WASHINGTON: The world’s oceans continue to warm, causing the vast mass of water that covers some 70% of the Earth’s surface to expand, raising sea levels, and adding to the damage caused by climate change.
“Increasing heat content of the global ocean dominates the energy imbalance in the climate system. Here we show that ocean heat gain over the zero to 2,000 metre-deep layer continued during 2006–2013,” says a report in Nature Climate Change on 3 February.
The researchers from America, Australia and New Zealand used temperature data collected from an array of 3,500 Argo buoys between 2006 and 2013 and found that temperatures were warming at about 0.005 degrees a year down to a depth of 500 metres and 0.002 degrees between 500 and 2000 metres.
The Argo programme allows scientists to “look below the surface”, providing a profile of the temperature and salinity of the ocean using the floats that move up and down in the water column from the surface to a depth of 2,000 metres. Argo makes visible large-scale ocean and climate features and processes that were once hidden.
Until the Argo buoys were launched some 10 years ago, coverage of ocean temperatures relied largely on ships recording the data. But the scientists say that, because of when and where it was collected, there was a strong bias to the northern hemisphere, near continental coasts and during summer. In addition, most readings were only down to 700 metres or less.
