Climate change has wiped out around 75% of one of Australia’s, most beautiful landmarks, the great barrier reef, but scientists at the Commonwealth Science and Industrial Research Organization (the CSIRO) have found an interesting phenomenon that might just save part of it: cold water.
Cold water is protecting the Ribbon Reefs in the far north and the Swains and Pompey reefs in the south from rising ocean temperatures. But how can these reefs survive, while others can’t? Well, CSIRO scientists found that the reefs surviving the heat are protected by upwellings of cool water – an upwelling is a process in which deep cold water rises toward the surface. The protected reefs are climate refuges, meaning the local conditions allow species to survive while other areas become unlivable.
How long these refuges are going to last is something we should know, and as the CSIRO scientists found out, they’re probably going to be here for a while. The scientists looked for unusually cool water in satellite temperature maps and ocean models, then ran these models forward in time to see how long they will be here. It turns out these life-sustaining flows will continue until at least 2080. This is because while the ocean surface heats up and ocean heatwaves become more common, the cool water currents and upwellings will continue until the deep waters also get too hot. This will happen if climate change continues unchecked for a long time.
It seems as though changes in ocean currents could alter the refuges lifespan, so the CSIRO scientists researched that as well. They found out that the South Equatorial Current carries warm water west toward the great barrier reef but then splits into the north flowing Gulf of Papua current and the south flowing East Australian Current. Their research found that the location of the split is moving south, although the exact speed of the movement is not well documented. This could change where current-depending coral larvae and coral eating Crown of Thorns Starfish end up. But the scientists’ modeling shows that, even with these changes, it won’t greatly affect the refuges.
Preserving more of the reef’s massive biodiversity is vital and we may be able to achieve this if we protect the refuges and keep them intact. But how do we protect the coral that doesn’t experience cold water flows? We could try to stop overfishing and reduce the number of crown of thorn starfish, which would help the fish and partly help the coral, but it wouldn’t help with the rising heat due to climate change. We have to reduce climate change. One simple way to reduce climate change is slowing down ships to about 10 knots. Not only does this reduce ships’ CO2 emissions, but it also reduces ship strikes with whales by around 50% according to Rockwood and colleagues (https://doi.org/10.3354/esr01056). With more whales comes less climate change. You can read an article by BBC about how whales help stop climate change here: https://www.bbc.com/future/article/20210119-why-saving-whales-can-help-fight-climate-change
Although the cold water saves a few reefs from bleaching, many reefs still suffer in the heat. We need to do something to protect these suffering reefs. Anything from donating to a charity to signing an online petition or trying to convince governments to do something. Anything helps.