Jane: This is But Why: A Podcast for Curious Kids. I'm Jane
Lindholm. On this show, we take questions from curious kids all
over the world, and we find cool people who can offer answers.
Today, I'm at Solheimejokull. That's a glacier in southern
Iceland. It's been around for 400 to 600 years. We're visiting
it to see what a glacier looks like. But you have sent us a lot
of glacier questions over the years, so we're going to go now
to the University of Iceland to talk with somebody who can
actually explain what they are.
Guðfinna Aðalgeirsdóttir: My name is Guðfinna
Aðalgeirsdóttir. It's a very long Icelandic name.
Jane: As you may have figured out by now, But Why went to
Iceland! That's an island country in the north Atlantic
Ocean, a little closer to Europe than it is to North America. One
of the things we wanted to learn more about while we were
visiting was glaciers. So after walking around, looking at an
amazing glacier called Solheimejokull, we went in
search of someone who could explain this geological
phenomenon to us. But to do that, we had to leave the
glacier go into the capital city of Reykjavik, where we walked to
the University of Iceland and into the bright and sunny
science building. That's where we found Guðfinna
Aðalgeirsdóttir in her office where she works as a professor
when she's not out walking around on glaciers herself.
Guðfinna Aðalgeirsdóttir: So I'm a glaciologist, and I became a
glaciologist because I'm really interested in skiing, and I
found this way of traveling on ice and snow as a job through my
interest and because I found this group of people who were
researching glaciers. So I didn't know that this existed
when I started, but I learned geophysics, so I was interested
in math and physics, and what I do now is I measure the
glaciers, I model them.
Jane: That might sound like she spends her days sculpting models
of glaciers out of air clay or something. But sadly, no. Or
maybe not sadly, because Guðfinna Aðalgeirsdóttir seems
to really like her job. What she means by modeling is that she
uses math and physics to create computer models for glaciers,
which are paired with climate models. Those models can help
researchers figure out what might happen to glaciers under
different conditions over the next many years. And of course,
as a professor, she also teaches students, and she does get to
ski.
Guðfinna Aðalgeirsdóttir: No, I ski a lot, so I take every
opportunity I have. For example, this spring, we were on
Mýrdalsjökull, and then we drive on the glacier, and then I had a
rope, and I could be towed behind the car in that trip. So
then I didn't have to sit in the car, but I was on the skis
behind the car, towed by a rope. And then we traveled to the
measurement location. And then when we gone and we did the
measurement, we drilled the thickness of the snow layer to
measure how much it was snowing during the wintertime, and then
I was towed to the next measuring place on the skis. And
then when everybody went home, I skied down the glacier. So that
was a great ski trip, but a measuring trip at the same time.
Jane: I have to just say, right now, it is not safe for you to
be towed behind a car on skis, unless this is something you're
specifically doing as an adult for your job in a very
controlled way. Do not try that at home.
Guðfinna Aðalgeirsdóttir: Well, that's true, yes. So we should
be very careful, and you have to train a lot to be able to do
this. Yes.
Jane: But wait, we're getting out over our skis. That's an
expression people use to mean "we're getting ahead of
ourselves and might fall over." We haven't really explained yet
what a glacier is. So let's do that now.
Eana: My name is Eana. I'm nine years old. I live in Victoria,
British Columbia, and my favorite season is winter,
because it's close to my birthday, and I love snow. And
my question is, how are glaciers formed?
Kira: My name is Kira. I live in Barrie, Ontario. I am six years
old. How do glaciers get there in the first place?
Jane: What is a glacier?
Guðfinna Aðalgeirsdóttir: That's a good question. So glacier is
ice, and the ice is formed because the precipitation of
last winter didn't melt in the following summer. So that means
that there was a positive mass balance there. This region
gained and when there is a sequence of year where there is
snow left in the autumn, buried then under next winter snow
layer, then that accumulated snow is compacted. And when once
that has become densified, so that the snow that was like
fluffy and flurry in the beginning is compacted into
glacier ice, then it can start to flow. And the flowing happens
because the thickness of the ice is high enough or large enough.
So once the thickness is large enough that the ice can start
deforming under its own weight. And you can think of this as
honey. If you put a honey on the table, and it may be, may be
like a pile, and the pile then kind of floods out because the
thickness is too high for the surface tension, if you like.
Jane: So a glacier is snow that forms on top of land and gets
squished down year after year as more snow falls, and not all of
it melts. Over time, that snow pack gets so heavy and compacted
that it turns to ice, and then that ice starts to move under
the force of its own weight. That is a glacier. And one of
the most important things is that glaciers aren't really
glaciers until they start to move.
Guðfinna Aðalgeirsdóttir: You can have snow packs that are
just sitting there, but as soon as the thickness of that ice is
large enough that the weight of that ice column is really
pushing it to flow and deform under its own weight. And
specifically, if the slope underneath, so the bedrock
underneath is maybe steep, then the glacier can start flowing
downhill, and then it has become a glacier. So it's ice that
flows, and then you have a glacier.
Jane: And glaciers can only form on land, right? We're not
talking about icebergs.
Guðfinna Aðalgeirsdóttir: Well, some icebergs are carved off
glaciers, so they are formed on a glacier. And there are many
icebergs. For example, the Titanic, the iceberg that caused
the Titanic to sink was breaking off Greenland ice sheet. That's
another thing that I find interesting, the glacier ice
flowing off and breaking off in the fjords, for example, in
Greenland, that's the oldest ice, because that has been
formed somewhere way up and has been transported down to the
axis of the glacier and is breaking off.
Jane: So it's almost like a conveyor belt where the new snow
gets buried and goes down and down and down, and then
eventually it comes out at the snout, and that's the older ice.
And that newer snow is pushing down from the top and sort of
pushing that older ice continually downwards or
outwards. How old are glaciers?
Guðfinna Aðalgeirsdóttir: That's very dependent on the location,
like we're in the world, but also we're on the glacier, like
we were saying, the conveyor belt. So the youngest ice is on
the top in the accumulation area, and then the oldest is at
the snout. And the glacier ice in Iceland is probably up to
800, 900 years old. So that's the time that it takes for the
ice to be transported with a conveyor belt that the ice
itself down towards the axis. There are places that are much
older, much, much older. The Greenland ice sheet and the
Antarctic ice sheet. They are much bigger. There are, like
whole continents covered with ice, and the ice in Greenland,
it's about 130,000 years old, and they have found around 1
million year old ice in Antarctica.
Jane: Ice that is a million years old? Imagine putting that
in your glass of water. Just kidding. Scientists do collect
some of that ice, but they don't just let it melt in a glass.
Professor Aðalgeirsdóttir says that ice is like a time capsule.
It contains a record of the precipitation, the snow and rain
that fell a million years ago, and the bubbles trapped inside
the ice are a time capsule telling us about the air a
million years ago, so we can learn a lot about the past from
glaciers.
Coco: Hello. My name is Coco. I'm eight years old. I'm from
St. George, Utah, and my question is: how does algae get
into glaciers and turn them pink?
Guðfinna Aðalgeirsdóttir: Yes, this is a very interesting
question, and the surface of the glacier can't be variable. And
the question about the algae, I don't actually know, but I
think, and that's my wild guess, now. I think that algae are
blown onto the glacier and start growing, and then they can,
well, you can think, well, what can grow on a surface that is
freezing at the freezing point, even, and very cold, and there
is no soil to grow. But apparently those algae quite
like the cold surface, and there may be the solar radiation give
them enough energy to grow, and that causes kind of like a
reddish hue.
Jane: We checked on this, and the color is coming from algae.
The algae itself is green, but it has a secondary red pigment
called a carotenoid. In the summer, the algae can turn on
their red pigments as a protective barrier against UV
radiation from the sun. It's kind of like sunscreen. But this
red color causes the algae to absorb heat instead of
reflecting it, and that leads to glaciers that melt faster than
white ones. Pink isn't the only color you can see in a glacier.
Sometimes a glacier looks blue. The more dense the ice, meaning
it has fewer air bubbles and is packed down under its own
weight, the more likely it is to look blue. Those large, dense
ice crystals are absorbing some wavelengths of light and
scattering the blue light back to your eyes so it looks blue.
Generally speaking, the older the glacier ice, the more likely
it is to appear blue. But glaciers can be other colors,
too. They can be white, blue, pink, brown, black and more.
Guðfinna Aðalgeirsdóttir: In Iceland, that color changes can
be because dust is blown. It's very windy in Iceland and in the
highlands is basically a desert. And our sand, because it's a
volcanic island, our sand is very black. So the black sand is
blown onto the glacier, and that causes like a dark, darkening of
the surface. There can be even sand dust from Sahara on, some
places in the Alps, and that sand is kind of yellowish and,
and then the algae contains the surface color. And anything that
is blown onto the glacier will have an effect.
Jane: The darker the surface of the glacier, the faster it
melts. Speaking of which, when we come back, we'll talk a
little bit about how increasing global temperatures are
affecting glaciers around the world. And did you know you can
find glaciers in the tropics?
This is But Why: A Podcast for Curious Kids. I'm Jane Lindholm.
We're learning about glaciers with scientist and professor,
Guðfinna Aðalgeirsdóttir, a professor and glaciologist at
the University of Iceland. Remember at the beginning of
this episode, when I said I was standing at a glacier? You can
see glaciers from a lot of Iceland. Even though only about
10% of the country is covered by ice, these glaciers are a very
striking feature of the landscape, and some of the
glaciers are pretty easy to walk right up to and touch, like the
one we visited. I asked Professor Aðalgeirsdóttir to
tell us about the glacier we had visited before we went to her
office. It's called Solheimejokull. It looks like a
big pile of dirty black ice and snow tumbling down in between
two valleys and piling up on itself. It actually starts
higher up in the Icelandic Highlands as part of a much
larger glacier, an ice cap called Mýrdalsjökull. That ice
cap is on flatter land and kind of spreads out in all
directions. And Solheimajokull is an outlet glacier, where the
ice is heading downwards toward the sea.
Guðfinna Aðalgeirsdóttir: So Solheimajokull is flowing
towards south, towards the coast in Iceland. And this outlet
glacier is like a long tongue, and it's bending a little bit
down into this valley, and the end of it is now in a lake, and
the lake formed only maybe 15, 20 years ago. I'm not exactly
the same the exact date of it. And that lake is forming because
the glacier is getting shorter. And the glacier is a little bit
like a conveyor belt, and it's transporting the snow
accumulated on the big ice cap, Mýrdalsjökull, down into the
lower region. And the glacier is also like your bank account, a
little bit, that you put something in, in it in the
wintertime. So the snow comes in the winter time and that certain
amount, and we go and measure that in the springtime, how much
was coming into the glacier. And then during the summertime, at
the lower region, and but also high up, is ablation. So
ablation is how much is melting, and the ablation is then also a
certain amount. And then come the bank account that you can
say that mass balance of the glacier, if you take more out
than you put in, the glacier is going to get shorter.
Jane: And solheimajokull has been shrinking recently.
Guðfinna Aðalgeirsdóttir: Yes, since 1995, so now 30 years,
it's getting shorter, sometimes 50, up to 100 meters a year. And
we know this because we go and measure every year the position
of the snout. So we call it the snout where the glacier ends,
and the snout is now in the lake. So it's not only melting
on the surface, at the snout, but it's also breaking off into
the lake. So then that's called calving, because it's kind of
like calf being broken off the of the snout of the glacier. So
so the ablation possibilities are breaking off into the lake
and melting at the surface, because the high temperature.
Jane: given how cold it needs to be for a glacier to form, you
might be surprised to learn you can actually find glaciers in a
lot of places on earth. You can even have a glacier in the
tropics or near the equator, but you need to have more snow that
falls than the snow that melts year after year after year. So
for that to happen in really warm parts of the world, you
usually need to go up. If there are very tall mountains where
the air is cold, even if it's tropical, down below, you might
be able to find a glacier.
Guðfinna Aðalgeirsdóttir: In Africa. There is the Mount
Kilimanjaro, and we find a glacier there that is actually
shrinking quite fast at the moment. But in the tropics, if
you get high enough, you can find glaciers.
Chet: My name is Chet. I'm five years old. Ontario, Canada, and
my question is: why glaciers are formed, and they shape the land?
Jane: Sometimes, where we live in North America, people will
talk about the landscape and say, "Oh, that was formed in the
last ice age when the glaciers receded." And here in Iceland,
we often hear, "this is a landscape that has been shaped
by volcanoes and glaciers." How do glaciers shape a landscape?
Guðfinna Aðalgeirsdóttir: They are really like bulldozers. So
in areas where there is sand underneath a glacier, they're
basically just shoveling the sand like bulldozer in front of
them, and they create what we call frontal moraines. And those
moraines are then like marking of a bulldozer that has pushed
the material in front of it. They also carve the valley. So
valley is V-shaped, kind of like a V if there is only a river at
the bottom that is carving the landscape, but if a glacier then
starts to fill that valley, then it carves and create, kind of
more like U-shape, and it kind of grinds the bedrock underneath
it and transport it. Remember, it's a conveyor belt, so it
transports the rocks that they grounded from the sides. And
then we can see that V-shaped valley haven't seen the glacier,
but the U-shaped valley, those are the valleys that the glacier
has formed.
Jane: And if we think of it as that bulldozer and it's pushing
that material forward, then sometimes it also leaves that
material there, and does that form new hills or mountains?
Because, again, we're thinking of like a bulldozer for a giant,
not a bulldozer that any of us could drive so you could see a
hill or a mountain that was sort of left behind, like pushed over
there, and then just discarded by the glacier?
Guðfinna Aðalgeirsdóttir: Exactly. And this is how we know how big
the Laurentide ice sheet was in North America. And the
Scandinavian ice sheet, how big they were, because we see those
land forms that exactly those bulldozed hills that are then
the leftovers off that big bulldozer that is now gone.
Jane: I think that's kind of amazing to think about someone
like you can go walk outside and see into the past, because you
know how this landscape was formed. And I wonder if in your
head, you can almost picture what it might have looked like
1,000 years ago, or 10,000 years ago.
Guðfinna Aðalgeirsdóttir: Yes, and even shorter distances,
because we see, for example, in Solheimejokull, where you were,
we can see now how big the glacier was because the
vegetation hasn't come yet. So in areas where the glacier has
recently been removed or retreated from, there are not
vegetation yet, but in areas that have been uncovered or
released from the glacier longer time ago, we see that there is
moss and maybe some grass visible. So the landscape is
really telling us how big the glaciers were and how extensive
they were, and that's what we are using to read the landscape
and of course, the climate tells us that we understand this
relationship, that if you get cooler climate, the glacier can
grow, and when it gets warmer, the glacier can shrink.
Jane: And shrinking is What many glaciers are doing right now.
Glaciers are always changing, growing and shrinking over time.
But right now, they're shrinking all over the world, and at a
fast rate, because our climate is getting warmer. Some glaciers
are even disappearing. But if glaciers have gotten bigger and
smaller, appeared and disappeared over the whole long
history of the earth, why do researchers like Professor
Aðalgeirsdóttir think that what's happening to glaciers now
is a problem and not just part of a normal cycle?
Guðfinna Aðalgeirsdóttir: They grow and shrink as a response to
temperature changes and precipitation changes, and they
are very sensitive, actually. But what they also are, they
have a long memory, so they are kind of integrating their
climate over long periods, and their response is telling us how
the climate has been changing. And we see records from
different regions in the world, and and more and more
information from the ice cores, from the big ice sheets,
indicate and sort of confirm this idea of ice ages and and
interglacial periods, so those warmer periods in between, and
those are natural, and those are kind of because of the distance
of the earth to the sun is changing, and that is causing
the ice ages to form. Also the tilt of the earth axis and the
wobbling speed is also changing, and that combination causes the
ice ages and the warmer periods. And those are happening on long
time scales, like 40,000 years and 100,000 years time scales.
So now, if we think of those timescales, like 100,000 years,
and compared to the time since we started burning fossil fuels,
that's only 150 years ago, and also building up that amount of
fossil fuel that we are burning out that takes millions of
years, like the reservoirs that we are using now for our energy
consumptions have been formed over millions of years. And in
the span of 150 years, and I say 150 because often, often we talk
about 1850 as the beginning of the Industrial Revolution, and
when we started having, like fuel engines, and started
burning coal for heating our houses and and fuel and gas. And
of course, there's a lot of technical evolution, really
rapid evolution of technology, and we managed to start flying
between the continents and using a lot of energy. And in that
period, we have emitted by burning the fossil fuels, the
CO2 in the atmosphere, and that is causing the temperature at
the surface to warm up. And now what has been natural and maybe
variable over the different regions in on the surface of
Earth, we are now seeing very clear signals. All the glaciers
in the world are responding. We have already warmed the planet
on average, 1.1 degree. And all the glaciers are telling us that
they can feel that. So the clear signal everywhere, from
Patagonia to Svalbard Icelandic glaciers, the Himalayan
glaciers, and, of course, the big ice sheets in Greenland and
Antarctica, they are starting to shrink. So let's just make that
thought experiment and say the temperature rise stopped at 1.1
degree, the glaciers, and it depends on how... size or the
bit how big the glaciers are, they will take few decades to
adjust. So the conveyor belt has to kind of figure out what the
new size should be, and then they would be about 40% smaller,
or the amount of the volume, amount of current glacier will
be about 40%. If we continue to warm, the more of this ice will
be lost. So the message from the glaciers is really stop the
warming as fast and as soon as possible and as much as
possible.
Jane: There have been agreements made among many countries to
limit greenhouse emissions, the gasses we put into the
atmosphere that are contributing to a warming climate. Countries
have worked to reduce emissions so we can limit that average
climate warming to two degrees. But those agreements don't seem
to be making a difference so far, and countries sometimes
change their mind about what they're willing to do, depending
on who's the president or prime minister or political leader at
any given time. Sometimes, countries or governments even
decide they no longer want to be part of the agreements, like the
United States did at the beginning of 2025 with something
called the Paris Climate Agreement. Pretty much every
scientist agrees climate change is happening at an alarming
rate, and it's going to affect all of us. But governments
disagree about what to do. Professor Aðalgeirsdóttir says
she thinks all countries are going to have to deal with it
one way or another, whether we like it or not, and the ways we
change our policies could wind up happening very quickly as the
climate forces us to think differently.
Guðfinna Aðalgeirsdóttir: Many places are using renewable
energy, and they're called renewable energy because they
are not using their fossil fuels, their coal and oil and
the gas that are burning and emitting CO2 in the atmosphere,
and replacing it with solar energy or wind energy and and I
think we could use tidal energy as well. There are a lot of
energy sources, geothermal, and there are energy sources that we
know how to harness, and we know that they're not emitting CO2,
but it's kind of like comfortable to still use and it
all the systems are built on the fossil fuels. But I think the
decision, once we make the decision to say, "Okay, we
really need to swap," I think that will happen fast. We are on
the verge of transition, and this is why we are talking about
the transition. We really need to move into this renewable
energy regime, because we understand that the regime that
we have had in the last 150 years is both not good for the
climate and it's also not sustainable, because we're going
to run out of those fossil fuels anyway.
Jane: And glaciers are helping us understand the urgency needed
to move in a new direction. That's it for this episode.
Thanks so much to Professor Guðfinna Aðalgeirsdóttir at the
University of Iceland for talking about glaciers with us.
As always, if you have a question about anything, have an
adult record you asking it on a smartphone using an app like
voice memos, then have your adult email the file to
questions@butwhykids.org. But Why is produced by Melody
Bodette, Sarah Baik and me, Jane Lindholm at Vermont Public and
distributed by PRX. Our video producer is Joey Palumbo, and
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