Take a walk with me through
an ancient, verdant land: so vivid are the colours and
aroma of the entangled fauna, that it takes you an age to notice something
isn’t as it should be. It’s all quiet. The near absence of birds and mammals is
the only indication that this land is dying, its fate sealed by the ending of an
ice age — waters are rising. The lush landscape below your feet will soon be
30 m below the surface of the Pacific. Any species able to migrate have escaped to
continue their fight for survival in a warming, shrinking world. Those given life
by their roots, are held to perish by them. What is happening here? What we can
learn from the history recorded deep in the melting polar ice is of vital importance,
because right now, it is happening again. What is causing the ice caps to melt in
the present? How will it affect the most powerful climate systems on earth? And,
what hidden dangers does the ice contain? I’m Alex McColgan and you are watching
Astrum. Join me today as we look at what makes ice such an interesting
and crucial feature of our planet, and imagine a future, wetter Earth, one
whose existence may have already been forged. On Astrum, we love to explore gigantic
objects in our universe whose scale through time and space stretch almost beyond
our grasp. Look up towards Cassiopeia, and there is our closest Galaxy,
Andromeda. 2.5 million light years away, 200,000 light years from edge to edge. Yet,
despite its magnitude, we can connect to it. So it’s curious to me that looking only 80 years
to our future feels too distant to connect with; to understand that things we do today affect
tomorrow’s world. So, let me take you there. At the beginning of our journey is the
Ice. Ice is a remarkable substance, one that can store vast amounts of energy. As a
comparison, energy stored in modern electric cars, capable of accelerating tons of metal
to over 160 km per hour and carry both it and you hundreds of kms, could scarcely
melt ice that would fit on its back seats. The energy storage capacity of ice is a large part
of the reason that the climate has been so stable for the past 12,000 years [holocene]. The ice is
acting as a buffer against extreme temperature rises and falls. The holocene has been a unique
period in Earth’s history for another reason too — the rise of human civilisations. (Made
possible through the development of agriculture) The Antarctic ice cap first formed around 37
million years ago, the Arctic 2.7 million, as old as the light reaching us from
Andromeda, and both caps are important for our stable climate to this day. Their
historical size has largely been defined by Earth’s position and tilt in the solar system,
movements that affect the amount of energy that our planet receives. These movements are known
as Milankovich cycles, which I have covered in a previous video. According to these cycles the
ice at the poles should be increasing, we should be heading into an ice age, and sea levels
should be falling as the ice caps get deeper. But, instead, the polar ice is melting, massive
amounts of energy are being absorbed by the caps, and not only are we going in the opposite
direction that the Milankovich cycles predict — the ice loss is accelerating!
Should all the ice melt, we are facing a 70 m sea level rise, which will flood all
coastal cities on the planet. Fortunately, that degree of ice loss is exceptionally
unlikely. But we do need to know how much sea level rise to expect so that we
can plan ahead and protect Earth’s ecosystems. To predict just how much, we need
to understand why and how the ice is melting. We know the release of greenhouse gasses
is a driver of today’s global warming, overpowering the Milankovich cycles, causing the
ice caps to melt and the sea level to rise. But I was astonished to find out this hasn’t always
been the case! Detailed records kept in the Antarctic ice core reveal that in the past, it was
increasing temperatures that caused increasing CO2 levels. Cause and effect were flipped. But,
isn’t that a blatant contradiction?! Well, actually, no! Each positively influences the
other. It’s just a case of which happens first. We see this play out as the increased
temperatures of today’s climate thaw the permafrost around the Arctic circle,
releasing long-stored carbon reserves, which in turn accelerate further global warming. The mechanism by which increased
CO2 and temperature affect the polar regions reveals a complicated
and fascinating climate system. Greenhouse gases trap infrared (heat)
radiation emitted by the surface of the earth. This heat is retained by the
atmosphere (5.5 quadrillion tons) and the ocean (1.34 quintillion tons); around 90%
of the energy increase is absorbed by the ocean which is no surprise given it has
almost 250 times the atmosphere’s mass! So where does this extra energy go?
Well, as anyone who’s touched a hot stove or licked a ski lift chair knows,
heat moves from hot things to cold things, so it makes sense that it is at the cold
poles where we see many times the average global temperature increase - because that’s
where the temperature gradient demands that the energy flows. And it’s flowing there
primarily through the ocean currents. Because of its density and heat capacity,
water is very effective at transferring energy; that’s why water is used both as a coolant in
cars and a heating medium in homes. And why air, with a low density and low heat capacity, is
often used as an insulator. That difference allows you to sit comfortably in
a 90 ºC sauna for many minutes, while you’d reflexively be unable to insert past
your fingertip into water of the same temperature! Other factors play a role in melting the ice
too, like the albedo, or whiteness of the ice. Soot darkens the surface of the ice, causing
it to absorb more energy from the sun. Air quality measures are reducing particulates in
the atmosphere and on the ice, meaning we will see less melt from ice directly absorbing the
sun’s energy. But, the lowering of particulates in the atmosphere also blocks less sunlight
overall, so more energy reaches the surface, accelerating the greenhouse effect.
I told you it is complicated! Let’s explore the ways that the oceans are
melting the polar ice, as is happening right now on the West Antarctic Ice Shelf, a particularly
vulnerable area. It contains ice in several forms. Sea Ice is very seasonal, and is responsible
for the doubling of Antarctica’s area through winter. This ice melts through contact with the
ocean as ice cubes do in a cocktail. The direct impact of all the sea ice melting would only
contribute a few centimetres to sea level rise, but its importance lies in its role as a barrier
to the otherwise exposed ice shelf. The sea ice insulates the oceans from atmospheric warming,
and keeps the humidity and temperature of the air above it low. Being fresh and white, like the
most fairytale of glistening winter flurries, it also reflects a large proportion of sunlight
back into space. When this sea ice is low it exposes the Ice shelf which protrudes
almost all the way around the Antarctic. These floating ice shelves can be gigantic, some
- like the Ross and Ronne-Filchner shelves - are greater in area than my home country -
the United Kingdom. The warm sea water eats at the underside of the shelves; huge
icebergs the size of our biggest cities can break away as it weakens and drift as far as
Africa. Since these ice shelves are floating, they also contribute minimally to rising
sea levels. But it’s what the ice-shelves hold back that has the most potential for
sea level rise. As the shelves shrink, the main body of sheet ice that sits atop land
is more exposed allowing faster flow rates from Glaciers and ice streams. But don’t be
fooled, these ice streams are far bigger than their name would suggest! Incredibly,
some are as wide as the mouth of the Amazon, hundreds of kilometres long and kilometres deep
– all flowing towards the sea. Feeding these streams is the colossal ice sheet itself.
Since the ice sheet is supported on land, the mass of ice melt leads to
a direct increase in sea level. These ice-melting processes are natural
phenomena, and would still occur without global warming. The poles take fresh
snowfall and ice formation every year, which adds to the mass of the ice. And just
for them to remain at their current size, we would witness sea ice melting,
ice shelf calving and glacial flow. Though at this very moment, Earth’s polar ice
sheets are far from equilibrium: the rate at which they are losing ice is quicker than fresh
snow can fall, meaning that they are shrinking. Because of the extra energy in our oceans and
in the atmosphere captured by greenhouse gases, we are already committed to
significant ice sheet loss. Can we say how much sea levels will rise
from the melting alone? If you thought it would be a simple case of calculating the
volume of ice lost and adding it to the volume of water in the seas, well,
you can join me in being wrong! To arrive at an accurate estimate we need
to understand a few other interactions. We tend to think of Earth’s crust as solid, but given enough force the earth will
change shape too. As the ice melts, the continental plate that supports it bears less
weight and rises up above sea level, while at the equator the coastal land sinks into the sea,
creating localised sea level falls and rises. But the single biggest addition to sea level
rise to date required no additional water, and was simply due to the thermal expansion of what
was already there! Around half of the sea level rise we have already seen since the industrial
revolution has been due to this expansion. This process is easy to calculate, and we know how it
will contribute to sea level rise in the future. However, the deluge of cold, fresh water being
dumped into the salty sea has other, less predictable consequences. Remember, Earth’s
systems are dynamically intertwined. A feature of these dynamic systems is that they are
vulnerable to dramatic changes in behaviour, known as tipping points. As with playing
jenga, the tower becomes less and less stable as we mine the lower levels for
material to build ever higher. Eventually, merely touching the next brick brings it crashing
down. This would cause a very rapid phase change! One tipping point that could occur within our
lifetime is the slowing of the Atlantic meridional overturning circulation (AMOC). This is an oceanic
flow, a powerful energy transfer system. Should it weaken or collapse completely, sea levels on the
eastern seaboard of America could rise by up to 1 m, but in Europe, coastal waters would
recede. However, Europe would face other more extreme consequences. Around the world,
rainfall patterns would change drastically, pushing some ecosystems to become rainforests
while pushing others toward desertification. To understand how all of that is possible let's
look at how the AMOC functions now. The AMOC is part of the thermohaline circulation
system. It is driven by changes in heat (thermo) and salt concentration (haline).The
AMOC brings warm tropical waters up past the United States and across to Europe, helping
to make northern Europe warmer than it ought to be considering its proximity to the polar
circle! As these waters continue north to the Arctic it is partially frozen into sea ice,
which leaves cooler, saltier water to sink to the bottom of the ocean where it then
flows back south to complete the cycle. However, the melting of the Greenland ice
sheet is inundating the northern part of the AMOC with fresh water, diluting the
sea water making it less salty and less dense. This makes the gradient directing
the water to sink to become shallower, slowing down this part of the cycle and reducing
flow; just as a slow middle-lane driver on the motorway can cause a tailback stretching
frustratingly far back across all lanes. The slowing down of the AMOC backs up water
on the American east coast and reduces the flow to Europe meaning that sea levels would rise
further in America while Europe would be spared, though that’s little consolation to a
continent that will lose much of its way of life and food production capacity
through cooler temperatures. The UK alone is facing an average temperature drop of 10
ºC, which would make it colder than Iceland! The melting Greenland ice sheet also contains
organisms that we haven’t seen on Earth in hundreds of thousands of years. When a new
predator travels to a ecosystem not evolved to live with it, it can upset its delicate
balance. This is also true of a pathogen travelling through time. Most of the species
will be harmless, but as we saw in 2020, it only takes one ‘black swan’ to change everything.
With more cells being released from ice melt each year than there are grains of sand on earth,
the risk one is a black swan is significant. A risk that increases with the
depth of the permafrost thaw. The further back in time a potential pathogen is from, the bigger the jump in its genome and the
lower our ecosystem’s readiness for it. So, the world is changing. As we have seen, ice is an incredible
recorder of Earth’s history. Through studying its secrets, we can see
Earth’s past. Just as the ice cores detail Earth’s ecosystem as the Bering Strait flooded,
it contains our history too. As the Ice melts it replays many of humanity’s environmental
missteps by re-releasing trapped chemicals we have produced. CFCs stored in the ice can again
deplete the ozone, and accelerate arctic ice loss. Chlorinated pesticides, many long-banned from use,
can find their way back into Earth’s ecosystem; some of which will have been made even more potent
by their time stored in ice. Vaporised lead from the use of leaded petrol will also be re-released
as the ice layers that contain it melt away. This chemical cocktail adds yet more stress
to a global ecosystem moving ever closer to an invisible edge. When we add all these factors
together, 2100 could look very different. Exactly how different is under our control. The current
predicted average sea-level rise is 0.5 m. That doesn’t sound like much, does it. A map of the
world’s coastlines would look almost unchanged. Though, it’s not the averages but
the black swan events – the storms, the floods, the heatwaves – that drive
human behaviour. By 2100 a population the size of the US will be exposed to regular
coastal floods. Faced with increased risk, where will Earth's coastal populations move
to? How much will our way of life change? The rich diversity we see in cultures and
species on Earth is born out of adapting to the environment. Both humanity and life itself
have demonstrated time and time again that they are irrepressibly adaptive. Humanity can and has
to learn from its past and look to the future. So, there is hope. While the melting ice reminds us of the
environmental damage that we have been responsible for since the industrial revolution,
it also reminds us of how often we came together to make a change for the better when we understood
how we were affecting our planet and ourselves. I believe we can and need to do it again. It may well be that some engineering might be in
order in Earth’s future, to design and then build the technology that eases the pressures on our
planet’s ecosystems. Creating something that helps the planet might seem a tall order, something
only a brilliant inventor might accomplish, but have you considered that brilliant inventor
may just be you? “But Alex,” I hear some of you say, “I don’t have the technical skills
to accomplish something like that!” Well, maybe that’s true… but would you like them?
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