Oceans break record for highest temperatures five years in a row

Ocean temperatures have once again shattered records, a study by Advances in Atmospheric Sciences has found, warning that 2023 was the hottest on record for the world's oceans for the fifth year in a row.

A scuba diver swims near bleached coral and healthy coral at the Flower Garden Banks National Marine Sanctuary, off the coast of Galveston, Texas. AP - LM Otero

The annual research, published Thursday in the journal Advances in Atmospheric Sciences, was conducted by a multi-national team of scientists from 17 research institutes spanning China, the United States, New Zealand, Italy and France.

"The ocean heat content is relentlessly increasing, globally, and this is a primary indicator of human-induced climate change," said Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research (NCAR) in Colorado and co-author of the research, published in Advances in Atmospheric Sciences.

The year 2023 saw the beginning of a naturally occurring El Nino weather phenomenon, which warms waters in the southern Pacific and stokes hotter weather beyond.

• Oceans reached highest temperature on record in 2019

The phenomenon is expected to reach its peak in 2024, and is linked to the eight consecutive months of record heat from June to December.

Ocean temperatures globally were also "persistently and unusually high", with many seasonal records broken since April.

Marine heatwaves

These unprecedented ocean temperatures caused marine heatwaves devastating to aquatic life. This degrades coral reefs, home to a quarter of the world’s marine life and the provider of food for more than 500m people, and can prove harmful to individual species of fish.and boosted the intensity of storms.

Oceans absorb more than 90 percent of excess heat caused by human activity, and play a major role in regulating Earth's climate.

Raising sea levels

Rising temperatures have also accelerated the melting of ice shelves - frozen ridges that help prevent massive glaciers in Greenland and West Antarctica from slipping into the ocean and raising sea levels.

Antarctic sea ice hit record-low levels in 2023.

Globally, the year of 2023 was the hottest on record, with the increase in Earth's surface temperature nearly crossing the critical threshold of 1.5 degrees, EU climate monitors said Tuesday. 

(with newswires)