- 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 in 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.

- Antarctic 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've lived 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 a 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.

Its 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, the 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 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 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 mixed 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 looked 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 shed 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 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.

- 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.