As El Niño arrives, heralding above-average temperatures across the Pacific Ocean, numerous studies have charted the rise and rise (and rise) of ocean heat.
The El Niño weather pattern was declared on 11 June by the US National Oceanic and Atmospheric Administration (NOAA), after recording above-average sea surface temperatures from the central to eastern equatorial Pacific. NOAA says its forecasts predict a 63% chance of these temperatures exceeding 2C above average. (We explore what this might mean for fishers in this story)
But aside from El Niño, there is also the additional heat that humanity is generating. Oceans soak up much of this heat energy. In honour of World Oceans Day (8 June), the latest UN World Ocean Assessment was released. Synthesising the findings of 600 experts working across the world, the report notes that 16% of the increase in ocean heat content (the amount of heat stored in the ocean) since 1955 has happened in the past eight years.
Separately, the State of the Climate in Asia report from the UN’s World Meteorological Organization flags the record ocean heat content levels of last year: “Marine heatwaves affected almost the entire ocean area of Asia, with over 10 million km2 impacted during July-September.”
Over in Europe, the Copernicus Climate Change Service (C3S) has warned that last month was the second warmest on record, globally, for both land and sea.
The potential implications of all this data is revealed by a study that was published online by the journal One Earth last week. Researchers considered the year-round impacts of above-average heat from June 2023 to June 2024, by analysing 201 “ecological impact events” with links to either high sea surface temperatures or extreme weather. Over half of the events included mass marine animal death; just 2% had no detrimental recorded impacts.
“One of the clearest findings was that impacts were not confined to traditional summer heat extremes,” says Shannon Klein, the study’s lead author, a scientist at Saudi Arabia’s King Abdullah University of Science and Technology.
“We found evidence of ecological disruption across seasons, which suggests that understanding and responding to ocean warming requires year-round monitoring and assessment.”