October 04, 2013
Marine scientists have warned that our oceans are declining more rapidly than previously thought – becoming ever warmer and more acidic and losing oxygen at an alarming rate.
“We have been taking the ocean for granted,” states a report that warns of a “deadly trio” of ocean warming, acidification, and oxygen loss.
“We are… exposing organisms to intolerable evolutionary pressure,” it said. “The next mass (species) extinction event may have already begun.”
The scientific review by the International Programme on the State of the Ocean (IPSO) and the International Union for the Conservation of Nature cautioned of unprecedented ocean acidification as humans keep burning oil and coal and pump out carbon dioxide (CO2) – about a third of which is absorbed by the sea.
Today’s rate of carbon release, about 30 gigatonnes of CO2 per year, was at least 10 times faster than that which preceded the last major species extinction on Earth about 55 million years ago, it said.
The level of ocean acidification is unparallelled in at least 300 million years, said the review released just a week after the UN’s Intergovernmental Panel on Climate Change said the ocean was absorbing more than 90 per cent of the heat trapped on Earth by greenhouse gas emissions.
The new report said the average upper ocean temperature has increased by 0.6 degrees Celsius over the last 100 years. Further warming will likely cause the disappearance of Arctic summer sea ice, further oxygen depletion and the release of Earth-warming methane trapped in the Arctic seabed.
It also warned of a fast drop in dissolved oxygen in seawater – with predictions of a 1-7 per cent decline by 2100 caused by the effects of global warming and nutrient runoff into the sea from agricultural fertilisers and sewage.
“It is the simultaneous occurence of the ‘deadly trio’ of acidification, warming and deoxygenation that is seriously affecting how productive and efficient the ocean is,” said a summary of the reports that make up the review.