Upper ocean temperatures break records for sixth year, disrupting marine ecosystems

The extent of arctic sea ice has decreased in all seasons (Shaoqing Wang)

(CN) – Ocean temperatures around the world have risen for the sixth year in a row.

According to a study published Tuesday in the journal Advances in Atmospheric Sciences, scientists from 14 institutes around the world have found that 2021 has broken the record for heat accumulated in the upper ocean. The upper ocean absorbs 20-30% of human carbon dioxide emissions.

“The heat content of the oceans is increasing steadily, globally, and it is a primary indicator of human-induced climate change,” said author Kevin Trenberth, eminent researcher at the National Center for Atmospheric Research.

Trenberth said in an interview that the impacts of rising ocean temperatures could have serious ramifications across the globe. He noted that increasing temperatures allow the atmosphere to leach more moisture. This increases the severity of forest fires and droughts in areas already at risk, while increasing the strength of storms, hurricanes and flooding in other areas.

The threat to marine life and ecosystems is also serious. Trenberth said rising temperatures in the upper ocean can exacerbate ocean stratification where different ocean levels do not mix together as well, thereby inhibiting the exchange of oxygen and nutrients. vital between the depths and shallows. Trenberth further noted the impacts of marine heat waves on populations of fish, whales, seals and other marine species.

The 23 researchers used two international datasets from the Institute of Atmospheric Physics and the National Centers for Environmental Information, which help scientists analyze the thermal content of the oceans up to the 1950s. According to a statement accompanying the report, they found that in the past year, the top layer of the ocean – about 6,560 feet – absorbed 14 zettajoules more than in 2020. This is equivalent to 145 times the electricity produced globally in 2020. All of the energies humans use across the world in a single year is about half a zettajoule.

Trenberth said research shows climate change “is keeping pace.” He said measures such as the UN climate summit in Glasgow and international agreements, including the Paris climate accords, have failed to alleviate the build-up of ocean heat.

Going forward, Trenberth said more research will be done on expanding climate models, which he says have not been perfected. He and other researchers want to improve their understanding of the effects of warming on ocean depths. He said it would allow researchers to “forecast a week, a month, a year, ten years” and more, which would give more precision to the trajectories of climate change.

“Until we reach net zero emissions, this heating will continue, and we will continue to break records for ocean heat content, as we have done this year,” said article author Michael Mann, professor of atmospheric sciences at Pennsylvania State University, in a statement. . “A better knowledge and understanding of the oceans are the basis of actions to fight against climate change. “