From the Center for Investigative Reporting in PRX, this is Reveal.

I'm Alexan, and today we are going to the ends of the Earth to report on climate change.

We begin in Antarctica.

That's the sound of penguins nearby Thweights Glacier.

Thweights is a huge glacier.

More than a half a mile thick and the size of Great Britain.

And it's no surprise, it's melting.

Many scientists are predicting that Thweights may be doomed to crumble into the ocean.

If that happens, global sea levels could rise up to two feet just from this one glacier.

But that's not even the bad news, because this glacier is holding back another colossal sheet of ice.

Kind of like a cork in a wine bottle.

If all of it slips into the ocean, sea levels could rise by 11 feet.

Few people have ever stepped on Thweights Glacier, and no one has ever traveled by sea along the glacier's front until now.

A group of scientists spent two months aboard a research vessel to study Thweights up close.

Reporter Carolyn Beeler from the public radio show The World joined them in this first of its kind expedition.

My journey starts on a windy day at the end of January, at a port near the southern tip of Chile.

I walk across a gangplank to board an icebreaker at the length of a football field.

With nearly 60 scientists, staff and crew.

Just walked on the ship.

I knew home for eight weeks.

In port, the Nathaniel B. Palmer feels solid and stable, like a floating college dorm with a cafeteria and bright green flooring.

But as we sail south from Chile and through open ocean, 20-foot swells toss it around like it's a little dinghy.

...