135 - Ocean heatwaves

What are those?

Author

The Climate Mentor
April 25th, 2025 • Estimated Reading Time: 4 minutes

The ocean is boiling ♻️

Think climate change is only about melting glaciers and hot summers on land? Think again.
Our oceans are in trouble, and a new study shows that marine heatwaves now last three times longer than they did in the 1940s.

It's like the ocean has a persistent fever — and when the sea gets sick, the whole planet starts coughing.

Side-by-side diagram comparing normal ocean conditions with marine heatwave conditions. On the left, normal conditions show strong ocean mixing, cloud cover, and steady winds facilitating heat dispersion and evaporation. On the right, marine heatwave conditions include weak winds, reduced cloud cover, increased solar heating, high outgoing radiation, decreased evaporation, and weak mixing, resulting in significant heat accumulation near the ocean surface. Arrows illustrate changes in energy flow, evaporation, and water movement. The image highlights how altered atmospheric and oceanic dynamics contribute to prolonged marine heatwaves.

Normal ocean conditions vs. Marine heatwave conditions – A visual comparison

Why scientists are sounding an alarm? 🌱

According to a study published this month and reported by The Guardian, the average duration of ocean heatwaves has tripled since the mid-20th century. These events are also hotter than ever, with some regions experiencing temperature spikes of up to +5°C above normal.

A line graph titled "More Ocean Heatwaves" showing the increase in global marine heatwave days from 1900 to 2016. The graph depicts relatively stable values around 30 heatwave days per year until the late 20th century, followed by a steep rise after 1980, peaking above 60 days by 2016. Background silhouettes of fish and coral emphasize the marine context. Data sourced from Holbrook et al. 2020 and sea surface temperature datasets including HadISST, CERA-20C, ERSST, SODA, and COBE.

Surge in ocean heatwaves: Global marine heatwave days, 1900–2016

These marine heatwaves are devastating because they:

  • Destroy kelp forests, which are critical for marine biodiversity.

  • Cause mass coral bleaching, threatening reefs like the Great Barrier Reef.

  • Damage seagrass meadows, essential for coastal protection and carbon sequestration.

And it’s not just under the sea. These warming waters are disrupting monsoon patterns, altering ocean currents, and supercharging hurricanes.

Why this is important?

The ocean absorbs about 90% of the excess heat from global warming. If it's reaching its limit, we’re in for even more rapid climate shifts. This poses serious risks for industries like fishing, coastal tourism, and maritime trade.

But for forward-thinking investors, there are also clear opportunities:

  • Fund marine monitoring technologies and climate prediction platforms.

  • Back companies focused on coral reef restoration and regenerative aquaculture.

  • Look for ESG funds with real, measurable impact on ocean health and climate resilience.

Ready to dive into sustainable investing?

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