Wednesday, April 27, 2016

Emerging threat from climate change: ocean oxygen levels are starting to drop

Also, when you burn fossil fuels, you remove oxygen from the air, which will result in less being absorbed by the ocean.

Peter Hannam, Environment Editor, The Sydney Morning Herald
April 28, 2015 (Australia time)


now, some of the first evidence is emerging of what scientists have been expecting for decades: oxygen levels in some oceans are beginning to fall and widespread evidence of the trend should be evident from 2030 onwards.

Warming seas absorb less oxygen at the surface. Another effect of a changing climate is that oceans turn over less, so that oxygen at the surface has less chance of moving deeper.

Matthew Long, lead author of a study published in the American Geophysical Union's journal, Global Biogeochemical Cycles, said deoxygenation poses a major threat to marine life and is one of the most serious side-effects from a warming atmosphere.

"Oxygen is a necessary ingredient for marine life, for all sorts of marine organisms," Dr Long, a scientist with the US's University Corporation for Atmospheric Research and based in Colorado.

"The extent we care about marine ecosystems for their intrinsic value, we should care," Dr Long told Fairfax Media. "We're also reliant on these systems for food - fisheries will be vulnerable."

According to the models, the process is likely to be underway in the southern Indian Ocean and parts of the eastern tropical Pacific and Atlantic.

The study found that eastern Australia, eastern Africa and south-east Asia may be relatively spared, with impacts likely to be delayed until the next century.

The effects of lower oxygen levels will compound other harmful trends for wildlife such as oceans becoming more acidic.

"We're driving pretty massive changes in the environment - and we're not just changing one variable," Dr Long said. "We're changing a suite of variables to which marine organisms are sensitive, and basically putting significant demands on their adaptive capacities."

Dr Long said it was important for governments to invest in long-term, consistent research to help predict and manage the impacts. This role was particularly vital given observation records for much of the world's oceans are limited.

He also questioned the decision by Australia's CSIRO to cut climate monitoring and modelling programs.

The agency has trimmed the number of scientists to go from two key research programs from almost 100 to about 45, a move that has drawn wide criticism from researchers at home and abroad.

"I don't understand it, and it does seem short-sighted in my view," Dr Long said.

In the longer term, the world had to curb carbon impacts and limit global warming.

"If the carbon dioxide-driven warming continues, the trend in ocean deoxygenation is basically an inexorable component associated with that warming," he said.

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