A recent study highlights that marine heatwaves (MHWs)– prolonged periods of abnormally warm ocean temperatures, can significantly intensify tropical cyclones, making them more destructive before landfall. These heatwaves act as an energy source, accelerating the process of rapid intensification, where cyclone wind speeds increase sharply (by about 30 knots or ~55 km/h).
As a result, cyclones influenced by marine heatwaves are around 60% more likely to cause billion-dollar disasters, due to stronger winds, heavier rainfall, and higher storm surges. The findings underline growing climate risks as warming oceans increasingly amplify extreme weather events.
What are Marine Heatwaves (MHWs)?
Marine heatwaves refer to extended periods of unusually high sea surface temperatures in a specific ocean region.
- Characterised by:
- Duration: Several days to months
- Intensity: Temperature anomalies of +1°C to +3°C above seasonal averages
- Represent significant deviations from normal ocean temperature patterns
Factors Influencing Marine Heatwaves
- Climate Change: Oceans absorb over 90% of excess global heat, raising baseline temperatures
- Ocean Currents: Transport warm water masses into cooler regions
- Atmospheric Pressure Systems: Influence wind patterns that regulate ocean cooling
- Climate Oscillations: Events like El Niño elevate sea surface temperatures and trigger large-scale MHWs
Formation Mechanism
Marine heatwaves develop when natural ocean cooling processes weaken:
- Weakening Winds: Reduced evaporation and less mixing of surface and deep waters
- Ocean Stratification: Warm surface layer becomes trapped and isolated
- Increased Solar Heating: Thin surface layer absorbs more heat, creating localized “heat domes” in oceans
Impact on Tropical Cyclones
- Rapid Intensification (RI): Wind speeds increase sharply (~55 km/h) in a short duration
- Greater Damage Potential: Cyclones influenced by MHWs are 1.6 times more likely to become high-cost disasters
- Stronger Storm Systems:
- Higher maximum wind speeds
- Increased precipitation rates
- Enhanced storm surges
Wider Implications of Marine Heatwaves
Climate and Disaster Risks
- Amplify extreme weather events and prolong storm duration
- Slow down cyclone decay after landfall
Economic Impact
- Increased infrastructure damage and financial losses
- Example: Hurricanes like Hurricane Helene and Hurricane Milton
Biodiversity and Ecosystem Effects
- Disrupt fish breeding and migration patterns
- Cause mass die-offs of cold-water species
Harmful Algal Blooms
- Warm waters promote toxic algae growth
- Release toxins like domoic acid, affecting marine food chains and fisheries
Ecosystem Degradation
- Trigger coral bleaching events
- Destroy kelp forests, which act as carbon sinks and marine nurseries