Measurement in the deep sea: oceans heat up faster and faster

Nearly 4000 swimming robots drift through the oceans and permanently measure the water temperature. Result: It is increasing - faster and stronger than previously thought. The serious consequences are already foreseeable.

The oceans heat up faster and faster. This is the result of a report by the Chinese Academy of Sciences in the journal Science.

The latest findings refute previous reports that global warming has been suspended in recent years. "The warming of the oceans is a very important indicator of climate change, and we have solid evidence that they are heating up faster than we thought," said co-author Zeke Hausfather of the University of California.

According to the study, the temperature of the oceans at a depth of up to 2000 meters between 1971-2010 has increased by 0.1 degrees Celsius. The IPCC review report published in 2013 was based on even lower figures, even though the figures can not be directly compared.

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Oceans absorb most of the extra heat

About 93 percent of the additional heat generated by the burning of fossil fuels in particular has so far been absorbed by the oceans. In the past 150 years, the world's oceans have absorbed about 1,000 times the amount of annual world energy consumption of heat, according to a calculation published in early January in the journal "PNAS".

The strong ocean heating causes sea levels to continue to rise, according to the researchers in the Science article. The reason for this lies in the heat-related stronger expansion of the sea water. But this effect leads to a swelling of the sea level by up to 30 centimeters. In addition, the warming of seawater leads to further destruction of the coral reefs and reduces the oxygen content in the oceans.

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Oceans: warmer water, less oxygen

Low oxygen content threatens marine animals

Oxygen levels in the world's oceans have fallen by more than two percent since 1960, according to a study by the Geomar Helmholtz Center for Ocean Research in 2017. This trend has far-reaching consequences, for example for fish or other organisms in already low-oxygen marine regions, for example because large fish in particular can not survive in low-oxygen regions. By 2100, oxygen levels could fall by as much as seven percent, according to the survey published in Nature.

More accurate numbers through marine surveillance system

The new report in Science is now based on four studies published between 2014 and 2017. An important factor in the more accurate numbers included is a marine surveillance fleet called the Argo, which includes nearly 4,000 swimming robots. According to the study, these drift through the oceans and dive every few days to a depth of 2000 meters to measure data such as temperature and pH.


Argo Swimming Robot - Map of Positions

The new analysis shows that the warming of the oceans corresponds to the measured data of rising air temperatures. If greenhouse gas emissions are not reduced, the temperature could rise by 0.78 degrees Celsius to a depth of 2000 meters by the end of the century, the study said. The climate researcher Zeke Hausfather says: "While 2018 will be the fourth warmest year since the Earth's surface has been measured, it will certainly be the warmest in the oceans - as it did in 2017 and 2016."