“Marine heatwaves” is a term that is appearing more and more frequently in the media. But what exactly is this phenomenon and what are its consequences? Is it possible to develop specialised models that can predict the development of heatwaves in the oceans?
Since spring 2023, large parts of the world’s oceans have had unusually high surface temperatures. When the sea surface in an area is much warmer than normal over a long period of time, we talk about a marine heatwave. The temperatures must be higher than 90 % of the measured temperatures in the same place and at the same time over the past 30 years, and that this lasts for at least five days.
Marine heatwaves can occur anywhere on the planet, and at any time of the year, if the conditions for a strong temperature increase are particularly favourable. A great deal of research is being conducted into what creates such favourable conditions. Marine heatwaves have become more frequent and intense in recent decades, in line with global warming. This trend is expected to continue.
Extremely high ocean temperatures affect marine life. It can lead to destroyed kelp forests, dead coral reefs, and loss of fish species. Higher temperatures can also lead to algae blooms that lead to toxic mussels or increases in bacteria that can be dangerous for swimmers. Marine heatwaves can have major economic consequences, with fisheries and aquaculture industries suffering, particularly during prolonged or severe heatwaves.
Recent research has shown that temperature increases not only affect the ocean surface, but also the deeper water layers. To limit negative consequences where possible, it is of great importance to be able to predict the occurrence of heatwaves before they happen.
At the Nansen Center, this research work is well underway. We are focusing our efforts on our immediate ocean areas: the North Atlantic, the Arctic Ocean, and the surrounding seas. We are testing whether the climate model we use – NorCPM – can be used to predict marine heatwaves in these areas. We are also trying to find as much information as possible about what characterises the onset of rising temperatures by looking at previous events. In addition, we are researching the impact of heatwaves on marine ecosystems in our neighbouring oceans. We hope that our research can contribute to the prediction of such heatwaves in the near future.
Key researchers: Helene R. Langehaug, Roshin P. Raj, Annette Samuelsen, Marianne Williams-Kerslake
