Go far enough and it gets dark in the middle of the day.

This is what the brief winter daylight looks like in northern Norway.

That's where I meet up with a team of researchers bound for the Arctic Ocean.

I'm Eli Kintisch and I'm spending two weeks with scientists

exploring the Arctic during the polar night.

The time of year that brings 24-hour darkness.

We're here in the dark to study the Arctic ecosystem before

the ice that defines it disappears.

Seasons are supercharged in the Arctic.

As the Earth orbits the Sun,

the amount of light reaching the northern hemisphere changes.

You may have noticed your days shrinking in the winter,

but it's way more drastic near the North Pole.

Where for four months the Sun never rises above the horizon,

and then in the summer, the Sun never sets.

The sea ice floating on the Arctic Ocean

follows a similar pattern.

Growing in the fall and winter and melting in the spring

when the massive spring blooms of algae feed the ecosystem.

But alongside those drastic seasons,

scientists have also detected a long-term trend that's underway.

Back here on earth, new word that the Arctic sea ice

has melted to near record levels.

Global warming will leave the Arctic ice free

during the summer within two decades.

Look at where the sea ice was in the 1980s

compared to the first decade of the 2000s.

And this line shows the data from 2018 so far.

Twenty years ago, the part of the sea we explored on the Helmer Hanssen

would have been coated with ice three to six feet thick.

We visit 22 stations on our journey

collecting measurements and samples

to gauge the health of the ecosystem

before the light returns in the spring.

Scientists have mostly ignored the Arctic winter

assuming that life here is dormant during the dark months.

But when they looked closer, they found an ecosystem teeming with life.

The mission of this journey is to track the physical and biological

aspects of the ocean as the ice vanishes above it.

Water samples from the deep helped scientists

identify currents that may be changing.

Robotic gliders roam the sea for months

measuring the properties of water

and probing for signs of life.

You've probably heard that big arctic species like

polar bears are endangered by the melting ice,

but tiny creatures also rely on it.

Some types of algae cling to its surface

and when they die, they fall to the muddy sea floor

becoming food for mollusks, worms, and crustaceans

and those creatures are food for fish, seals, and ...

walruses.

Stir crazy scientists really like walruses.

Other scientists zap the water with light to

detect algae cells and measure their response.

Animals called zooplankton just a few millimeters long

come up in the nets.

And the scientists test how they behave

under different light and water conditions.

They also document which species are present

and how many. As do the team's studying fish.

Without this data we won't be able to measure

how less ice and more light will change the ecosystem.

Shrinking sea ice means more light reaches

the Arctic Ocean in the spring and fall.

And that light is fueling massive new

blooms of algae called phytoplankton.

That's already helping several species of whales

thrive in the Arctic.

But will the extra light benefit the entire ecosystem in the future?

It depends.

These nutrients like nitrogen and phosphate

are found naturally in the ocean.

They nourish the algae like fertilizer for a garden.

But we don't know whether their levels will rise

along with all the new sunlight.

As the light floods in a separate problem is disruptions in timing.

The blooms are coming earlier in the spring on average.

But if they appear too early baby zooplankton that

hatch later could go hungry. And fish populations in turn

would diminish as well.

The Arctic has undergone massive changes before.

But carbon pollution is causing Arctic

summer temperatures to rise faster than they have in 1,500 years.

It is too soon to know how severe these disruptions

will be on the ecosystem.

So scientists will return to the same stations in the spring and early summer

to monitor a rapidly changing landscape.

Thanks for watching Thaw.

The next episode in this three-part series

we'll look at how the Arctic could be affecting

weather across the world.