For most coral reefs along the coast of Queensland, climate change is an existential threat. As the temperature increases, coral bleaching begins, and the bright and colourful underwater world slowly fades to black and white. The Great Barrier Reef houses thousands of fish, marine mammals, and algae. But as marine temperature rises, coral bleaching intensifies, and our marine wildlife heads toward grave danger.

However, amidst the story of danger and decline, something strange is happening. New research has identified that reefs along the coast of the Mackay and Whitsunday islands are consistently surviving mass coral bleaching events, while their neighbouring reefs decline or suffer due to the increase in temperature.

But how is this possible? Dr. Chaojiao Sun, an oceanographer at CSIRO, discovered that these reefs were periodically bathed in cold water. This occurrence is a variation from a process called upwelling. Upwelling, common along the coastline, is the rising of deep seawater, magma or other liquids. The nutrient-rich cold water from the deepest part of the ocean stimulates growth and nutrition of primary producers by replacing the usually nutrient-depleted warm water at the ocean’s surface. In addition, the reefs of Pompey, Ribbon, and Swain are close to the edge of the Great Barrier Reef, and are densely packed. Their proximity to each other allows the cold water to mix with warm water, which then provides a refuge for the reefs, so they can continue thriving in their vivid, natural environment, despite the increase in temperature.

         While the world’s oceans rapidly warm, scientists at CSIRO and Science.org believe that these cooling waters could provide refuges for coral reefs until 2080, even if high emissions go up to 2-3 ℃. Safeguarding these refuges is the best chance for the survival of our reefs and even allow the repopulation of reefs in the future.

“To safeguard our refuges for the future, we look for unusually cold water in satellite temperature maps. Then we run models forward in time, to see if the cool water flows would persist in the 2050s and 2080s  in a high emissions scenario. The good news is that currents of cool water may continue at least to 2080,” said Dr Sun.

The currents that bring in the nutrition dense cold water to the surface in these refuges will continue for now. However, if climate changes continues unmonitored, deeper waters will warm to a level that corals may not tolerate or adapt.

With the frequent occurrence of intense marine heatwaves recently, Great Barrier Reef Marine Park Authority Acting chief scientist Jessica Stella, has reiterated that identifying and protecting areas of climate refugia was critical to improve the reef’s long-term outlook.

The iconic Great Barrier Reef is Australia’s most valued natural asset for its rich biodiversity and cultural significance. This beautiful ecosystem, made of more than 3000 coral reefs, is the largest coral reef system in the world. If we were to lose the Great Barrier Reef, 25% of marine life would lose their homes.  Many researchers and scientists in Australia believe we must reduce our emissions and fight climate change so we can help protect this wonderful underwater city from complete disaster.