The study shows that marine heatwave events are likely to become more extreme in the future, even when accounting for the long-term rise of ocean temperatures due to climate change.
This is attributed to air-sea feedbacks that can modulate temperature changes within the marine heatwaves. The identified processes include reductions in clouds and ocean mixed-layer depth, and air advection, meaning air transport, from fast-warming subpolar regions. Looking at the complex interplay of these air-sea processes, they model their response to a 4 °C warmer climate. They find an overall amplification of the temperatures within the marine heatwave, particularly pronounced in the coastal and central Northeast Pacific.
Heatwaves in the ocean pose a threat to marine species and ecosystems, as temperatures can become too high for certain local organisms. Within such marine heatwaves, AWI scientists find that temperatures could increase by 50% more than the global long-term ocean warming. “The projected amplification we identified could thus place even greater stress than expected on marine ecosystems and fishery economics”, notes Marylou Athanase.