Oceans absorbed a record amount of heat in 2020

Oceans absorbed a record amount of heat in 2020. Ocean temperatures reached a record high in 2020, according to an international team of scientists from 13 institutes around the world. The experts report that ocean temperatures from the surface water all the way down to a depth of 2,000 meters reached their hottest levels since 1955.

Study lead author Lijing Cheng is a professor in the Institute of Atmospheric Physics at the Chinese Academy of Sciences. 

“Over 90% of the excess heat due to global warming is absorbed by the oceans, so ocean warming is a direct indicator of global warming – the warming we have measured paints a picture of long-term global warming,” said Professor Cheng.

“However, due to the ocean’s delayed response to global warming, the trends of ocean change will persist at least for several decades, so societies need to adapt to the now unavoidable consequences of our unabated warming. But there is still time to take action and reduce our emissions of greenhouse gases.”

The investigation into ocean temperatures and salinity was focused on data from the World Ocean Database, which is overseen by the National Oceanic Atmospheric Administration. 

The analysis revealed that in 2020, the upper 2,000 meters of the world’s oceans absorbed 20 more Zettajoules compared to 2019. This amount of heat is enough to boil 1.3 billion kettles.

“Why is the ocean not boiling? Because the ocean is vast. We can imagine how much energy the ocean can absorb and contain, and, when it’s released slowly, how big the impact is,” explained Professor Cheng.

The researchers found that other effects, including ocean salinity, were amplified in the hotter upper layer of the ocean. Marine life is threatened by both the heat and the increased salinity. 

“The fresh gets fresher; the salty gets saltier,” said Professor Cheng. “The ocean takes a large amount of global warming heat, buffering global warming. However, the associated ocean changes also pose a severe risk to human and natural systems.”

“Warmer oceans and a warmer atmosphere and also promote more intense rainfalls in all storms, and especially hurricanes, increasing the risk of flooding. Extreme fires like those witnessed in 2020 will become even more common in the future. Warmer oceans also make storms more powerful, particularly typhoons and hurricanes.”

The researchers will continue to monitor rising ocean temperatures and the subsequent effects on salinity and stratification.

“As more countries pledge to achieve ‘carbon neutrality’ or ‘zero carbon’ in the coming decades, special attention should be paid to the ocean,” said Professor Cheng.

“Any activities or agreements to address global warming must be coupled with the understanding that the ocean has already absorbed an immense amount of heat and will continue to absorb excess energy in the Earth’s system until atmospheric carbon levels are significantly lowered.”

The study is published in the journal Advances in Atmospheric Sciences.

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By Chrissy Sexton, Earth.com Staff Writer