K.S.Parthasarathy
Missing footprints of A-bomb fallout in Himalayan ice fields
It means dwindling fresh water supply in future to half the Indian population
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The total area of glaciers in the Tibetan plateau may shrink by 80 per cent by 2030
Glaciers worldwide are a barometer for global warming
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Ice cores drilled from the peak of a Himalayan ice field in 2006 by researchers revealed a chilling reality. Unlike the cores retrieved worldwide, the ice cores from the Himalayan glaciers did not contain the footprints of fallout radioactivity from nuclear weapons testing.
Lonnie Thomson, distinguished professor of earth sciences at Ohio State University and a researcher from the Byrd Polar Research Centre, who led the team revealed the findings while addressing the American Geophysical Union at San Francisco on December 12, 2007.
The radioactive fallout from 520 atmospheric tests during the 1950s and early 1960s spread far and wide and deposited on various surfaces. The missing radioactivity originating as fallout from atmospheric tests during the 1950s and 1960s routinely provides researchers with a benchmark against which they can gauge how much new ice has accumulated on a glacier or ice field (EurekAlert, Dec 11, 2007). In 2006, the joint US-Chinese team drilled four cores from Naimona’nyi, a glacier 6050 metres high on the Tibetan Plateau. Missing nuclear fallout markers means that this Tibetan ice field has been shrinking at least since the atom bomb tests 50 years ago. Melting ice from the Himalayan glaciers is the source of fresh water for Ganges, Indus and Brahmaputra.
Thompson estimated that there are about 12,000 cubic metres of fresh water stored in the glaciers throughout the Himalayas.
Radioactivity signals
They release melt water each year and feed the rivers downstream. These ice fields are shrinking. If they are eventually lost, 500 million people who depend on glacier-fed streams will suffer critical shortage of water.
The radioactivity signals from strontium-90, caesium-136, tritium (H-3) and chlorine-36 were present in ice cores from Polar Regions and from tropical glaciers around the globe.
This means that the ice fields from these regions retained snow that fell during the last fifty years.
Ice cores
In 2000, Dr Thompson led a team of researchers and retrieved ice cores from Kilimanjaro’s northern ice fields. They found fallout footprints only 1.8 metres below the surface.
“By 2006, the surface of that ice field had lost more than 2.5 metres of solid ice (and hence recorded time) — including ice containing that signal.
Had we drilled those cores in 2006 rather than 2000, the radioactive horizon would be absent — like it is now on Naimona’nyi in the Himalayas” Dr Thompson said (EurekAlert, 2007). “If what is happening on Naimona’nyi is characteristic of the Himalayan glaciers, glacial melt water will eventually dwindle with substantial consequences for a tremendous number of people,” Dr Thompson warned. Researchers estimate that there are nearly 15,000 glaciers within the Himalayan mountain chain forming the main repository for fresh water in that part of the world. The total area of glaciers in the Tibetan plateau may shrink by 80 per cent by the year 2030 (EurekAlert, Dec 11).
D.P. Dobhal, a glaciologist with the Wadia Institute of Himalayan Geology, regularly measures the changes in the size and volume of the Chorabari glacier in the Himalayas (The NYT, July13, 2007).
Chorabari’s snout
Dhobhal estimated that the Chorabari’s snout (where glacier melt water empties out in to the river) retreated 29.5 ft every year for the last three years (The NYT, July 17,2007). According to the New York Times, the Indian Space Research Organization, using satellite imaging to gauge the changes to 466 glaciers has found more than a 20 per cent reduction in size from 1962 to 2001 with bigger glaciers breaking into smaller pieces each retreating faster than its parent.
Mean air temperature
Glaciers worldwide are a barometer for global warming (The NYT, July 17, 2007). The New York Times quoted a recent study which found that the mean air temperature in the northwestern Himalayan range had risen by 2.2 degrees Celsius in the last two decades, a rate considerably more than the rate of increase over the last 100 years.
The impact of global warming is getting attention worldwide. Professor Thompson based his findings on scientific observations. Other studies corroborated them.
Let us hope that Professor Thompson’s predictions may not come true; what is worrying is that it may remain so; just a hope!
K.S. PARTHASARATHY
Former Secretary, AERB
( ksparth@yahoo.co.uk)
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