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Can tropical tectonic activity trigger ice ages?

Can tropical tectonic activity...
Tropical tectonic activity, such as that occurring in Indonesia today, may have triggered ice ages in the past
Tropical tectonic activity, such as that occurring in Indonesia today, may have triggered ice ages in the past
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When tectonic sutures (orange lines) form in tropical regions (green belt), they've been found to trigger ice ages
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When tectonic sutures (orange lines) form in tropical regions (green belt), they've been found to trigger ice ages
Tropical tectonic activity, such as that occurring in Indonesia today, may have triggered ice ages in the past
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Tropical tectonic activity, such as that occurring in Indonesia today, may have triggered ice ages in the past

Carbon dioxide in the atmosphere is a major driver of shifts in the Earth's climate, as we know all too well in our currently warming world. But it also works the other way – in the past too little CO2 has been associated with triggering ice ages. Now a team of scientists has found a surprising new mechanism that could lead to a drop in CO2 and bring on ice ages: Tropical tectonic activity.

Although ice ages are clearly marked in the geological record, it's still a bit murky as to what could cause such drastic shifts in climate. Some cooling events may be the result of disrupted ocean currents or even comet collisions, but the general consensus is that reduced CO2 in the atmosphere is the most reliable way to put Earth on ice.

But what exactly causes the dip in CO2 levels in the first place? A team of scientists from MIT, and the University of California at Santa Barbara and Berkeley have now pinned the blame on tectonic activity in the tropics.

When an oceanic plate and a continental plate smash into each other, they can buckle upwards and eventually create mountain ranges like the Himalayas. The fault zones that result from these collisions are known as "sutures," and the team found that large sutures seemed to appear near the equator just before each of the last three major ice ages. The researchers suggest that that's no coincidence.

"We think that arc-continent collisions at low latitudes are the trigger for global cooling," says Oliver Jagoutz, an author of the study. "This could occur over 1- 5 million square kilometers (0.4 to 1.9 million sq mi), which sounds like a lot. But in reality, it's a very thin strip of Earth, sitting in the right location, that can change the global climate."

So what do tropical sutures have to do with global cooling? The team says that when continents collide, oceanic rocks known as ophiolites are thrust out into the open. These newly-exposed rocks can react with the carbon dioxide in the air and effectively trap it. Given a large enough suture and the right environmental conditions, this new carbon sink could pull enough CO2 out of the atmosphere to bring on a global cooling event.

By the same token, this mechanism could also be responsible for ending ice ages too. After millions of years of absorbing CO2, the ophiolites would wear away in the weather, reducing the uptake of the gas. That lets it build back up in the atmosphere and gradually warm the planet back up.

"We showed that this process can start and end glaciation," says Jagoutz. "Then we wondered, how often does that work? If our hypothesis is correct, we should find that for every time there's a cooling event, there are a lot of sutures in the tropics."

The team first noticed the connection between tropical sutures and ice ages in an earlier study, linking the mechanism to glaciations that occurred 80 million and 50 million years ago. For the new study, they looked further back, to 540 million years ago.

When tectonic sutures (orange lines) form in tropical regions (green belt), they've been found to trigger ice ages
When tectonic sutures (orange lines) form in tropical regions (green belt), they've been found to trigger ice ages

First, the researchers identified all the major suture zones on the planet today, then ran computer simulations of plate tectonics to figure out roughly when and where they formed.

During that half-billion year period to the present day, the team found three times when large sutures, some 10,000 km (6,210 mi) long, formed in the tropics. And importantly, in each case an ice age followed just a few million years later – a blip on the geological time scale.

These ice ages started around 455 million years ago in the Late Ordovician, 335 million years ago in the Permo-Carboniferous, and 35 million years ago in the Cenozoic. The team also noticed that when sutures formed outside of tropical regions, no glaciation events followed.

Today, there is one major suture zone still sitting in the tropics: the islands of Indonesia. The team says this is one of the most active carbon sinks in the world at the moment, but unfortunately, the process is likely too slow to help offset our rising CO2 emissions.

The research was published in the journal Science.

Source: MIT

14 comments
CarolynFarstrider
Very interesting idea. Let's read more about it, please!
Rumata
Wrong idea. The atmospheric CO2-level is determined by the equilibrum between the CO2-level in the oceans and the CO2-level in the air, just like in a soda water bottle. Oceans contain an enormous mass of CO2 (500 times of the CO2 in the atmosphere), hence any change in the CO2-level of the air is equalized by the oceans. That's the reason, why there is no measureable correlation between the yearly amount of human CO2 emission and the yearly increase of the CO2-level in the air. As the balance between the CO2level in the oceans and in the air is temperature-dependent, the CO2-level of the air is controlled only by the global average temperature. The global average temperature is controlled basically by the cloud formation. If we examine the polar ice samples of the recent 450 thousand years, we can easily recognize that the beginning of ice ages is accompanied by an increasing level of dust. So the most probable cause of these ice ages can be some vulcanic or meteor activities that cause high dust concentrations in the atmosphere. Given these continuously moving continental plates, one may assume that they cause periodic vulvanic activities, producing enough dust to start an ice age.
Nobody
Once again, preconceived models don't prove ANYTHING. Tectonic activity also spawns earthquakes, volcanic eruptions, and changes in ocean currents without going back to the "CO2 is the main cause" climate change theory. Just shutting down the gulf stream could have the same effect. Most of the carbon fixing in the world is done by green plants. I do think the world is warming slightly but I also think the CO2 hysteria is way overblown by those who would profit from their own self serving and ineffective solutions. Global warming is one of the least of my concerns. Overpopulation is our biggest problem but nature has cures for that too They are called war, disease and famine.
Nik
''Carbon dioxide in the atmosphere is a major driver of shifts in the Earth's climate, as we know all too well in our currently warming world.'' is total political rubbish! The only main climate controller for the Earths climate is the SUN! Over the last 600 million years atmospheric CO2 has varied from 17 times present to the present low, of 400 ppm. Global temperatures have varied entirely independently of CO2 over that period. The Ice Ages that reached their lows at approximately 150 million year intervals, at 450 Million Years Ago, 300 MYA, 150 MYA, and NOW can be easily explained, and it has zero to do with CO2. The Earths climate is not a closed system, as the Dinosaurs found out. (Superimposed on these ice ages are the 100,000 year ripple of glacial periods, caused by Malenkovitch cycles.) The Earth orbits the sun, but the sun also orbits the centre of the galaxy, independently of the rotation of the galaxy, and at roughly 150 million year intervals, the solar system passes through the arms of the galaxy. When it does, the solar radiation reaching the Earth is attenuated by interstellar dust. The Earth may also experience, other gravitational effects, and an increase in earthquakes, volcanic action, and meteors. When the Earth cools, the release of CO2 held in the oceans diminishes. When it warms, more CO2 is released, so CO2 tends to follow the changes in global temperature changes. The present average global temperature, and throughout this interglacial period, contrary to Carbon Tax propaganda, is the coldest it has been for 270 million years, since the Permian extinction. The link below is to a graph that shows the climatic changes in temperature and CO2 over the last 600 million years, and the ice ages can be clearly seen, as can the general steady reduction of CO2, until 300 MYA, a rise, and then a steady fall to present. https://www.geocraft.com/WVFossils/PageMill_Images/image277.gif It would be funny, if it was not so sad, that so much learned scientific rubbish is being produced, just so that desperate climate scientists can maintain their funding.
Catweazle
Rumata says "The atmospheric CO2-level is determined by the equilibrum between the CO2-level in the oceans and the CO2-level in the air, just like in a soda water bottle." Exactly correct. Mankind can no more *significantly* affect the temperature of the Earth's surface than *significantly* change the time the Sun rises and sets.
ADVENTUREMUFFINffin
Well written article. Thank you. Interesting idea. Good to read at the end the notation that the suture zone in Indonesia is not adequate to offset the CO2 currently bleed into the atmosphere from fossil fuel burning. For that, shifting to renewable sources of energy is required.
JustJim
They may have considered the correlation between the price of postage stamps and the rising level of CO2 as well. Could lowering the price cause a decrease in CO2? I thought the relation between ocean temps and CO2 was somewhat understood, with CO2 following a rise in ocean temps by 800 years.
Douglas Bennett Rogers
No one mentioned the feedback loop that exists with land vegetation. Trees absorb solar energy and use it to evaporate water pumped from the ground. The path length water impedes the radiation of heat to space. The Earth gets warmer and more trees can grow. The surface of a lifeless Earth would average about 0 C.
EZ
When scientists are forced to pander to the keepers of the gold, it's time to take a closer look at the profession and the structure of their remuneration avenues. It appears that the current money driven system is contaminating the outcomes.
Gregg Eshelman
@Nik There's also the wobble of Earth's axis which affects the latitudes where the various climate zones are. Less tilt = overall more temperate climate. The axis has been tilting to less angle for several thousand years and will continue to do so for several thousand more. It wobbles back and forth a bit but is currently doing a two steps less, one step more 'dance'. The minimum and maximum angles Earth's axis can reach are theoretical. Nobody had the knowledge, equipment etc. to record what the tilt angle was at its last maximum. Then there's the precession of the axis, which controls where in Earth's orbit the seasons happen. Currently the northern winter is at perihelion while the southern winter is at aphelion. That puts the northern winter considerably closer to the sun than winter in the south. That has a moderating effect on winter in the northern hemisphere. Why southern hemisphere winters aren't colder is due to the massive heat sink of the oceans, that cover much more of the southern hemisphere than they do in the northern hemisphere. Thousands of years from now, the precession will reverse this, that will make northern winter at aphelion and southern winter at perihelion. That will have the north hotter in summer while southern summers will be a bit cooler. Conversely, northern winters will get quite a bit cooler - occurring when Earth is farthest from the Sun, compounded by the lack of the ocean heat sink. The north will be even more dependent on ocean currents to carry heat up from the south. In a flip from the land:ocean area ratios, the poles are in the opposite situation. During the continuous dark time of winter, the Arctic gets heat input from both air and water convection. The Antarctic, which is almost entirely covered by Antarctica, can only get heat from air convection during winter. At the current location of the Antarctic Circle, there's just a few narrow strips of ocean along the coast of Antarctica within the circle. As the axis tilt decreases, the Antarctic Circle will move to be entirely over land. Then on top of the cycles of axial tilt and precession is the variable eccentricity of Earth's orbit. Theory says it's currently around halfway between being considerably more eccentric and almost perfectly circular. Even at its most circular there will still be a significant difference in distance to the Sun between Aphelion and Perihelion. But to the Anthropogenic Global Warming Climate Change Carbon Dioxide From Human Activity is the Worst Thing Ever bunch, none of that mechanical monkey motion, nor the Sun's variable radiation output, has one iota of influence on Earth's climate.