The collapse of the Atlantic Current: what will be its consequences?
Great storm, sudden climate change and New York completely froze. Hollywood blockbuster movie is like this Tomorrow Described the sharp reduction of atlantic ocean circulation And its disastrous consequences.
The Atlantic Current is approaching a critical point
Although Hollywood’s view was exaggerated, the 2004 film a serious question: If global warming disrupts the Atlantic Meridional Overturning Circulation (AMOC), which is important for transporting heat from the tropics to northern latitudes, How sudden and severe will climate change be?
Twenty years after the film’s release, there’s a lot more we know about it Atlantic Ocean circulation, Instruments installed in the ocean since 2004 show that its circulation has probably slowed over the past two decades. At its weakest in almost a millennium, Studies also show that in the past the circulation reached a dangerous tipping point that sent it into acute e unstoppable fallAnd it may reach that tipping point again the planet is warming And glaciers and ice sheets melt.
A new study was produced using the latest generation of Earth’s climate models. fresh water flow Until the ocean circulation reached that tipping point.
The results showed that circulation could stop completely within a century Reaching a tipping point and moving in that direction. If this happened, average temperatures in North America, Asia and parts of Europe would drop by several degrees. the consequences will be serious And spreading all over the world.
We also discovered a physics-based early warning signal that could alert the world when the Atlantic Ocean’s circulation reaching its turning point,
What is the Atlantic current?
Ocean currents are driven by winds, tides, and differences in water density.
In the Atlantic Ocean circulation, relatively warm, salty surface waters near the equator flows towards greenland, During its journey it crosses the Caribbean Sea, meanders into the Gulf of Mexico and then flows along the East Coast of the United States before crossing the Atlantic.
How the Atlantic Ocean’s circulation changes as it slows down.
This stream is also known as Gulf Stream, brings summer to Europe. As it flows north and cools, the water mass becomes heavier. When it reaches Greenland, it begins to sink and flow southward. sinking water near greenland brings water from other parts of the Atlantic Ocean and the cycle repeats, like a conveyer belt,
A lot of fresh water could come from melting glaciers and the Greenland ice sheet dilute water salinity, preventing it from sinking, and weakening this marine conveyor belt. A weak conveyor belt transports short summer in the north and allows less heavy water to reach Greenland, further weakening its strength. Once it reaches the peak point, it stops immediately.
What happens to the climate at the extreme point?
The existence of the tipping point was observed for the first time An overly simplified model Of Atlantic Ocean circulation in the early 1960s. Today, more detailed climate models indicate a continued slowing of the conveyor belt force due to climate change. However, in these climate models It doesn’t seem like there will be any sudden interruptions of the circulation of the Atlantic Ocean.
This is where our study comes in handy. We conducted an experiment to find a detailed climate model turning point for sudden collapse Gradually increase the intake of fresh water.
Once the inflection point is reached, the conveyor belt stops in 100 years, Heat transport northward is greatly reduced, causing sudden changes in climate.
Result: extreme cold in the north
Areas affected by the Gulf Stream receive very little heat When circulation stops. Due to this, the North American and European continents become cooler by a few degrees.
The European climate is influenced by the Gulf Stream to a greater extent than in other regions. In our experiment, this meant that parts of the continent Change greater than 3°C per decade, much faster than current global warming of about 0.2 °C per decade. We have discovered that some areas in Norway will experience Temperature drops by more than 20°C, On the other hand, areas of the Southern Hemisphere will warm by a few degrees.
The annual average temperature change after the conveyor belt closure shows a sharp drop in temperatures, especially in Northern Europe.
These temperature changes develop almost over 100 years, This may seem like a long time, but on typical climate time scales, these are sudden changes.
The collapse of the conveyor belt will also have an impact. sea level and rainfall patterns, which could push other ecosystems closer to their tipping point. For example, the Amazon rainforest is sensitive to rainfall reduction, If its forest ecosystems are converted to grasslands, the transition will release carbon into the atmosphere and cause the loss of valuable carbon sinks, further accelerating climate change.
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atlantic circulation has slowed down significantly in the distant past, During the Ice Age, when the ice sheets covering large parts of the planet melted, the influx of fresh water slowed the Atlantic circulation, triggering huge fluctuations in climate.
So when will we see this turning point?
The big question – when will the Atlantic circulation reach its peak point – remains unanswered. Overview they don’t go very far back Enough to give clear results. However a recent study has shown that the conveyor belt is getting closer quickly reach its peakPossibly within a few years, these statistical analyzes made many assumptions that give rise to uncertainty.
Instead, we were able to develop an early warning sign Observational and physics-based observations related to salinity transport along the southern edge of the Atlantic Ocean. Once the limit is reached, the tipping point is likely to occur one to four decades later.
A climate model experiment shows how quickly the AMOC slows down once it reaches a critical point along the limit of freshwater entry into the ocean. It is unknown when this will happen.
Our study highlights the climate impacts severity of such sudden collapse Of conveyor belt. Changes in temperature, sea level and precipitation will seriously impact society, and climate change is unstoppable on human time scales.
It may seem counterintuitive to worry due to extreme cold As the planet warms, however, this threat looms if the main circulation of the Atlantic Ocean is choked by excess meltwater.
René van Westen, postdoctoral researcher in climate physics, Utrecht University, Henk A. Dijkstra, Professor of Physics, Utrecht University and Michael Kleefuis, climate model expert, Utrecht University
This article was originally published on The Conversation. Read the original.