The oceans are essential for regulating the Earth's climate and supporting diverse marine life. However, they face increasing threats from climate change, particularly through rising sea temperatures and declining oxygen levels. Marine heatwaves, defined as prolonged periods of unusually high sea surface temperatures, have become more frequent due to global warming. Simultaneously, ocean deoxygenation, driven by factors such as increased stratification and nutrient pollution, poses significant risks to marine ecosystems.

Here we examines the critical relationship between marine heatwaves and low-oxygen extreme events, highlighting the dangers climate change poses to ocean ecosystems. As global temperatures rise, the frequency and intensity of marine heatwaves have surged, leading to significant alterations in oceanic conditions. These heatwaves not only raise water temperatures but also exacerbate the depletion of dissolved oxygen levels, creating a dual threat to marine life.

Using a combination of in situ observations and sophisticated climate model simulations, we analyze how these two extreme phenomena interact in the upper layers of the ocean. Our results indicate a marked increase in the co-occurrence of marine heatwaves and low-oxygen events, particularly in high-biomass regions where the impacts are most pronounced. This trend is alarming, as the simultaneous occurrence of these stressors can lead to severe ecological consequences, including habitat degradation and loss of biodiversity.

Our study underscores the urgent need for enhanced monitoring of ocean conditions and the development of adaptive management strategies to mitigate the adverse effects of marine heatwaves and low-oxygen events. As the ocean continues to warm and lose oxygen, understanding these interactions is crucial for preserving marine ecosystems and ensuring the sustainability of ocean resources in a changing climate.