What Causes an Ice Age?
Introduction We might be closer to an ice
age than we would like to admit. And the reason is global warming. Yes I know, not so intuitive.
One might ask: “What’s the most significant consequence of global warming?” And the
response usually looks something like: “Oh, nothing much. Just the sudden
increase in sunscreen sales and polar bears getting their own air conditioning units!”
But that’s not all! The global heating of the Earth is disrupting the periodic cycle of ice
ages, that are naturally caused by its orbit around the Sun and other orbital parameters!
Let’s see what scientists have to say about what causes an ice
age and how global warming might be affecting the upcoming one!
--- What
is an Ice Age? So, what is an Ice Age? It is a
geological phenomenon that is both a blessing and a curse, kind of like finding out your favorite
guilty pleasure snack is actually good for you. On one hand, it brings forth majestic landscapes of
icy wonder, like a frozen fairytale land straight out of a Disney movie. On the other hand, it also
means freezing temperatures that make even the most die-hard penguin question their life choices.
To put it scientifically, an ice age occurs when the Earth enters a period of time where
temperatures drop significantly, causing vast sheets of ice to cover large portions of the
planet. It's like Mother Nature's way of saying, "Hey, how about we switch things up a bit and turn
the thermostat down to 'Arctic'?" Now, you might be wondering,
what kind of celestial variations cause this icy spectacle? Let’s go through them.
--- Wobbles of Earth
Imagine the Earth as a little spinning top, rotating and wobbling, almost like it’s trying
to make up a dance move. But unlike John Travolta, our planet has less defined rhythm. It sways and
turns like an ice skater who is losing balance, because of the great variations of its rotation.
You see, the Earth doesn’t rotate as perfectly as we are taught in school, where we are told that
it has an axis titled at 23.5 degrees from the vertical and it just spins around it..
I would have personally loved it if it did just that but reality is much much more complicated,
and scientists are losing sleep because of it. So throughout many “mysterious” variations,
we ended up discovering that the Earth’s spin axis has been shifting towards the east much
faster than before. This shift, accounting for almost 17 centimeters per year, is thought
to have been caused by the loss of mass from rapidly melting ice in Greenland and Antarctica.
But how are those two things related? Well, in easy words, the Universe has its way of preserving
balance. In the case of bodies that rotate, there has to be a conservation of angular momentum,
which in turn depends on the mass distribution of the object and its rotational speed.
So when ice sheets melt, the mass is redistributed from solid ice (glaciers) to liquid water in the
oceans. And this change could cause a change in the rotation of the Earth.
So, how do we test such a hypothesis? It’s easy, you just point satellites to monitor the changes
in the Earth’s mass over the years. Thanks to the GRACE satellites, we were able to measure
the amount of mass included in the cycles of water between land and oceans, and conclude
that indeed that was causing it. But not only from the poles like we thought, but also from
the Indian subcontinent and the Caspian Sea that actually had a bigger impact that we expected.
This change in tilt caused by global warming changes the cycles of variations in the Earth’s
orbital parameters, also called the Milankovitch cycles, and in turn affects when we expect our
next ice age to be. ---
If you haven’t seen our video on the crazy prediction of the Milankovitch Cycles,
go check it out! I’m sure you will like it but come back here as we have so much to unfold still!
--- Axial Precession
To understand axial precession, it’s important to consider Earth’s shape and the interactions
it has with gravitational forces. Another lie they told us in school is that the Earth is a perfect
sphere. Well guess what, no it’s not a sphere. It’s flatter at the poles and has bulges at the
equator because of its rotation. This causes an asymmetric distribution of mass and therefore
generating tidal forces on the equatorial bulge by the Sun and the Moon. The time it requires
to complete a full cycle and go back to the same axial tilt is around 27 thousand years,
causing one hemisphere to experience more extreme seasonal differences than the other.
Did you know that currently, the perihelion, which is the Earth's closest point to the Sun,
happens during winter in the Northern Hemisphere and summer in the Southern Hemisphere?
However, in about 13 thousand years, this will actually switch! This means
that the Northern Hemisphere will then experience more extreme solar radiation,
while the Southern Hemisphere will enjoy more moderate seasons. It's fascinating to
think about how our planet's climate patterns can change over such long periods of time,
isn't it? And you won’t feel the difference because your lifetime is so much shorter!
--- Eccentricity
The shape of our orbit around the Sun changes over time. That shape is what
we call eccentricity and it varies between zero, giving us a nice circular orbit, and one, where
the orbit becomes more stretched and elliptical, looking more and more like an elongated egg.
The blue planet’s orbit has a pretty low eccentricity, quite close to 0,
but here comes the interesting part. Due to the gravitational interactions of Saturn, Jupiter,
and other factors, the Earth's eccentricity can actually vary over time. This means that the shape
of our orbit changes, which in turn affects the distance between the Earth and the Sun.
And guess what? This variation in eccentricity is the reason why our seasons have slightly different
durations. Currently, summers in the Northern Hemisphere are about 4.5 days longer than winters,
and springs are about three days longer than autumns. As the eccentricity decreases,
the duration of our seasons gradually evens out. A scientist named Milankovitch studied these
variations and found something fascinating. When the Earth's orbit is at its most elliptical,
we receive about 23 percent more solar radiation at our closest approach to the Sun compared to
our farthest departure. Right now, Earth's eccentricity is near its least elliptical
(most circular) and is slowly decreasing over a cycle of about 100 thousand years.
But don't worry, the change in global annual insolation (the amount of solar
radiation reaching Earth's atmosphere) due to the eccentricity cycle is actually very small.
Since the variations in Earth's eccentricity are relatively minor, they only play a minor
role in the annual seasonal climate variations. And luckily, we have nothing to do with it.
--- Combination of the Cycles
Now that I can use these terms with the peace of mind that you will know what I am talking about,
let’s go through how they could cause an ice age on Earth together.
Specifically, combined periods of low eccentricity, a lower rotational axis tilt,
and the positioning of the closest approach to the Sun during the Northern Hemisphere winter
definitely create just the perfect environment for an ice age to form.
--- Ocean’s Circulation
The last period of ice the Earth went through was 100 thousand years ago and
lasted for around 75 thousand years! The Earth actually goes through one of
those every few million years. Right now, we are in a time called an inter-glacial period,
which means it's not as cold and the previously accumulated ice is melting.
After some scientists at Cardiff University studied icebergs that melt in Antarctica,
they found that when these icebergs melt, they release pieces of rock into the ocean.
These rocks cause changes in the ocean's circulation, which is how the water moves around!
When the Antarctic icebergs melt, a lot of fresh water goes into the Atlantic Ocean from
the Southern Ocean. This makes the Southern Ocean saltier and the North Atlantic fresher,
or sweeter, causing a change in the ocean’s circulation pattern.
Why does it affect the pattern of ocean’s circulation? Well,
that is due to the difference in density between freshwater and saltwater.
Saltwater is denser than freshwater, meaning that it has a higher concentration of salt and
is therefore heavier. When the Antarctic ice release large amounts of freshwater into the
Southern Ocean, the flow reduces the overall salt concentration in the Southern Ocean, making it
relatively less dense compared to the saltier one. As a result, the freshwater, being lighter, tends
to stay at the surface rather than sinking down into the deeper layers of the ocean. This change
in density and distribution of water affects the ocean's circulation patterns, specifically the
thermohaline circulation. This circulation is driven by differences in temperature (thermo-)
and salinity (haline) and is responsible for redistributing heat around the globe.
This change makes a lot of carbon dioxide (which is a gas that unfortunately makes the Earth warmer
and that we are emitting a lot nowadays) to be taken away from our planet’s atmosphere.
It reduces the global warming effect and can push the Earth into a new ice age.
This is actually exciting news because we have found evidence in rocks that shows
how the Southern Ocean and Antarctica play a big role in changing the Earth's climate.
--- Global Warming: The Ice Age's Misunderstood Cousin
Now, the natural thing would be for you to start thinking is: "But… shouldn’t global
warming cause us to melt, and not to freeze?" Ah, my dear, you are indeed correct. Global warming,
constantly caused by human activities, is indeed making the overall temperature of the Earth rise,
leading to the melting of ice caps and glaciers. It could trigger natural response mechanisms that
could potentially push the Earth into another ice age. For example,
more land gets exposed as the ice sheets melt. This land can then reflect less sunlight and
absorb more heat. This absorption of heat can lead to a reduction in global
temperatures.. and guess what? Contributing to the start of a new global glaciation.
So, while global warming and ice ages may seem like polar opposites (pun intended), they are
actually quite connected in a complex relationship of cause and effect. If you think about it. it’s
actually a nice reminder that even though human activities are currently driving global warming,
our actions can have unintended consequences that extend far beyond our initial understanding.
However, like every new theory, there are always some scientists that think the opposite. Those
ones believe that human-caused global warming may actually delay the onset of another ice age,
as rising levels of greenhouse gases in the atmosphere contribute to rising temperatures.
--- How Would We React?
The past pandemic showed us that humans have developed the ability to create an environment
that accepts what it’s going through and gets creative with it. I really wonder what our current
generation would do if it had to go through an Ice Age anytime soon and what creative thing sit
would come up with. So let’s leave science behind a little and have a little fun with this subject:
Firstly, I think that the world would very quickly look like a winter-ball on steroids.
Snow and ice would cover all cities, turning them into giant fantasy snow globes.
Cars would probably have to run on something other than wheels,
maybe something like skate and ice stoppers? Or is that too far-fetched. I mean we have to
adapt because it will be something that could last thousands of years. Will we have to start over?
Fashion trends would revolve around puffy coats and fur trimming everything. Ice fishing
would become the latest extreme sport, with competitors battling the icy depths to catch
the biggest frozen fish. Ice hockey would reach a new level of excitement as players would have
to constantly avoid falling icicles and slippery surfaces. I could keep going…
However, despite the challenges, people will adapt and find humor in the absurdity of their
frozen world. Ice Age-themed comedies and sitcoms would dominate the entertainment
industry. Laughter would become the ultimate defense against the cold,
and ultimately, laughing does make you sweat. We keep being reminded of humanity's resilience
and adaptability and how we would face the freezing temperatures with a mixture of
creativity, humor and lots of warm clothes. And who knows, we might even embrace the
icy conditions and adopt a new way of life. Scientists are still not sure when the next
ice age will occur. While global warming is currently disrupting the natural cycle of ice
ages, it is unclear how long it will take for the planet to reach a tipping point.
However, it is important to note that the current rate of global warming is unprecedented in Earth's
history. The rapid release of greenhouse gases, primarily by burning fossil fuels,
is causing temperatures to rise at an alarming rate. If we continue on this trajectory,
the consequences could be catastrophic. Therefore, it is imperative that we take
immediate action to mitigate the effects of global warming. Switching to renewable energy sources,
reducing greenhouse gas emissions and promoting sustainable practices are all essential steps to
protect the future of our planet. ---
In conclusion, the ice age is a fascinating geological phenomenon that brings both wonder
and challenges to our planet. From breathtaking icy landscapes to bone-chilling temperatures,
it's a rollercoaster ride of extremes. And while global warming may seem like its misunderstood
cousin, the truth is that our actions today could have unforeseen effects on the delicate balance
that keeps our planet in an ice age. So let's strive to understand and protect our planet's
geological intricacies, ensuring we don't tip the scales too far in one direction or the other.
Hey! This video ends here! Thank you so much for watching! What would you do if you had to
encounter an Ice Age? And what would you like to hear next? Let me know in the comments below! See
you on the channel! ---