Friday, 22 February, 2019

The World's Oceans Are Losing Oxygen Due to Climate Change

Theresa Hayes | 17 February, 2017, 01:26

The oxygen content in the world's oceans has decreased by more than two per cent in the past 50 years and could decrease by seven per cent by 2100, a new study shows. However, past studies have found that the world's oceans have been steadily warming for half a century. However, the oxygen supply in the oceans is threatened by global warming in two ways: Warmer surface waters take up less oxygen than colder waters.

The study provides evidence that this drop in oxygen is likely to be a direct result of climate change, more specifically the rise in temperature, as warm ocean water finds it challenging to retain oxygen. As warmer air warms the ocean surface, the seas become less able to absorb and keep oxygen. "To quantify trends for the entire ocean, however, was more hard since oxygen data from remote regions and the deep ocean is sparse", Schmidtko explained in the statement.

The ocean is losing oxygen - and that could be really bad for creatures that live there. However, researchers were unable to quantify just how much.

But the oceanographers of GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, saw more than six times the oxygen drop they'd have expected if this surface absorption power were the only effect at work, according to their paper, published Wednesday in the journal Nature. But creatures in the deep might not get the oxygen they need.

By using historic oxygen data and modern ocean observations, Schmidtko and his colleagues - Martin Visbeck and Lothar Stramma - managed to build a global model that revealed oxygen levels have dropped 2 percent over the last 50 years. However, only about 15 per cent of this decrease is directly attributed to this factor, the study authors say.

A few studies have modeled the rise in ocean temperatures and resulting loss of oxygen on a small scale. Although the levels of ocean deoxygenation there are still non-critical, the phenomenon can have long-term consequences on marine life because of the uneven oxygen distribution.

The findings "should ring yet more alarm bells about the consequences of global warming", Gilbert said.

"While the slight decrease of oxygen in the atmosphere is now considered non-critical, the oxygen losses in the ocean can have far-reaching consequences because of the uneven distribution", said researcher Lothar Stramma.