"It is very hard to measure volume changes in
glaciers. People are required to put stakes in the glacier and come back a year
later to see how much of a change there is in the height of the glaciers," said
Hall. She said that this is a very labor-intensive activity and is done on very
few glaciers in the world. The only way to make sure the glacier is pulling
back due to a loss of mass is to study it over a period of many years.
On average, scientists are finding that glaciers across the globe are steadily
shrinking, said Hall. These findings confirm suspicions that the world is
heating up. Researchers generally believe the warming trend may be the result
of natural, cyclical changes of the Earths climate, and possibly in combination
with effects of the large-scale burning of fossil fuels by humans since
the industrial revolution. However, the cause of global warming is currently unknown.
The last time the Earth warmed extensively,
120,000 years ago, the Greenland ice sheet drained into the ocean and the sea
rose roughly 20 feet above where it is now (Williams and Hall, 1993). Such an
increase today would flood coastal communities and low-lying
countries such as Holland and Bangladesh, as well as much of the U.S.
state of Florida.
References
- Williams, R.S., and D. K. Hall, Glaciers. Atlas of Satellite
Observations Related to Global Change, R. J. Gurney, J.L. Foster and C. L.
Parkinson, Cambridge University Press, London, 401-422.
- Hall, D.K., C. S. Benton, and W. O. Field, 1994: Changes of Glaciers in
Glacier Bay, Alaska, Using Ground and Satellite Measurements, Physical
Geography, 16(1), pp. 27-41.
- Hall, D.K., R. S. Williams, and K. J. Bayr, 1992: Glacier Recession in
Iceland and Australia, Eos, Transactions, American Geophysical Union,
73(12), pp. 129, 135, 145.
- Hall, D.K., A. B. Tait, G. A. Riggs, and V. V. Salomonson, 1998: Algorithm
Theoretical Basis Document (ATBD) for the MODIS Snow-, Lake Ice- and Sea
Ice-Mapping Algorithms, pp. 1-35.
Additional References
- Sharp, R. P., Living Ice, Cambridge University Press, Cambridge, 225 p.
- Paterson, W. S. B., The Physics of Glaciers, 3rd
Edition, Pergamon Press, 480 p.
Using satellites to measure glaciers
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This scientist is
setting up instruments to observe a glacier. Because glaciers are so large, remote, and widespread,
it is impossible to measure them all from the ground, or even from aircraft. Satellites such as
Landsat-7 are used in addition. (Photograph courtesy Dorothy Hall, NASA Goddard Space Flight Center) |