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https://scmp.com/news/china/science/article/3040738/chinas-deep-sea-prospectors-may-find-key-marine-heatwaves
China/ Science

China’s deep sea prospectors may find key to marine heatwaves

  • Hong Kong scientist postulates volcanic activity in the Indian Ocean has caused Australia’s bush fires
  • Chinese research vessels could help to answer this and other questions as they hunt for minerals
A scientist has linked Australia’s bush fires to a rise in water temperatures in the Indian Ocean caused by a volcanic eruption. Photo: AFP

Chinese scientists scouring the seabed for minerals and other resources are also gathering environmental data which may increase understanding of marine heatwaves and their impact on global weather events.

Professor Zhai Shikui, a marine geoscientist with the Ocean University of China in Qingdao, Shandong province in eastern China, said a large number of research vessels had been deployed in the Indian Ocean as part of Chinese exploration under a UN prospecting licence.

“Our main focus has been minerals and other resources but lots of environmental data has been collected at the same time. Some of it might hold the key to answer interesting questions about underwater heating,” Zhai said.

One question the Chinese research vessels could help to answer was raised by a retired Hong Kong professor writing in the latest issue of Imperial College London’s Imperial Engineer journal.

Wyss Yim, previously a geoscientist with the University of Hong Kong, has been tracking geothermal activity beneath the world’s oceans through satellite data and has traced a dramatic rise in seawater temperature to a volcanic eruption near Madagascar in spring 2018.

The volcano, on the sea floor off the French island of Mayotte, caused numerous earthquakes but also created a mountain of magma – about 800 metres (2,600 feet) tall and 5km (three miles) wide – according to French scientists led by Marc Chaussidon, director of the Institute of Geophysics in Paris, who said it “was built from zero in six months”.

Yim’s study found the formation of the magma mountain had coincided with the temperature rise in the southwest Indian Ocean. He hypothesised that magma from the volcano had risen from the sea floor and ridden long distances on currents before spreading out when it reached the surface.

Yim said the resulting marine heatwave was a “Blob” – a phenomenon previously recorded in the Pacific and named after 1950s horror filmThe Blob about an alien monster which devours everything in its path. He said he believed the activity led to a positive phase of the Indian Ocean Dipole – also called the Indian Nino, after the El Nino effect in the Pacific which is linked to a periodic warming in sea surface temperatures.

The warmer temperatures in the Indian Ocean caused massive drought in the southern half of Australia, with the southeast of the country worst affected. Australia experienced a particularly dry summer, with water restrictions introduced for Sydney in May, followed by unprecedented bush fires in the spring.

The east coast of southern Africa took a hit too, Yim said, with a record 10 intense cyclones last season. The biggest of them, Idai, killed more than 1,300 people and caused US$2 billion worth of economic damage to countries including Mozambique, Zimbabwe and Malawi.

If Yim’s hypothesis is correct, it could explain how gigantic marine heatwaves, or Blobs, occur. If the link could be established, it might change our understanding of climate change, said Yim, who questioned the existing consensus that rises in surface sea temperatures were linked to a warming atmosphere caused by human activities.

“Based on the study of the Indian Ocean Blob, regional ocean warming is better explained by submarine volcanic eruptions,” he said, pointing to the pause in rising temperatures between 1998 and 2016, despite an annual increase in atmospheric carbon dioxide by two to three parts per million.

Some Chinese researchers are unconvinced about Yim’s findings. Hu Yongyun, a professor at the department of atmospheric and oceanic sciences at Peking University, said a single volcano of the reported size could not on its own have caused the massive heating over the southwest Indian Ocean.

“It simply does not have enough energy to cause such a big disruption,” he said.

The current climate change model did not consider geothermal input because it was considered negligible over a short period such as a few decades or a century, Hu said.

Taking the sea floor environment into consideration when modelling climate change would also make predictions almost impossible. To run a comprehensive model of the interactions between atmosphere and ocean surface would take China’s fastest computer nearly a year to come up with a result. Adding another group of variables to the model – even if the data was available – would be computationally impractical, Hu said.

The climate model was not perfect, but the human cause of global warming was well established by the mainstream scientific community, he said.

“Reducing carbon dioxide emissions cannot be wrong.”

Wyss Yim has been tracking geothermal activity beneath the world’s oceans Photo: Getty Images
Wyss Yim has been tracking geothermal activity beneath the world’s oceans Photo: Getty Images

Zhai said that regional heating was possible, “but the mechanism remains poorly understood due to the lack of data”.

“The Blob drifts. It makes tracking very difficult. But I am sure we will know more about it over the next few years because this has become a concern to countries such as China and the United States.”

China has deployed some of its most cutting edge marine exploration vessels to the southwestern Indian Ocean, where it was granted unprecedented rights by the UN in 2011 to explore more than 10,000 square kilometres (3,860 square miles) of the sea floor in the largest licence ever granted to a single country.

Its research vessels include the Jiaolong, one of the world’s most advanced manned submersibles capable of operating at a depth of more than 7,000 metres. It can perform a wide range of tasks including gathering samples and filming geothermal phenomena such as “black chimneys” that form when hot hydrothermal fluids mix with near-freezing seawater.