Rising sea levels eat into India's coasts

Max Martin India Today 6 Jan 10;

Fresh evidence of rise in the level of the Indian Ocean, in line with global trends, indicates that climate change is a clear and present danger. Information shared at the 97th Indian Science Congress here on Tuesday also showed erosion of shores in Lakshadweep and change in mangrove species at the Sunderbans delta in West Bengal.

Scientists are yet to publish the new Indian data on sea-level rise and a one-to-one relationship between climate change and environmental changes are tough to establish. Still, the new findings may add to the growing body of evidence on the impact of global warming.

India has noticed extreme weather events, including heavy rains, heat waves, shrinking glaciers and disappearance of mountain springs. Satellite and tide gauge data show sea level has risen by about 9 mm between 2004 and 2008 in the Indian Ocean, suggesting an annual rise of 2.25 mm.

"It is in tune with the trends observed globally," Shailesh Naik, secretary in the department of earth sciences, said on Tuesday. He added that the data has been compiled by the Indian National Centre of Ocean Information Systems (INCOIS), a Hyderabadbased government agency that he earlier headed. The scientists used three methods: ARGOS, a satellite-aided, global ocean monitoring system using buoys; GRACE, the twin satellites of NASA and Jason 2, a US-French satellite. Global average sea level rose 1.8 mm per year at an average over 1961 to 2003.

The average rate has been faster between 1993 and 2003 at 3.1 mm, Naik sad. The International Panel on Climate Change has said melting of the polar ice is contributing to sea level rise. Its rate is expected to increase in the coming years, inundating coastal lowlands and islands. "Mountain glaciers and polar snow covers have declined, contributing to sea level rise," Naik said, citing studies showing receding and shrinking of glaciers, including in the Himalayas.Besides, the average temperature of oceans has increased to depths of up to 3,000 m. As oceans absorb most heat, this has contributed to global warming."The highest level of rise has been notice in West Bengal's Hooghly area," Naik said. "We are not sure about the factors contributing to the sea level rise. Climate change may not be the only factor," he added."Sea level rise is not a single- factor issue - it has global and local reasons and it is not easy to differentiate between the two," J. Srinivasan, chairman of the Divecha Centre for Climate Change at the Indian Institute of Science, said. "In areas like the Sunderbans, which faces a serious threat of inundation, geological reasons such as subsidence of land play a major role," he added.

Naik said:"Seashore has eroded in Lakshadweep but its actual cause is yet to be established." The mangrove vegetation in the Sunderbans delta is showing a shift, suggesting an increase in the salt content of the water. Sundari plants (Heritiera fomes) that gives the delta its name, is getting replaced with Avicennia, a saltwater type. "This shows an ingress of salt water," he said.In view of projected and notice impacts of climate change, the Indian meteorological observation system will be augmented and there will be dedicated monitoring of vital parameters, Naik added.