Is Earth’s Largest Heat Transfer Really Shutting Down? YouTube Video

Is Earth’s Largest Heat Transfer Really Shutting Down? YouTube Video Description

Check out Sharks Unknown: https://www.youtube.com/watch?v=AS2FdIcqlqg

With unprecedented heat waves and record-breaking global temperatures, it’s hard to believe that there might be a place on earth that has actually COOLED since the industrial revolution. But, it turns out, there is such a spot. The COLD BLOB off of Greenland mystified scientists for years, but new studies have uncovered a scary reality – this cool patch might be a warning of the impending collapse of a vital earth circulation system. And the consequences would be dire.

In this episode of Weathered, we travel to the Gulf Stream with the new PBS Terra show Sharks Unknown to experience the AMOC first hand. And we ask, what is the likelihood that the AMOC will collapse, and what would the consequences be?

Weathered is a show hosted by weather expert Maiya May and produced by Balance Media that helps explain the most common natural disasters, what causes them, how they’re changing, and what we can do to prepare.

This episode of Weathered is licensed exclusively to YouTube.

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Sources:
Ditlevsen & Ditlevsen. “Warming of a forthcoming collapse of the Atlantic meridional overturning circulation”. Nature Communications. 2023.

L. Caesar et al. “Current Atlantic Meridional Overturning Circulation weakest in last millennium.” Nature Geoscience. 2021

Chengfei He et al. “A North Atlantic Warming Hole Without Ocean Circulation.” Geophysical Research Letters. 2022.

Stefan Rahmstorf et al. “Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation.” Nature Climate Change. 2015.

Paul Keil et al. “Multiple drivers of the North Atlantic warming hole”. Nature. 2020.

David Armstrong Mckay et al. “Exceeding 1.5°C global warming could trigger multiple climate tipping points”. Science. 2022

Is Earth’s Largest Heat Transfer Really Shutting Down? Automated Transcript By Speak

Oceans absorb around 90% of the heat trapped by rising greenhouse gas emissions. They warm much slower than the atmosphere because of the high heat capacity of water.So on July 3rd, 2023 when we set the record for the highest global atmospheric temperature and then broke that record on July 4th, 5th and 6th, I started to wonder what the ocean was doing. Turns out it was setting heat wave records. At the same time, the ocean

by now has warmed everywhere compared to the late 19th century. Except for one very telling exception, this cold blob, the

cold blob is one of the only places on the planet that has actually gotten colder since the industrial revolution and not just a little colder while our planet’s oceans have warmed about one °C. This cold patch in the North Atlantic near Greenland has cooled by nearly the same amount. And if you find this mysterious cold blob, a little creepy, you should because many scientists see it as a sign that a vital earth system could be near and collapse with enormous consequences.

I used to say that the probability of crossing the tipping point this century is like single digit percentage. You don’t want this to be even a 5% probability because of the consequences. Would you board an aircraft that has a 5% chance of crashing? Obviously not. And there have been a couple of recent studies suggesting that crossing the tipping point may actually happen before the middle of this century. So in the next 20 to 30 years or so,

this is the A OC one of the most important earth systems for regulating and transporting heat. In this episode, we’re going to find out how likely it is to collapse and what the North Atlantic warming hole or cold blob is all about. The term cold blob was likely coined by Stefan Rasor, a German oceanographer who first described this phenomenon in a paper published in 2015. He and his colleagues observed a patch of sea in the North Atlantic roughly the size of Greenland that in contrast to the rest of the world was cooling. At the time, there were several hypotheses about what might be causing this unusual cooling, ranging from natural variability and sea temperatures to the melting of Greenland’s ice sheet. But as more research was conducted, it became clear that the cold blob was not just a brief fluctuation or anomaly a crucial turning point in understanding the origins of the cold blob occurred when climate models actually predicted its existence. And what had previously seemed like a paradox, a cooling region and an otherwise warming ocean now appeared in models as a warning signal for one of our and it’s most important climate tipping elements.

The climate models show a weakening of what we call the Atlantic. Maron overturning circulation or a for short, it’s a thing that breaks down in the Hollywood disaster movie the day after tomorrow. You

recall what you said about how polar melting might disrupt the North Atlantic currently. Well, I think it’s

happening. Hollywood stretched. What was a relatively new scientific theory well past its limits back in 2004. But since then, a lot more research has been done. The AMOC is a giant flow of water that acts like a global conveyor belt. Unlike surface currents, the AMOC is a deep vertical overturning of the ocean and it’s driven by a process called thermo hale circulation or changes in the saltiness and temperature of the ocean. The AMOC transports warm tropical water into the North Atlantic Ocean where it cools and forms sea ice. That process leaves less salty sea ice floating on the surface and sends saltier denser water down towards the ocean floor and drives its circulation back to the south where it will eventually warm and complete the circulation. And what we know is that this globally important current is slowing.

Here’s why as Greenland’s ice sheets melt, cold, fresh water is dumped onto the surface of the North Atlantic diluting the water thus making it less dense increased precipitation in the far north and decrease sea ice formation further dilutes the ocean water. This less dense water no longer sinks as readily, which impedes the flow of warm water coming from the south. And today, the AMOC is flowing at its slowest rate in over 1000 years that warm water comes from a current in this cycle called the Gulf stream. And when I heard another PBS Terra show was going diving there, I asked if I could come along and swim in part of the largest energy transfer on planet Earth. So Jasmine, where are we and

why are we here? So right now, we’re just off the coast of Jupiter Florida. We’re actually sitting in the Gulf stream right now, which is a place where a lot of sharks gather, it’s oxygen rich. Uh There’s upwelling so that deeper colder ocean water is coming up, bringing a lot of plankton. And that’s really the base of the food chain. It’s a really what we call productive area. We’re out here in the water.

So right now we are in the Gulf stream, we’re closer to the equator so that sun’s radiation is really strong, it causes the evaporation, it causes the, the salt content in the water to get stronger, that water than is transported all the way up to Europe. And while the Gulf stream is a critical part of the amoc it’s primarily driven by surface winds and the earth’s rotation. So it won’t disappear if the AMOC collapses, but it will be affected in ways you need to know about. We’ll get to that in a minute. But first, let’s get back to the AMOC climate models are pretty certain that a warmer world means a weaker AMOC. But there’s a big difference between a gradual linear weakening and a collapse. And increasingly scientists are worried that it could collapse altogether. If you

dilute the surface waters in the north, the AMOC will get slower. It well will transport less salty water from the subtropics up to the higher northern latitudes. Thereby, the density gets even more reduced, making the amo even slower. And this is a self reinforcing positive feedback.

If you weaken that a too much, uh a fresh water cap will simply develop at the surface, the sinking motion will stop and the whole system is going to break

down. The cold blob could be evidence that the has already slowed down with less heat being transported from the south. And in turn cooling the region. And the big question is, are we heading for a collapse? But first, what’s the big deal with this overturning circulation halting?

Well, it turns out that we can get a pretty good idea of what might happen by going way back in the climate record. We

actually have some uh paleo climate evidence of what will happen when the A collapses because during the last ice age, this has happened several times this will massively change the northern hemisphere temperatures.

The amoc is currently partly responsible for relatively temperate climates in otherwise far north parts of Europe, if it collapsed, would have

significant cooling in the northern hemisphere. The more cooling, the more we move northwards. So let’s say in Germany, it might just be 2 to 3 degrees cooling. But then in northern Norway, it may go up to eight or 10 degrees of cooling.

The jet stream could also become more unstable which could cause more extreme weather events like the polar vortex or heat dome. There will

be also changes in rainfall patterns. Most alarming consequence will be the southward ship of the tropical rain belt which will affect the monsoon systems of South America and of Africa. The current West African monsoon region would basically be without zoon.

Hundreds of millions of people rely on these monsoons for food production and more. But the impacts don’t stop there. We

will see massive impacts on the marine ecosystem which are very difficult to predict what they exactly will be. But the whole marine ecosystem, the fisheries all depend strongly on the current situation with the amoc

going. And another consequence would be seen along the eastern seaboard of North America. And this is where the gulf stream comes

in the sea level. On the left hand side of the gulf stream is quite low. On the right hand side, it’s about a meter higher because of the coriolis force acting on the Gulf stream and pushing the water to the right away from the American coast. If you slow down that amoc and thereby also the gulf stream, the water on the left hand side of the gulf stream will go up leading to a massive extra sea level rise by up to a meter along North Atlantic shores. When the AMO collapses,

a meter of sea level rise would inundate significant parts of coastal cities like New York, Boston, Halifax. It wouldn’t happen quite like the tsunami me in the day after tomorrow. But that much change over the course of a few decades is still far faster than what we can prepare for. And one last scary consequence, it’s estimated that our oceans absorb about a quarter of the carbon dioxide that humans release each year. And the North Atlantic alone may absorb around 1.3 billion tons per year. About 40% of the global oceans carbon, an uptake a weaker a could significantly reduce this carbon uptake. Thus, amplifying global

warming. It has really reverberations around the world if this change in ocean circulation happens.

Ok. So now that we’re taking this seriously, what are the chances that this will actually happen?

I’ve also myself always considered it as a low probability, high impact back in the nineties and, and two thousands. But in recent times, uh there are a number of studies that really suggest that the risk is much larger and much closer actually with lower levels of warming than we have previously

thought. A new study published in July of 2023 that Doctor Warms Stor was not a part of warm, that we estimate a collapse of the AOC to occur around mid century under the current scenario of future emissions. If that estimate turns out to be true, many people alive today would see impacts like 3 ft of sea level rise in New York City before the end of this century and short of collapse. A weakening of the AMOC is also something to be concerned about. It

doesn’t have to completely shut down for us to feel impacts that will um be probably quite serious and we probably already are seeing some of those impacts over the last several years. There’s been much above normal temperatures running along eastern seaboard, which has had some big impacts on the fisheries there. And

what’s really fascinating and scary is how all of these changes will interact. There’s still a lot we don’t know the

combination of natural fluctuations in the climate system that we’ve seen many times before like El Nino, La Nina, these cycles that have been happening and and evolving over many thousands of years are being disrupted in a very rapid and difficult to predict way. This journey that we’re on into uncharted territory is really concerning.

But in a conversation about tipping points like the A OC, it’s important to remember that at this point, what we do as humans is very likely to have a bigger impact on climate change than tipping elements. Our greenhouse gas emissions are still big contribution to our warming world and that’s something that we can control. And the process of understanding the uncharted climate territory we’re in is not simple. In 2022 a paper explained the existence of the cold blob without changing or collapsing ocean currents.

That’s why the process of scientific discovery and debate is so important. So what impacts are you most concerned about? Let us know in the comments and see you next time? We want to thank Jasmine Graham for joining us on this episode. And although I haven’t fully gotten over my fear of swimming with sharks, it was great to see the amazing work she does firsthand. We filmed a lot more great stuff with Jasmine, which you can see in her new show, Sharks Unknown. There’s info in the description, check it out and thanks for watching.

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