- Polar Sea ice is one
of the most important insurance policies against
runaway climate change.
It helps regulate the earth's temperature,
influences global ocean circulation.
And it's critically important in protecting the ice sheets
from melting and causing massive sea level rise.
But as the world warmed,
something really confusing happen in the Southern Ocean,
while nearly all other ice on earth was decreasing
Antarctic sea ice levels were mysteriously increasing.
- It was a paradox, right?
We had a warming world,
but Southern Ocean sea ice was expanding
and that was in contradiction to what our models suggested.
- Unlike the steady downward trend of Arctic sea ice
Antarctic sea ice records since the late 1970s showed a
nearly flat line.
That's good news, right?
But then they dropped and they stayed low.
Reaching an all time record low in 2023 by a wide margin
And 2024 isn't looking so good either.
Scientists have been scrambling to figure out
what is going on
- This year.
Southern Ocean sea ice got
to just over seven standard deviations below the mean.
You would expect to see something like
that once every 700 billion years, which is just bonkers.
- The change has even been noticeable
to scientists working in Antarctica. There's
- Been a real lack of sea ice
around Antarctica. It's really alarming
- What they were seeing broke all
of their climate models and their
findings had them questioning.
If Antarctica is experiencing a state change,
- You don't need statistics
to tell you something different was happening this year,
and it was a big difference.
- And Arctic sea ice is critically important for the globe
as a whole, and some
of our most iconic species depend on it,
including emperor penguins.
The ancestors of this flightless bird roam the earth
millions of years ago during the age of the dinosaurs.
And they live through some pretty incredible
changes in climate.
But the threats they face today are unprecedented
and their future is precarious.
There are actually pretty good projections about
how their population will fare under different
warming scenarios.
So keep watching to find out what we can expect by the end
of the century and how emperor penguins may be a harbinger
for what's to come.
Antarctica has ice both on land in the form of ice sheets
and in the waters around it, in the form
of seasonal sea ice. Like in the Arctic,
the surface of the ocean
around Antarctica freezes over in the winter
and melts in the summer.
- At its summer minimum,
it covers an area about half the size of Australia.
And then in autumn winter this freezes
and it covers an area two
and a half times the size of Australia.
So we've got this huge area of sea ice.
This seasonal waxing and waning as there's more
and less sunlight, warmth over the southern
ocean is really reliable.
- But the stability
of the system was thrown into question in 2016 while
scientists were busy trying
to figure out why sea ice appeared to be increasing,
something shifted dramatically
- Then in in 2016, in our study, we find
that there's this abrupt decline in sea ice in a
space of two years.
The Antarctic lost as much sea ice
as the Arctic lost in three decades, right?
It's an really abrupt drop.
- That was a huge shock to the community.
We didn't see it coming.
- The following year showed signs of increasing,
but we're still consistently below average.
But then 2023 happened
- This summer was a record low.
The previous summer was a record low,
so we had two record low summers back to back.
And then this winter has been completely unlike anything
else we have seen in the records.
It's also unlike anything in the reconstructions.
We were missing an area of ice about two
and a half million square kilometers in size.
So that's an area the size of Alaska and Texas put together.
It's a vast, vast area of the ocean
that would normally be covered by ice that wasn't this year
And even though Antarctica feels incredibly far away when its
sea ice melts, it has cascading effects.
- Albedo means reflectivity.
So if we think about an ocean surface covered in sea ice,
the sea ice is white, and so it's highly reflective
and incoming sunlight is reflected from the
ice back to space.
And so it helps keep the surface of the earth cool.
And so this is one of the important roles
that sea ice plays in regulating global climate.
Another one is in influencing the deep ocean
circulation. Sea ice forms
when the surface of the ocean it freezes
and the ocean is salty.
Some of this salt is taken up into the sea
ice, but some of it isn't.
And this extra salty brine is actually
rejected from the bottom of the sea ice.
When the sea ice is freezing and this really dense heavy
water, it circulates around the shelf around Antarctica
and some of it sinks into the deep ocean
and it forms this, this deep ocean circulation,
- This deep overturning ocean circulation travels the entire
globe and takes over a thousand years to complete its cycle.
It's hugely important in the ocean's ability
to uptake carbon
and absorb the excess heat
that burning fossil fuels has created.
It slowing down has huge consequences
for our planet's climate.
- And finally, sea ice -
it physically protects the Antarctic coast
and the ice shelves, but when sea ice is absent, that waves,
they break on the ice shelves
and they can break up the ice shelves
faster than they other otherwise would.
Once we have these ice shelves collapsing, this means
that the Antarctic ice sheet, the ice
that sits on the continent, can slide into the oceans faster
and this will raise global sea levels.
- Scientists have estimated
that the Antarctic ice sheets hold enough ice
to raise sea levels by 58 meters if they were
to completely melt.
Fortunately, that's unlikely to happen anytime soon,
but West Antarctica alone could add over seven inches
of sea level rise by 2100. So
- Even though Antarctica is really far away,
and even we might not ever go there,
it can affect our global sea levels.
It can affect our global climate
- And it's home to some of our most iconic creatures,
including the emperor penguin.
- Emperors are such cool birds, you know, I mean they,
they, they are remarkable.
They are incredibly gregarious. They love each others company.
The individuals obviously realize that their chances
of partaking in reproductive activities is very limited.
You have to mate,
and you have to lay your egg at a certain time
because if you don't, you are missing out on
an entire breeding season.
- And emperor penguins lay just one egg.
The egg can't survive on the cold ice.
So the female very carefully transfers it to the male
who will incubate it for over two months, fasting
that entire time.
In addition to the time it took
to arrive at the colony and mate. These
birds do not build nests.
There is no nesting material.
They have to incubate their eggs on their feet.
That means that they cannot be on very steep
or very uneven ground.
- There are two main types of sea ice.
Pack ice is any type of sea ice that's floating,
not attached to land.
It can drift around and form large dense ice floes,
but it's a dynamic environment that's moving, breaking up
and shifting, which is not a good place to lay an egg.
Then there's the fast ice.
It's also sea ice that forms on the surface of the ocean,
but it's fastened to the shoreline.
It tends to be thicker up to two meters in the winter,
- And that is precisely where emperor penguins need to be.
- Once the egg hatches the mother returns from feeding at
sea. For the next five months, the mother
and father will take turns waddling up
to 100 kilometers over the sea ice to get food
for their chick in the open waters.
But if the sea ice
where the chicks are nesting disappears too soon,
the results can be catastrophic.
- We had this awful situation in November last year
where the sea ice that the emperor penguins were breeding on
actually melted away
before the penguin chicks were ready to swim.
This resulted in catastrophic breeding failure of
of four out of five
penguin colonies that are in a particular
region where sea ice was very low.
And what we know is that if sea ice keeps declining
the outlook for these emperor penguins, it's really bad.
- Emperor penguins have lived in this very, very dynamic and
and hostile environment for a long, long time.
These sort of events in general
probably happened in the past.
They, they have the ability,
as they have demonstrated several times in our days,
that they can shift location.
But what is so frustrating is
that it's happening more frequently
and it is happening to more colonies
and eventually they're just going to run out of options.
- These penguins only lay one egg a year.
So breeding failure year
after year has huge consequences for the population.
Studies have found that more than 90%
of emperor penguin colonies could face quasi extinction
by the end of the century.
But is all of this temporary?
We know that Antarctica is a dynamic environment
and it can be hard to see trends through all of the noise
Because the continent itself is in the way, sea ice
in Antarctica forms mostly at warmer latitudes,
meaning it's younger and thinner than Arctic sea ice.
It's distributed around the entire edge of the continent
and it's heavily influenced by wind, waves
and weather. Natural cycles mix with climate change
to really confuse the picture of what's happening.
So perhaps these eight years
of lower sea ice are just a blip
and the line will level out again.
- There is some evidence that sea ice does go
through these decadal cycles.
And so it could be that we're in this,
this natural cycle where sea ice is
low.
Scientists look back at those high sea ice years
to try to find clues.
- There was some hypotheses about,
maybe it's the melt water coming off the ice sheet
of Antarctica, and that fresh water sits on top
of the ocean, sort of seals off the heat in the deep ocean
from affecting the ice.
There was some theories about the ozone hole changing the
way the winds worked and the ocean transport.
- But I think the wide consensus is,
is the main contributor was the winds.
Sea ice is really affected by the wind and
wind changes were causing more sea ice to form.
- But that didn't seem
to explain the low sea ice years we're seeing. Now,
- The other thing that we know is that the ocean is warming.
The Southern Ocean is warming
because we are emitting greenhouse gases
and we are causing global warming.
And what we found is that whereas the atmosphere was really
important in driving sea ice in the high sea ice state,
we're now seeing a lot stronger influence
of the ocean in this low sea ice state.
And so, you know, it sounds pretty obvious to say that,
that the warm ocean is melting the sea ice,
but this wasn't always the case.
And I guess what this points to is
that now sea ice is being influenced in a different way
than it was previously.
- So is this the new normal?
- Something has so fundamentally changed in the climate
system that it's not just an aberration,
it's not just a a couple of years of strange anomalies.
This is the new state,
and that's what we expect to see for the future.
Or perhaps it's gonna change again
and we're gonna end up in an even newer lower
state of sea ice.
- 2023 shook our understanding
of climate change all around the world.
We collectively experienced heat waves, storms,
wildfires like never before.
And 2024 isn't shaping up to be much better
For emperor penguins,
there's a big difference
between the ambitious 1.5 degree goal,
the current trajectory of 2.6 degrees
and the unmitigated 4.3 degrees of warming.
Perhaps this state change towards a new level
of lower sea ice.
And the massive failure of penguin colonies will serve
as an alarm and motivation for humanity
to halt human caused warming
and to adapt to the inevitable changes ahead.
But what do you think?
Let us know in the comments below before you go.
Have you noticed all the great new shows here on Terra?
Animals, climate change, food science...
It's like a festival of science.
I specifically wanna talk about Fascinating Fails,
which tells the stories of how some
of science's biggest discoveries were actually
made by mistake.
You'll hear about everything from antibiotics to plastics
to the Big Bang.
There's a link in the description. We hope you check it out.
And if you do, let them know that Weathered sent you.