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• In January 2025, over 30,000 fish died off the coast of Western Australia due to marine heatwaves (MHWs).
• These events were made up to 100 times more likely because of climate change, according to a recent analysis.
• The heatwaves began in September 2024 and are still ongoing in the region.

What Are Marine Heatwaves (MHWs)?

• A marine heatwave is an extreme event where the sea surface temperature rises by 3–4°C above the average for at least 5 consecutive days.
• These heat waves can last for weeks, months, or even years.
• They are harmful to marine life and ecosystems, and In the past 40 years, the frequency of marine heatwaves has more than doubled due to global warming.

Why Have Marine Heatwaves Intensified?

• The primary reason for marine heatwaves is climate change.
• As the Earth's temperature has risen by 1.3°C above pre-industrial levels, the oceans have absorbed most of the excess heat—around 90%.
• This warming of the oceans leads to sea surface temperatures (SST) rising, contributing to the occurrence of MHWs.
• Since the 1800s, the global mean sea surface temperature has increased by nearly 0.9°C, and in the last 40 years, it has risen by approximately 6°C.
• In Western Australia, for example, the average temperature anomalies were about 2°C above average in September 2024.
• By January 2025, these anomalies had exceeded 2°C on three separate occasions.
• If global temperatures rise by 2°C, marine heatwaves could become 23 times more likely than they are today.

The Impact of Marine Heatwaves

• One of the most significant impacts of MHWs is the occurrence of fish kills, where large numbers of fish die suddenly due to elevated sea temperatures.
• This happened during the 2010–2011 heatwave in Western Australia, when extreme temperatures caused widespread fish deaths.
• Beyond fish kills, marine heatwaves are also responsible for the destruction of kelp forests.
  • Kelp forests are important ecosystems that provide food and shelter for many marine species.
  • Kelp thrives in cooler waters, and the elevated temperatures during MHWs can cause the kelp to die off, disrupting the food web and habitat for countless marine species.
• Another major impact of MHWs is coral bleaching.
  • Corals have a symbiotic relationship with algae that live inside their tissues.
  • When sea temperatures rise, corals expel the algae, leading to the loss of their vibrant color. This is known as coral bleaching.
  • Without the algae, corals become weaker, making them more susceptible to diseases and less able to reproduce.
• In 2024, Australia’s Great Barrier Reef experienced its 7th mass coral bleaching event, the result of repeated marine heatwaves.
• The economic impact is also significant, particularly for the fishing and tourism industries that rely on healthy marine ecosystems.

The Future of Marine Heatwaves

• As global temperatures continue to rise, we can expect the frequency and severity of marine heatwaves to increase.
• A study from Climate Central found that MHWs are expected to become even more intense in the coming decades, with potentially devastating impacts on marine life, coral reefs, and coastal economies.
• Efforts to reduce global greenhouse gas emissions are critical to slowing down the warming of the oceans.
• If global warming can be limited to 1.5°C above pre-industrial levels, the impact of marine heatwaves will be somewhat mitigated, though still significant.
• However, if warming exceeds 2°C, marine ecosystems will face even more extreme conditions, leading to greater loss of biodiversity and ecosystem services.

Conclusion

The intensification of marine heat waves is a clear consequence of the climate crisis. These extreme events have far-reaching impacts on marine life, ecosystems, and human economies. As global temperatures rise, marine heat waves are likely to become more frequent and severe. It is essential to continue efforts to mitigate climate change and protect the world's oceans, which play a vital role in maintaining global biodiversity and supporting livelihoods.

Source:

IndianExpress