Oceans absorb record heat in 2021

With warmer waters have come more extreme weather events, from hurricanes to heat blobs.

Graveyard of Staghorn coral
Graveyard of Staghorn coral, Yonge reef, Northern Great Barrier Reef. Rising global temperatures could have disastrous impacts on ocean circulation. Image: ARC Centre of Excellence for Coral Reef Studies, CC BY-ND 2.0

The Earth’s oceans yet again absorbed record high levels of heat in 2021 as part of a steady and dangerous 63-year warming trend fuelled by human-generated greenhouse gas emissions, concluded a recent study authored by researchers from China, Italy, and the United States.

Published last week in the journal Advances in Atmospheric Sciences, the analysis confirmed that the rate at which oceans have been absorbing heat, especially over the last 40 years, would be impossible in the absence of carbon emissions produced by human activity, reported the Washington Post.

The “long-term upward trend” has shown dramatic increases in recent years, with the oceans warming eight times faster since the late 1980s than in the three previous decades, said study co-author John Abraham, a professor of thermal engineering at the University of St. Thomas in Minnesota.

“We have built up so much greenhouse gas that the oceans have begun to take in an increasing amount of heat, compared to what they previously were,” he told the Post.

Analysing data from a planet-spanning network of buoys placed in seven ocean basins, the research team found that “the upper 2,000 metres of the Earth’s oceans absorbed more than 227 excess zettajoules of energy, compared with the 1981-2010 average.”

“Last year broke the previous record set in 2020 by at least 14 zettajoules,” added the Post.

The oceans store “more than 90 per cent of the Earth’s net heat gain due to greenhouse gases,” noted lead author Lijing Cheng, associate professor of atmospheric physics at the Chinese Academy of Sciences. “The record ocean warming in 2021 is strong evidence that global warming continues.”

With warmer waters have come more extreme weather events, from hurricanes to heat blobs. 

“For every 1.8 degrees of warming, heavy rain events will intensify by about 7 per cent,” the Post reported. The past year “marked one of the wettest years on record for the East Coast, thanks to a slew of tropical storms and summer thunderstorms.”

There was also unusual tornado activity in 2021, including two outbreaks in December in the southern and central United States, The twisters occurred in the same week that “record warm temperatures in the Gulf of Mexico created an atmosphere more reminiscent of spring than winter.”

Citing 100 years of data on conditions off the coast of Southern California, retired ocean researcher Linda Rasmussen told the Post that a series of recent ecosystem-ravaging marine heat waves in the north Pacific are very likely a result of rising ocean temperatures.

“The coastal ocean temperatures that have broken records repeatedly in recent years would not have broken records without the underlying warming trend that has been in place for many decades,” Rasmussen said.

And then there is the link between warming oceans and rising sea levels. Study co-author and Pennsylvania State University climate scientist Michael Mann told the Post that warming in the Southern Ocean “is destabilising Antarctic ice shelves from underneath, which could lead to the collapse of large pieces of the ice sheet such as the Thwaites glacier, threatening massive… sea level rise.” 

The speed at which the world’s oceans are warming “really underscores the urgency of acting on climate now,” he warned.

Last week, NASA’s annual Global Climate Report found that 2021 surface temperatures were the sixth hottest since record-keeping began in 1880. The agency concluded that “Canada and the rest of North America had their seventh warmest year on record in 2021 with a temperature that was 1.40°C (2.52°F) above average,” heating that was likewise associated with extreme weather events, including the summer’s lethal heat wave in the Pacific Northwest, according to Global News.

This story was published with permission from The Energy Mix.

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