Scientists have noticed an alarming rise in surface water temperatures in the highly eco-sensitive Sundarbans delta over the past three decades, a phenomenon they attribute to climate change.

“Specifically, the temperature in these waters has risen at the rate of 0.5 degrees Celsius per decade, much higher than that observed globally or for the Indian Ocean,” marine scientists Abhijit Mitra and Avijit Gangopadhyay said.

The signal of global warming has already been transmitted to the mangrove—dominated Indian Sundarbans. The surface water temperatures in both the sectors have shown significant rising trends, for both pre-monsoon and monsoon periods, they said.

Quantitatively, surface water temperatures in the Sundarbans have risen by 6.14 per cent in the western sector and by 6.12 per cent in the eastern sector over the past 27 years, at a rate of approximately 0.05 degrees Celsius every year, Mitra, a senior scientist at Calcutta University’s Department of Marine Science, said.

“This rate is, in fact, much higher than the observed and documented warming trends in the tropical Pacific Ocean (0.01- 0.015 degrees Celsius per year), tropical Atlantic Ocean (0.01- 0.02 degrees Celsius per year) and the planet itself (0.006 degrees Celsius per year),” they said reporting the findings in latest issue of Current Science.

The scientists observed that the rate of temperature increase was higher during 1993-2007 as compared to 1980-92.

The Intergovernmental Panel on Climate Change (IPCC) report also states that the rate of warming was higher during 1993—2007.

Along with the warming of surface water temperature, the scientists also noticed decreased salinity at the mouth of the Ganga at the at the western end of this deltaic complex, a phenomena they attribute to increased melting of Himalayan glaciers.

“The rivers in the western sector of the Indian Sundarbans — Hooghly and Muriganga — being continuations of the River Ganga, receive the snow melt water of the Himalayas.

“The Himalayan glaciers, popularly called ‘the lifelines of major Indian rivers’, have entered into the phase of deglaciation on account of global warming,” Mitra and Gangopadhyay said.

Spread over 10,000 sq km, the Sundarbans, the largest of such forests in the world, lie within the delta of the Ganges, Brahmaputra and Meghna rivers in the Bay of Bengal.

The region is famous for its natural beauty and is home to at least 260 bird species, Indian otters, spotted deer, wild boar, fiddler crabs, mud crabs, three marine lizard species and five marine turtle species. They also host threatened species such as the estuarine crocodile, Indian python and the iconic Bengal tiger.