Deep beneath the waves, a powerful yet invisible system has been silently regulating life on Earth for thousands of years. It's rarely talked about, barely understood by most, and yet its sudden collapse could reshape the world as we know it.Why is it weakening now? What happens if it stops altogether? And how could something so critical remain hidden for so long? Find out in this video.From Alex McColgan and the Astrum team comes an illuminating new adventure that turns our gaze homeward. Astrum Earth invites you to rediscover the most extraordinary planet in our universe - our very own Earth.Journey with us as we explore Earth's most captivating mysteries and marvels, from the global dance of El Niño to the intricate rhythms that have sustained life for billions of years. With the same meticulous research and breathtaking visuals that define Astrum, we'll reveal our planet's stories in unprecedented detail.Narrated by James Stewart, Astrum Earth promises to transform how you see the world beneath your feet and the skies above. Because to truly understand the cosmos, we must first understand home.Discover our new Astrum Earth YouTube channel: hhttps://www.youtube.com/@AstrumEarth
Chapter 1: What are the mysterious ocean currents affecting life on Earth?
Deep in our oceans lurk a series of mysterious, invisible global ocean currents that possess the power to alter life on Earth as we know it. They're intrinsically linked, working together like giant conveyor belts to pump oxygen, life, heat, salt, nutrients seamlessly and efficiently around our blue planet. They are the unsung heroes in regulating global climate.
The systems that so often take a backseat in the climate conversation. That is, until something goes wrong. Perhaps the most influential of these ocean current systems is the AMOC, the Atlantic Meridional Overturning Circulation, a keystone of Earth's climate system. And a system scientists have warned isn't just slowing down, but could actually collapse as early as 2025.
While this has happened before, it hasn't happened for nearly 10,000 years. And there's one big difference this time. We're here. How can something so life-altering have snuck under the radar without us knowing? If the worst were to happen, what would happen to life on Earth? I'm James Stewart and you're watching Astrum Earth. Join me in this video as we find out what's going on below the surface.
Okay, so that's pretty intense, isn't it? This is the year. We're in 2025. But considering the AMOC collapse is what inspired the 2004 film The Day After Tomorrow, it doesn't feel like that is just around the corner, does it? There doesn't seem to be much coverage or even urgency on this subject. Indeed, a lot of people won't have ever heard of the AMOC.
Perhaps that's one of the big problems with a force you can't see or measure. because the truth is there have been indications that the AMOC has been slowing down for the last 60 or 70 years, as our planet has warmed. And some scientists have gone a step further, suggesting the AMOC has declined by at least 15% since 1950, and is in its weakest state in more than a millennium. The big clue?
A big cold blob that's appeared over the Northern Atlantic. Bizarrely, this region is the only place in the world that has cooled in the past 20 years or so, while everywhere else on the planet has warmed. Any guesses as to why that might be? Yeah, it's the AMOC slowing down. One of the AMOC's main jobs is to shift heat around. It's one of our planet's largest heat transport systems.
It's moving the equivalent of 50 times the amount of energy humanity uses. The same amount of energy that flows through one million power stations all at once. So when it slows down, this region gets colder.
Since 2021, the general thinking in the Intergovernmental Panel on Climate Change, the IPCC, was that the probability of crossing the tipping point for a collapse this century was less than 10%, with medium confidence.
But as recently as October 2024, 44 climate scientists from 15 countries sent an open letter to the Nordic Council of Ministers, suggesting the risk of the AMOC collapsing has so far been greatly underestimated and is higher than previously thought.
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Chapter 2: What is the AMOC and why is it critical to Earth's climate?
At least two studies analyzing state-of-the-art climate models and observations have shown that the recent North Atlantic warming hole is of anthropogenic origin and is caused by reduced northward oceanic heat transport related to greenhouse gas emissions. One of the main reasons we're able to attribute some blame towards humans, as alluded to there, is by looking back to the past.
To understand conditions before regular temperature measurements began, we must turn to proxy data. The traces of past climate change left behind in slowly accumulating archives, things like ice sheets or seafloor sediments. Proxies like the ratio of oxygen isotopes found in the microscopic skeletons that make up much of the deep floor sediment provide a record of past surface water temperatures.
The size of sediment grains on the ocean floor reveal current speeds above it and allow us to reconstruct past sea surface temperatures and other parameters. What they suggest is a long-term weakening of the AMOC since the early or even mid-20th century. Climate models have long predicted its decline in response to global warming, and the physics behind these predictions is understood.
In addition, the paleoclimatic data also strongly points to human activities as the cause, in that AMOC weakening coincides with the period of unprecedented modern global warming. In short, it's very likely that humans have significantly increased the conditions in which the AMOC is prone to being unstable. We can observe several changes here.
There's a rise in greenhouse gas emissions and arctic amplification. There's also an increasingly enhanced water cycle, intensified by more energy from the sun, which creates more extreme weather like floods and droughts. There's also more evaporation in the subtropics and more precipitation in the high latitudes. Now these things are all happening before we've ever mentioned melting sea ice.
And here comes the big one. The Greenland ice sheet is melting at a rate of around 270 billion tonnes per year, and this is what makes the water less and less salty.
The fresh water dilutes the salty water, and this is salt advection feedback, a positive feedback mechanism that affects the strength of the AMOC, as the major tipping point that ultimately leads to a slowdown or even collapse of the AMOC. In 1961, US oceanographer Henry Stommel recognized how the Atlantic water's salinity leads to an AMOC tipping point.
In other words, the AMOC flows because the Northern Atlantic is salty, and it's salty because the AMOC flows. It's chicken and egg, or in more technical terms, a self-sustaining feedback effect, which works the other way around as well. If the northern Atlantic becomes less salty because of an inflow of fresh water, the water becomes less dense and the AMOC slows down.
It brings less salt to the region, which then slows down the AMOC further. One of the most interesting things in this crazy cycle of ocean systems and currents is that the AMOC has a bit of a track record of being less than stable. In other words, it's collapsed before. And its collapse has historically been linked to some pretty extreme climate events.
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