La Nina Weather Patterns

La Nina weather patterns occur every 3-7 years off the east coast of Australia and it looks like we're in for one in the 20/21 wet season. So what are the implications for our waterways in the Wet Tropics?

Since we produced the first annual Wet Tropics Report Card in 2016, most years have been dry, with below average rainfall. The 2020 Report Card was the first year we could assess the impacts from a relatively typical wet season. This year is the first time we have had a La Nina weather event since cyclone Yasi in 2011 and the first one for the Report Card.

However, we won't be able to assess the impacts on the condition of our waterways until 2022 due to the time lag required for quality control, scientific analysis and expert peer review.

So what can we expect to see this year?

  • Increased risk of heavy rainfall events and flash and river flooding causing soil erosion and sediment plumes in our major rivers (inshore impacts of seagrass beds and some reefs)
  • Increased risk for a greater number of tropical cyclones (severe cyclones can occur any year, not just La Ninas)
  • Increased cloud cover will reduce the risk for coral bleaching of mid-shelf and offshore reefs this summer (good thing after the 2016, 2017 and 2020 mass bleaching events).
  • Fresh water plumes also cause reefs to bleach, so increased risk for inshore reefs with a La Nina.

To find out more watch this interview with our Chair, Professor Steve Turton:


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