‘Dead zone’ larger than Scotland found under Arabian Sea, and it’s growing

30 Apr 2018

Image: Pakhnyushchy/Shutterstock

A group of underwater robots scouring the Sea of Oman has confirmed the existence of a huge ‘dead zone’ where no life exists, and it’s only getting bigger.

Our seas and oceans face irreversible damage as a result of climate change, most noticeably with the mass bleaching of coral in various parts of the world.

Now, new research into the appearance of ‘dead zones’ – where there is little to no oxygen in the water – has found something that should make everyone sit up and take notice.

Future Human

In a paper published to Geophysical Research Letters, a team from the University of East Anglia (UEA) revealed that it deployed two underwater robots in the Sea of Oman (Arabian Sea) after attempts to analyse it were hampered by piracy and geopolitical tension.

As small as a human diver, these robots can reach depths of 1,000 metres below sea level for months on end, covering thousands of kilometres.

As they travelled across the region, the robots constantly sent back information on oxygen levels and the ocean mechanics that transport it from one area to another.

Now completed, the team was able to reveal the startling discovery that, while they expected to find some oxygen, the reality is far grimmer, with an area larger than Scotland shown to have almost no oxygen left.

This would make it the largest and thickest dead zone in the world.

While oxygen levels are quite low naturally in warm seas at depths of between 200 and 800 metres, climate change and the effects of fertiliser and sewage running off the land into the seas is making this far more common.

Researchers are now worried about possible implications elsewhere because for more than 50 years now, there has been no data collected in the Sea of Oman due to how difficult it is to send ships there.

‘The ocean is suffocating’

“Our research shows that the situation is actually worse than feared – and that the area of dead zone is vast and growing. The ocean is suffocating,” said Dr Bastien Queste from UEA’s School of Environmental Science.

“Of course, all fish, marine plants and other animals need oxygen, so they can’t survive there. It’s a real environmental problem, with dire consequences for humans, too, who rely on the oceans for food and employment.”

Further worry can be found in the fact that when oxygen is absent in seawater, the chemical cycling of nitrogen changes dramatically, causing greater amounts of the potent greenhouse gas nitrous oxide to be produced.

Computer simulations of ocean oxygen show a decrease in oxygen over the next century, and growing oxygen minimum zones.

However, these simulations have a difficult time representing small but very important features such as eddies, which impact how oxygen is transported.

Colm Gorey was a senior journalist with Silicon Republic