A new study has revealed a 240% increase in marine heatwave (MHW) days worldwide during the 2023-24 summers, marking an unprecedented rise in ocean temperatures due to climate change, El Niño, and record-low cloud cover.
The research, published in Nature Climate Change, shows that 10% of the world’s oceans recorded their highest-ever sea surface temperatures (SSTs), reaching levels four times above historical averages.
Extreme Weather and Oceanic Disruptions
The prolonged marine heatwaves had far-reaching effects, influencing global weather patterns and triggering severe storms, flooding, and cyclones:
- Heatwaves struck the UK, North America, and Japan
- Severe flooding hit Ecuador, Libya, Japan, and Australia
- The Atlantic hurricane season saw near-record storms
- MHWs intensified tropical cyclones like Gabrielle (New Zealand), Mocha (Bay of Bengal), and Remal (2024)
- The Indian Ocean is experiencing alarming warming trends, with projections suggesting that heatwave days could increase from 20 to 250 days per year, pushing it into a near-permanent heatwave state.
Biological and Societal Consequences
The ecological damage from MHWs has been devastating:
- Coral bleaching and loss of vital ecosystems off Japan and Peru
- Mass fish deaths in the Gulf of Thailand and Gulf of Mexico
- Disruptions in marine food webs, leading to reduced fish and seabird populations
- Increased whale and dolphin strandings in the South Pacific
- Diseases threatening species like the Mediterranean fan mussel
Beyond the environmental toll, marine industries suffered heavily. Coral reef tourism declined, aquaculture faced losses, and Peru’s commercial fisheries shut down due to anchovy range shifts, causing $1.4 billion in losses.
Despite the alarming rise in MHWs, the world remains unprepared. The study found that most affected regions lacked response plans due to limited resources, institutional gaps, and poor communication.
With climate change accelerating, researchers stress the urgent need for global adaptation and intervention strategies to mitigate the biological, physical, and economic risks of marine heatwaves.