The robots are about the same size as a small human diver, but can reach depths of 1000 metres and travel the ocean for months, covering thousands of kilometres. That’s an area comparable to the surface of Florida (170,305 km²), and over two times larger than Scotland (80,077 km²). This mass of water, spanning a chilling 63,700-square-mile (roughly 165.000 km²) area in the Gulf of Oman, is nearly devoid of oxygen. In the ocean, these are also known as ‘oxygen minimum zones’ and they are naturally occurring between 200 and 800 meters deep in some parts of the world. One particularly worrying prospect is that as climate change makes ocean water warmer, it will be less able to hold oxygen — meaning more frequent and more intense dead zones. “Another interesting question is now that the Gulf of Oman is clearly consuming oxygen faster than it is replenished, how much of that is exported to the Arabian Sea and making the wider Arabian Sea OMZ extend and grow even more?” Queste asks. “Our research shows that the situation is actually worse than feared – and that the area of dead zone is vast and growing,” said Dr Bastien Queste, who led the research. “The ocean is suffocating.” 
 
 Dead zones are “a disaster waiting to happen,” he adds. Around the world there are more than 400 current dead zones in oceans and lakes, where water contains so little oxygen that aquatic life can’t survive. “Another problem is that when oxygen is absent, the chemical cycling of nitrogen - a key nutrient for plant growth - changes dramatically. The absence of this element also alters the local nitrogen cycle, causing nitrous oxide emissions — which is a greenhouse gas 300 times more powerful than carbon dioxide. The team combined their Seaglider data with a very high-resolution computer simulation to determine how oxygen is spread around the north-western Arabian Sea throughout different seasons and the monsoons. In an article recently published in Geophysical Research Letters, the researchers note that access to these waters had previously been limited by “piracy and geopolitical tensions.” 
 
 The paper “Physical controls on oxygen distribution and denitrification potential in the north west Arabian Sea” has been published in the journal Geophysical Review Letters.
– Robots have found the world's biggest underwater "dead zone" in the Gulf of Oman—yet another sign that such oxygen-depleted regions are only increasing worldwide, ZME Science reports. Scientists sent the remote-controlled submarines underwater for eight months and uncovered roughly 63,000 square miles with little to no oxygen in waters that link the Persian Gulf to the Arabian Sea. "Our research shows that the situation is actually worse than feared—and that the area of dead zone is vast and growing," research leader Bastien Queste says in a statement. "The ocean is suffocating. Of course all fish, marine plants and other animals need oxygen, so they can’t survive there." Such dead zones can happen naturally, the CBC notes, but they're becoming bigger and more common, mostly due to wastewater and chemical fertilizers. The run-off feeds algae blooms that suck up much-needed underwater oxygen. They also clog the gills of fish, which drain more oxygen when the fish decay and die. Climate change plays a role too, Queste says, because "warmer waters hold less oxygen." The Weather Network explains that warmer water floats on top of colder water, so the layers can't mix and allow oxygen from the air to reach down below. The latest find only adds to alarming data that the number of coastline dead zones has gone from 50 to 500 since 1950. Large dead zones are also hard to fix, and Queste doesn't sound too optimistic. "It's a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment," he says. (Meanwhile, the dying Gulf Stream could trigger a global nightmare.)