The world's oceans experienced the most extreme and longest-lasting marine heatwaves (MHWs) on record in 2023. Some lasted for over 500 days and spread across almost the entire planet.
The results of a study published in the journal Science showed that these anomalies were record-breaking in duration, intensity, and scale, exceeding historical norms by four times.
The greatest warming was recorded in:
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The North Atlantic, where the wave that began in mid-2022 lasted 525 days;
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the Southwest Pacific, which experienced the largest and longest-lasting thermal anomaly in history;
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The tropical Eastern Pacific Ocean, where the temperature rose by +1.63 °C during the El Niño phase.
In total, 90% of all anomalies occurred in the North and South Pacific Oceans and the Atlantic.
Heat waves have caused massive coral bleaching, disrupted marine food chains, and threatened global fisheries, putting at risk millions of people who depend on the ocean for food and income.
Scientists explain the records by a combination of factors:
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increased solar radiation due to less cloud cover,
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weakening of the winds,
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anomalous changes in ocean currents.
Together, they created conditions for overheating of surface waters on a scale never before observed.
The study authors, led by Tianyun Dong, warn that the magnitude of the 2023 heatwaves could signal profound shifts in ocean-atmosphere interactions, which could herald the approach of a climate tipping point.
