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| Downstream worry: Himalayan glaciers receding | | | EARLY TIMES REPORT
JAMMU, Nov 19: Himalayan glaciers that feed rivers Indus, Ganga and Brahmaputra are no longer accumulating ice, claims a study by American glaciologists, which could adversely hit crores of people living downstream of the vast mountain range.
The researchers studying high-altitude glaciers failed to pick up radioactive signals from three ice cores collected from the 19,849 feet Naimona'nyi glacier on the southern margin of the Tibetan Plateau. In some places, for some months each year, those rivers are severely depleted now, the researchers said.
In a paper published in Geophysical Research Letters, researchers from the Byrd Polar Research Center explain that levels of tritium, beta radioactivity emitters like strontium and cesium, and an isotope of chlorine are absent in all three cores.
The absence of radioactive signals in the top portion of these cores is a critical problem for determining the age of the ice in the cores, the researchers said. The signals, remnants of the 1962-63 Soviet Arctic nuclear blasts and the 1952-58 nuclear tests in the South Pacific, provide well-dated benchmarks to calibrate the core time scales.
"We have drilled 13 cores over the years from these high-mountain regions and found these signals in all but one this one," said Lonnie Thompson, University Distinguished Professor of Earth Sciences at Ohio State.
Glaciologists rely on these time markers to date the upper part of the ice cores and without them, extracting the climate history they preserve becomes more challenging. The researchers drilled three cores through the ice to bedrock at Naimona'nyi in 2006.
"When we analyzed the top 50 feet of each core, we found that the beta radioactivity signal was barely above normal background levels," said Natalie Kehrwald, a doctoral student at Ohio State and lead author of the paper.
Tritium, an isotope of hydrogen, and chlorine-36 were also both absent from the Naimona'nyi cores, she said. They were able, however, to find a small amount of a lead isotope, lead-210, which allowed them to date the top of the core.
The researchers were able to date the formation of the ice on the top of the core to approximately 1944. "That, coupled with the other missing signals, means that no new ice has accumulated on the surface of the glacier since 1944," Kehrwald said.
Thompson feared that what is happening to the Naimona'nyi glacier may be happening to many other high-altitude glaciers around the world. "I think that this has tremendous implications for future water supplies in the Andes, as well as the Himalayas, and for people living in those regions," she said. The researchers' recent work has shown similar thinning on glaciers in Africa, South America and in Asia in the past few years. |
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