Cool water from the deep might buy the Great Barrier Reef some time.

As climate change drives increasingly severe marine heatwaves, cooler waters rising from the depths may continue to protect certain coral regions well into the 2080s.  

The Great Barrier Reef has faced seven mass bleaching events in just 25 years, with five occurring since 2016. 

Yet some areas, like the Ribbon Reefs in the north and the Swains and Pompey reef systems to the south, consistently escape the worst damage. 

According to research from the Australian Institute of Marine Science and CSIRO, this resilience comes down to ‘upwelling’ - a natural process where cold water from the deep is pushed to the surface. 

Acting as a cooling mechanism for heat-stressed corals, these waters create small pockets of relief while neighbouring reefs struggle under extreme heat.  

The Ribbon Reefs, located off Cape York, benefit from their proximity to steep continental slopes and deep channels. 

When strong tidal currents sweep through, cool water is drawn up and mixed with warmer surface layers, providing temporary relief for the reefs. 

The Swains and Pompey reefs, located about 135 kilometres off Mackay, see a similar effect. 

Here, the East Australian Current lifts cooler water closer to the surface, which strong tidal flows then funnel across the continental shelf. As a result, sea surface temperatures around these reefs can be up to 1°C cooler than surrounding waters during the critical summer months.  

While other parts of the reef experience devastating heat stress, these “thermal refuges” offer corals a chance to recover. 

This cooling effect, the study shows, could persist even if sea surface temperatures rise by 2 to 3°C under continued high emissions. 

These regions could act as critical breeding grounds, with their corals potentially able to repopulate more damaged reefs.  

However, the protection offered by upwelling is not a permanent safeguard. 

If climate change continues unchecked, even the deep waters that feed these cooler currents will begin to warm. 

Ocean models suggest the conditions creating these refuges will persist into the late 21st century, but beyond that, corals may face temperatures beyond their ability to endure.  

The researchers note that the survival of these refuges depends on keeping them as intact as possible. 

Overfishing, crown-of-thorns starfish outbreaks and shipping damage remain major threats to the reefs, even in their remote locations. While large portions of the refuges sit within protected areas like the Great Barrier Reef Marine Park, other sections remain vulnerable.  

“Every living thing has temperature limits,” the researchers warn. 

CareerSpot This email address is being protected from spambots. You need JavaScript enabled to view it.