You Should Be Worried About This Terrifying Ocean Discovery
We don't know what we are messing with.
The Ocean is a terrifying place. We have yet to even scrape the surface of the mysteries hidden in its dark depths. Yet, the dangers dwelling in this abyss are far scarier than any monster. Scientists recently discovered that the Ocean is about to deliver humanity a colossal dose of climate karma. You see, our obliteration of the Earth’s environment is causing the Ocean’s overturning circulation currents to slow or potentially completely collapse. For decades, we’ve known such collapses could cause hugely devastating changes in weather patterns. But MIT scientists have recently discovered that these collapses will also cause one of the few systems keeping our planet from slipping into a climate apocalypse to falter.
But let’s first start with what an overturning circulation current actually is. The most famous one is the Atlantic Meridional Overturning Circulation (AMOC), also known as the Gulf Stream. Overturning circulation currents are interlinked systems of cool deepwater currents and warm surface currents driven by winds and sea ice. You see, as sea ice forms in the poles, the water around the ice sheets gets saltier and, therefore, denser, as ice can’t contain salt. This cold, dense water sinks, drawing warmer surface waters in from the tropics. Meanwhile, trade winds in the tropics blow the warm surface waters towards the poles, which pulls cold water up from the depths of the tropics. As these two systems are linked, water goes around and around, with cold currents flowing from the Poles along the ocean floor to the tropics and warm surface waters flowing from the tropics to the Arctic.
There are many of these currents around the planet, and they play a crucial role in weather patterns and our ocean ecosystems. For example, the reason the UK is so much warmer compared to other countries at the same latitude is because it is warmed by the northward flowing warm water current of the Gulf Stream.
But, as our emissions slowly bake the planet, less and less sea ice is forming, causing less water to sink at the poles, weakening these currents. In fact, multiple studies have shown that overturning currents like the Gulf Stream area already significantly weakened. Other studies have also found that once the sea ice-driven end of the current weakens too much, it becomes unlinked from the warm end, collapsing the entire current.
So, what’s MIT’s terrifying discovery about these collapses?
Well, the world’s oceans currently absorb 30% of humanity’s carbon emissions, significantly reducing the onset of climate change. It does this through two methods.
Firstly, through tiny single-celled drifting plants, known as phytoplankton. Like trees, they build their bodies from atmospheric carbon, but unlike trees, when they die, much of that carbon sinks to the ocean floor, where it is safely stored for centuries. While small, phytoplankton is mighty, accounting for roughly 40% of the globe’s natural carbon capture and storage.
Secondly, through directly absorbing it. Carbon dioxide is soluble in water and turns into carbonic acid once dissolved. This acid then reacts to minerals dissolved in ocean water, turning it into far more stable carbonates. These carbonates sink to the ocean floor, where they are safely stored for centuries or potentially millennia.
Okay, so what’s the problem?
Well, both phytoplankton and carbonate creation rely on the upper layers of the Ocean being rich in nutrients like iron. Where does that iron come from? When the cold arm of these overturning currents drags along the ocean floor, they pick up these minerals. When this water upwells in the tropics, it brings these minerals to the surface waters and disperses them across the ocean surface layers.
MIT scientist Jonathan Lauderdale discovered this fact’s catastrophic impact accidentally. He was running climate computer simulations on weakening overturning currents and found that atmospheric carbon levels were rising way faster than expected. This actually led Lauderdale to suspect that “there was some mistake” with the simulation. But no, he discovered a new climate tipping point.
A climate tipping point is a negative feedback loop in climate systems. You see, as these overturning currents slow, the oceans will stop absorbing as much carbon emissions as they used to. In fact, vast amounts of carbonic acid that hasn’t been turned into carbonates will start outgassing, meaning the Ocean could actually flip and become a producer of carbon emissions, not a carbon sink. These added emissions, combined with the fact more of humanity’s emissions are staying in the atmosphere, will dramatically warm the planet, reducing the sea ice and further weakening these overturning currents, which means the Ocean will produce more carbon emissions and absorb less, and so on.
In short, Lauderdale has discovered that as these overturning currents stutter and fail, they can create rapid and devastating levels of climate change.
We have suspected a connection between atmospheric carbon and these overturning currents for a few years now, but this is one of the first times it has been demonstrated. The fact that we are only just understanding these relatively simple climate systems and the negative effects they could have when they fail shows that we are playing with things we don’t understand.
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Sources: Nature, Will Lockett