A major ocean current system in the Atlantic could be on the brink of collapse by 2025, new peer-reviewed research suggests.
This is especially concerning in light of the current heat extremes we are witnessing globally, including a massive departure from previous records in the Atlantic Ocean itself.
“Here we calculate when the early warning signals are significantly above natural variations,” to write physicist Peter Ditlevsen and statistician Susanne Ditlevsen from the University of Copenhagen.
“Given the importance of the AMOC to the climate system, we should not ignore such clear indicators of impending collapse.”
The Atlantic meridional overturning circulation (AMOC) is a large system of ocean currents that includes the well-known Gulf Stream and regulates the transfer of ocean heat from the tropics to the Northern Hemisphere.
As such, it affects much of the Earth’s climate. It is considered one of the major tilting elements in Earth’s climate system and has been slowing down since the mid-20th century.
If it comes to a complete halt, the monsoon seasons in the tropics are likely to be disrupted and Europe and North America will experience dangerously harsher winters. The domino effects will seriously affect entire ecosystems and our food security.
The AMOC has only been directly monitored since 2004, which is not long enough to understand the full trajectory of the current slowing trend.
So, by examining many models, the researchers identified an ocean region where sea surface temperatures most closely match ocean circulation conditions, to use as one of two less direct indicators for which data exists as far back as 1870.
The other early warning sign the researchers considered is “loss of resilience” in the system, which presents as increased fluctuations and variance — such as a spinning top’s increasing wobble before it topples over.
Using these two early warning signs to assess the state of AMOC is a bit like measuring heart rate and blood pressure to monitor heart health.
The team’s modeling suggests this all-important ocean circulation could end as early as 2025, and likely no later than 2095.
These findings are alarmingly earlier than the most recent IPCC predictions, but the early warning signs are already clear, argue Peter Ditlevsen and Susanne Ditlevsen.
Previous models have “biased toward overestimated stability of the AMOC, both of match the historical climate recordpoor rendering of the formation of deep watersalinity and glacial runoff”, the team writes in the newspaper.
In addition, the speed with which we hit this destabilizing event can also determine whether the system collapses or becomes stable again.
Given that we have not only failed to reduce the amount of greenhouse gases we have pumped into the atmosphere so far, but instead increased it, it is certainly it looks like we are busy a frightening one procedure to hit this ocean threshold powerfully and swiftly.
Previous research has suggested that previous extreme climate fluctuations or Dansgaard-Oeschger events were caused by such instability.
Previous research has also shown that changing just one parameter, such as increasing the amount of fresh water entering the North Atlantic, can cause the system to do so divide – lead to a sudden and drastic change in the behavior of the system.
This level of sensitivity may not have been maintained in the IPCC’s assessment, as not all models that include them take it into account.
We still don’t understand all the factors that could affect this system, and other researchers have suggested elements such as the impact of cold water influx do not fully match previous climate records.
The researchers think their method, focusing on the early warning symptoms, avoids the need to fully understand these drivers, but note they can’t rule out some unknown unknowns create a different result. They also cannot distinguish between a partial or complete collapse of the AMOC, they explain.
“Even with these caveats, this is indeed a worrying result, which should call for swift and effective action to reduce global greenhouse gas emissions to prevent the steady change of the control parameter towards the collapse of the AMOC,” the team said. concludes.
This research was published in Nature communication.