the impact around the world of sea level increases up six meters can be obtained at this web site: www.cresis.ku.eduA digital image of what Antarctica would look like if it consisted only of land actually above sea level is also available at this URL: oregonstate.edu
SOURCE: Read more at OregonState.EDU
Publication Date: 2/6/2009
