Marine Heatwave

7.Recently the tens of thousands of fish have died off Northwestern Australia due to a large and long-lasting marine heatwave.

  • About the key highlights: The heatwave is heading south towards Ningaloo Reef and Shark Bay’s seagrass gardens.

o The heatwave began in September 2024 with ocean temperatures 3°C higher than usual off Broome.

o More than 90% of heat trapped by greenhouse gases is absorbed by the oceans.

  • Recent Observation & Impact on Ocean Life:

o Fish kill in Karratha is the most visible sign of distress.

o Bleaching observed in Kimberley coral reefs.

o Corals at Ningaloo Reef experiencing heat stress.

o Heatwave affecting the Gascoyne region (Carnarvon-Exmouth), likely spreading further south.

o Currently, 28% of the world’s oceans are experiencing heatwave conditions.

  • About Heatwave: It can be defined as a period where local excess heat accumulates over a sequence of unusually hot days and nights.

o It amplify many risks, such as health-related or economic risks, including increased human mortality, drought and water quality, wildfire and smoke, power shortages and agricultural losses.  

  • Marine Heatwave: A marine heatwave is a period of unusually high ocean temperatures and is defined by its duration and intensity. One of the most common ways that scientists measure the ocean's temperature is through sea surface temperature.
It occurs when the surface temperature of a particular region of the sea rises to 3 or 4 degree Celsius above the average temperature for at least five days.