In warmer seas, cold spells are vanishing

Oceans have cooling events, the inverse of heat waves. These can be damaging and cause mass die offs, but they can also sometimes be beneficial. A new study published by the American Geophysical Union shows that these cold spells are 25% less common and 15% less intense than they were in the 1980s. The research is one of the first of its kind to focus on marine cold spells and how climate change is impacting them.  

“Recently, studies have focused on heat waves and warm ocean temperature events, less so the cold events,” said study lead author Yuxin Wang, an ocean and climate scientist at the University of Tasmania.

The researchers undertook this study to look closely at what the ocean was like before anthropogenic climate change and how cold spells in the oceans are changing over time. 

“Extreme events, either warm or cold, can bring an ecosystem to the edge,” said Sofia Darmaraki, an oceanographer at the National and Kapodistrian University of Athens who was not involved in the study. “Establishing the oceans’ baseline climatology and sensitivity of heat waves and cold spells to temperature changes, like they did in this study, is a burning question for the community.” 

The scientists analyzed climate data on the oceans from 1982 to 2020 and confirmed that the oceans are warming. The surface water of the ocean is also becoming more variable over time, changing the patterns of hot and cold spells and making them more complicated to predict. Understanding these patterns could be vitally important because cold spells can offset the sometimes negative impact of heat waves.  

“Extreme events affect coastal communities and economies, but members of the public might not be aware of how they’re going to intensify in the future. We need to get the word out,” said Darmaraki. 

“Information about the underlying physical causes of these extreme events can help improve forecasting, which can lead to the development of early warning systems. That information can be provided to fisheries and other stakeholders, and they can collaborate on the best adaptations, the best path forward.” 

The better communities know what to expect, the better they can prepare. 

The study is published in the journal Geophysical Research Letters.

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By Zach Fitzner, Earth.com Staff Writer