Other major factor is increase in melting of ice caps and giant ice sheets, says top oceanographer

A large component -- about 50 per cent -- of sea-level rise over the past half a century has been driven by the warming of oceans which are absorbing at least 30 per cent of CO2 emissions from the atmosphere, according to leading oceanographer Susan Wijfells.

The other major factor for sea-level rise, the melting of ice caps and giant ice sheets, was also increasing over the past few decades, she added.

Deployment of Argo floats

Dr. Wijfells, who is the co-chair of International Argo Steering Team (IAST), told The Hindu here on Thursday that a network of 3,000 Argo floats had been deployed across different oceans by 28 nations, including India, to study heat and mass movement in the oceans. Each of these floats delivers in real time the profile of temperature and salinity up to a depth of two km from the ocean surface.

“The key thing is it allows us to follow where the ocean is storing heat and where it is salty.”

This was important as it sets the speed at which the climate could change, she added.

Storms in winter

With the 13-year-old Argo project achieving a milestone this month in completing its one millionth profile, Dr. Wijfells said “so far we have learnt many new things.” She said by locking up “atmospheric carbon” the oceans were slowing down green house gas formation. Now it was known where a lot of surface water was getting pushed inside an ocean. A combination of winds, ocean currents, eddies and surface water saturated with gases was responsible for pushing it down.

Earlier, it was not known what the ocean looked like in winter time.

“There is a lot of exchange between the atmosphere and oceans because of storms in winter,” she said.

The data generated so far showed that saline areas were becoming more salty and fresh water places were getting increasingly fresher. It was a fingerprint showing that the water cycle was becoming more intense. This was very important for the future. As we continue to warm, the contrast between wet and dry areas would continue to increase indicating that people living in drought areas could expect more droughts.

According to M. Ravichandran, a member of IAST and scientist at Indian National Centre for Ocean Information Services (INCOIS), Ministry of Earth Sciences, short spells of high intensity rainfall were increasing in India and those of low intensity were declining, although there was not much change in the total rainfall.

Dr. Wijfells was in the city to attend the international Argo data meeting.