Five ways climate change is hurting our oceans

Falling oxygen levels and increased acidification are among the major issues facing the Arab region and the wider world

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When it comes to climate change, the world's oceans are being hit particularly hard.

As the International Union for Conservation of Nature (IUCN) has said, since the 1970s the seas and oceans have absorbed 93 per cent of the heat created by global warming.

A group of Chinese and American researchers reported last week that the world's oceans appear to be warming 40 per cent faster than previous studies had forecast, and researchers have warned that the consequences for the relatively enclosed Arabian Gulf could be particularly severe.

But the world has only experience a taste of what is likely to come. A 2016 IUCN report warned that even with “dramatic” carbon-emission cuts, “it will be 50 years before warming will flatten out” because of a time lag.

Even with a total end to the release of carbon, deep oceans might still experience effects for “centuries”.

Here are the top five effects of climate change on the world's oceans.

1. Temperature rises

The world's oceans are warming by about 0.1C per decade, and temperature changes in the Arabian Gulf are close to this average, according to the Intergovernmental Panel on Climate Change.

The World Wide Fund for Nature has warned that sea warming could be the “knock-out punch” that drives some species to extinction. However, the consequences of rising sea temperatures and other climate-change effects on sea life can, to some extent, be limited by the expansion of marine protected areas.

Taking a lead, the UAE was last year ranked first globally for such areas in the Environmental Performance Index (EPI), produced by the World Economic Forum and two American universities.

Abu Dhabi has six marine protected areas, with the Environment Agency – Abu Dhabi reporting that more than 13 percent of the emirate's marine habitat is safeguarded.

2. Acidification

Oceans have absorbed much of the carbon dioxide produced by people, but this has caused them to become more acidic due to the formation of carbonic acid.

The World Wide Fund for Nature has said this makes it harder for gilled animals like squid and fish to absorb oxygen from the water.

Meanwhile, crabs and other marine animals have more difficulty in making their calcium carbonate shells because the chemical changes associated with acidification mean that there are fewer carbonate ions [charged atoms] in the water.

The United Nations Development Programme has said the cure to this is a cut in carbon emissions. However, a 2015 study by scientists in Germany indicated that even with rapid removal of carbon dioxide from the atmosphere, it would take 700 years for the acidification seen so far to be reversed.


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3. Lack of oxygen

As the seas become warmer, the concentration of oxygen in the water is falling, partly because more of it is used up by the likes of bacteria.

Also, climate change cuts the extent to which circulation sends oxygen-rich surface water into the ocean depths. Overall, oxygen levels have dropped by about two percent over the past half century.

Some creatures are unable to survive as oxygen levels fall and, in turn, animals that eat them are affected. Fish may be restricted to narrower depths of water.

The Gulf of Oman, between the Straight of Hormuz and the Arabian Sea, has one of the biggest oxygen-depleted “oxygen minimum zones” in the world and a 2018 study showed that this has increased in size significantly.

FILE - In this July 27, 2018, file photo, the Dave Johnson coal-fired power plant is silhouetted against the morning sun in Glenrock, Wyo. The Trump administration on Friday targeted an Obama-era regulation credited with helping dramatically reduce toxic mercury pollution from coal-fired power plants, saying the benefits to human health and the environment may not be worth the cost of the regulation. The 2011 Obama administration rule, called the Mercury and Air Toxics Standards, led to what electric utilities say was an $18 billion clean-up of mercury and other toxins from the smokestacks of coal-fired power plants. (AP Photo/J. David Ake, File)

4. Increases in salt levels

Rising global temperatures cause evaporation rates to increase, and it has been known for more than a decade that this has resulted in higher salt levels in some of the world's seas.

Reports by NASA citing research by the United Kingdom's Meteorological Office have said the effects sound modest, with a less than a one percent increase in salt levels in one of the most heavily affected regions, the subtropical Atlantic.

However, the consequences are significant, with ocean currents disrupted and a knock-on effect on global climate patterns. The Mediterranean area, for example, is facing a cut in the amount of rainfall it receives, an effect that comes on top of increases in temperature.

5. Rising sea levels

Perhaps the best known effect of climate change on the world's oceans is a rise in sea levels, which results from seawater expansion and ice-sheet melting.

Since the beginning of the last century, the world's seas have risen by about 20cm, and The Royal Society in the United Kingdom has reported that sea levels are likely to increase by 50cm or more by 2100.

With the seas rising by about 3.2mm a year, erosion, flooding, saltwater contamination of freshwater and other harmful effects are becoming of greater concern.

Low-lying Middle Eastern cities are particularly threatened, with Alexandria in Egypt one of those facing the greatest pressures.

But measures such as the building of bigger sea walls can limit the effects of rising sea levels.