Study Finds There Has Been a Rapid Decline in Oxygen in Oceans Worldwide

World’s oceans are losing oxygen rapidly, and they are gasping for breath, a report has concluded on Saturday at the annual global climate talks in Madrid.

The report was released by the International Union for Conservation of Nature with the combined efforts of 67 scientists from 17 countries. The oxygen levels in the oceans worldwide declined by roughly 2% between 1960 and 2010, the report found. The decline is called Deoxygenation. It is mostly attributed to climate change. However, other human activities are also contributing to the problem. It can happen due to so-called nutrient runoff, as too many nutrients from fertilizers that are used on farms and lawns, wash into waterways.

The decline might not seem significant because “we’re sort of sitting surrounded by plenty of oxygen and we don’t think small losses of oxygen affect us,” said Dan Laffoley, the principal adviser in the conservation union’s global marine and polar program and an editor of the report. “But if we were to try and go up Mount Everest without oxygen, there would come a point where a 2 percent loss of oxygen in our surroundings would become very significant.”

“The ocean is not uniformly populated with oxygen,” he added. For example, a study published in the journal Science found that some parts of the tropics water had experienced a 40% to 50 % reduction in oxygen.

“This is one of the newer classes of impacts to rise into the public awareness,” said Kim Cobb, a climate scientist and director of the global change program at Georgia Tech, who was not involved in the report. “And we see this along the coast of California with these mass fish die-offs as the most dramatic example of this kind of creep of deoxygenation on the coastal ocean.”

Dr.Laffoley said the planetary cycling of elements such as nitrogen and phosphorous which are, “essential for life on Earth,” can be significantly affected by this loss of oxygen in the ocean.

“What surprised me was that, as oxygen levels lowered, there would be an effect on those cycles,” he added. “We lower these oxygen levels at our peril.”

The world’s oceans are under assault because of this Deoxygenation. The oceans absorb carbon dioxide and become less basic and more acidic. In some places, it dissolves the shells of aquatic life like clams, mussels, shrimp in that sometimes called the “osteoporosis of the sea.”

Since the middle of the last century, the oceans have absorbed 93 percent of the heat connected to human-caused greenhouse gas emissions and resulted in mass bleaching of coral reefs. Apart from that, warmer water also takes up more space than cooler water, and according to NASA, this thermal expansion process has caused roughly a third of the existing sea-level rise.

Dr.Laffoley said the temperatures on land would be 65 degrees Fahrenheit, or 36 degrees Celsius warmer if the heat absorbed by the oceans since 1955 had been added to the lower levels of the atmosphere instead.

Since the late 19th century, global average temperatures have risen 2 degrees Fahrenheit, and the Paris Climate Agreement has set a goal to limit the further increases to below 3.6 degrees Fahrenheit.

However, the capacity of water to hold oxygen is less than air by volume. With the increase in ocean temperatures, the warmer water can’t hold as much gas, including oxygen, as cooler water. (For the same reason soda tends to go flat faster in the hot summer sun.)

When temperatures are warmer, the ability of ocean water to mix gets affected, and the oxygen absorbed on the top layer doesn’t get down properly into the deeper ocean. The available oxygen gets used up more quickly because marine life uses more oxygen in warm temperatures.

“The ocean is a blue heart on the planet. It’s a majority of the living space on the planet, and it’s kind of the center of our life support system,” Dr.Laffoley said. “And I think we need to really look after it because it has been looking after us.”

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