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|Glacier-melting debate highlights importance of satellites
|The intense public debate on how rapidly the Himalayan glaciers are retreating
highlights the necessity for the constant monitoring of glaciers worldwide by
Since glaciers are among the most reliable indicators of climate change and because they can have a major influence on water availability, knowledge of the recent changes and future behaviour is of great interest for climate scientists and governing bodies. A key to assess these changes or to model their future evolution is the existence of a detailed glacier inventory.
Data from satellites allow scientists to measure glacier extent in detail,
providing authoritative evidence of trends. They also allow local measurements
to be expanded to a regional scale. Considering the valuable role satellites can
play in determining the state of Earthâ€™s glaciers, the Global Climate Observing
System (GCOS) has called for the systematic monitoring of glaciers by satellites
in support of the UN Framework Convention on Climate Change. Â
The animation available in the "view images" section, based on data
acquired by Landsatâ€™s TM on 15 November 1990 and by ETM+ on 1 August 2001,
illustrates the changes in glacier extents that occurred during this time in the
region northeast of the Gangotri Glacier, situated in Garwhal Himalaya.
While most of the smaller and debris-free glaciers show considerable retreat in this period, the larger glaciers with completely covered tongues have not changed much. Several of the pro-glacial lakes have grown. Quite a few glaciers at lower altitudes are nearly free of snow in the August 2001 image, indicating a retreat that year.
ESAâ€™s ERS-1, ERS-2 and Envisat Advanced Synthetic Aperture Radar (ASAR) data are providing velocity measurements of selected glaciers. The image in the "view images" section shows the surface velocity field for the Baltoro Glacier in Pakistan based on Envisat ASAR data from 2003 to 2008.
ESAâ€™s new Climate Change Initiative, which will produce robust long-term records of essential climate variables, will build on the results of the GlobGlacier project by further improving the algorithms for glacier monitoring and continually updating the related glacier inventory information.