Slowing down the conveyor belt of ocean currents that bring warm water from the tropics up to the north Atlantic is the result of a change in the weather. The consequences of the collapse of the Atlantic conveyor are looked at in our research.
The collapse of this system would cause the Earth's climate to change into a La Nia-like state. It would mean more flooding rains in eastern Australia and worse summers in the US.
East-coast Australians are used to the La Nia weather pattern. Two summers of La Nia helped warm the ocean north of Australia. The record-breaking floods in New South Wales andQueensland were caused by both.
Over the south-west of North America, there have been a lot of fires in the last few years, with the total cost estimated to be at least US$70 billion.
Earth's climate is constantly changing. Our current trajectory of greenhouse gas emissions is giving the whole system a giant kick that will have uncertain consequences that will rewrite our textbook description of the planet.
The warm tropical water in the north Atlantic helps keep the European climate mild while allowing the tropics to lose heat. The waters of the southern hemisphere can be compared to the waters of the polar regions.
Climate records show that the Atlantic overturning circulation has stopped or slowed during ice ages. When the Earth's climate is warmer, it switches on and appeases European climate.
The Atlantic overturn has been stable since the beginning of human civilization. Scientists are concerned about a slowdown that has been detected over the past few decades.
Why is it taking so long? Global warming has caused the melting of polar ice caps. Massive amounts of freshwater are dumped into the oceans when the ice caps melt.
In the past 20 years, the ice around the world has melted. That is equivalent to 10,000 liters of water in the Harbours. If global warming continues, the melt rate is going to increase.
The world's oceans would be altered by a collapse of the north Atlantic. It would deplete the oxygen in the air and starve the upper ocean of the upwelling of food and water. The implications for the marine environment would be significant.
The Atlantic overturning is at its weakest for at least the last millennium with predictions of a future collapse on the cards if greenhouse gas emissions go unaddressed.
We used a global model to look at the climate under such a collapse. We applied a massive meltwater anomaly to the north Atlantic and compared this to an equivalent run with no meltwater applied.
We wanted to look beyond the well-known regional impacts around Europe and North America and to check how Earth's climate would change in remote locations.
A huge pile-up of heat builds up just south of the equator if the Atlantic overturns.
Dry air descends over the east Pacific due to the excess of tropical Atlantic heat.
Warm water is pushed towards the Indonesian seas by the trade winds. This will help put the Pacific into a La Nia-like state.
La Nia summers are cool and wet in Australia. Flooding rain is one of the worst impacts of climate change.
The shutdown of the Atlantic would be felt as far south as the South Pole. The warm air in the west Pacific would cause wind changes to travel south toAntarctica. The low pressure system over the Amundsen Sea is deeper.
As far west as the Ross Sea, this low pressure system is believed to influence ice-sheet and ice-shelf melt.
Our climate system has never been affected by changes in atmospheric gas composition like what we are imposing today by our burning of fossil fuels.
The oceans help slow the pace of change by absorbing heat and carbon in large quantities. With sea level rise, ice melt, and a slowing of the Atlantic overturning circulation projected for this century, there is payback.
The top stories from Guardian Australia will be delivered to your inbox every morning.
The north Atlantic region will not be the only one affected by this slowdown.
We can grow a new low-carbon economy. For the second time in less than a century, the course of Earth's climate history will change as a result of doing so.
Matthew England is an associate professor at the University of New South Wales.
The article was first published on the Conversation.
All Rights Reserved © 2024
