EOFF BENNETT: Well, if you have been following Miles O'Brien's reports from Antarctica on our broadcast and online, you know he's reporting on an international group of researchers trying to measure what's happening to one of the fastest melting glaciers there.

And their work is trying to capture information in ways that have never been done before.

Tonight, he has an update on how all that turned out, part of our periodic series Tipping Point.

MILES O'BRIEN: At long last, they got to the core of this far-flung mission.

Hot water was sluicing through glacier ice like a knife through butter, a milestone moment at the most menacing glacier of all, Thwaites.

It was a long, strange journey to get to this place and time, 11 days on a Korean icebreaker from New Zealand to West Antarctica, 10 days waiting for the clouds to lift so the helicopters could too, and 10 more setting up camp on the vast void in the teeth of harsh Antarctic winds.

MAN: Finally.

(LAUGHTER) MILES O'BRIEN: Researchers at the Korea Polar Research Institute, KOPRI, partnered with the British Antarctic Survey, BAS.

They wrote the book on this blitzkrieg boring method.

Pete Davis is a physical oceanographer.

PETER DAVIS, British Antarctic Survey: We shovel for days and then the wind -- the wind was too strong.

We had to delay.

It partly is uncomfortable for us, but also the windchill factor.

It just makes everything freeze, and freezing, as we say, our worst enemy.

MILES O'BRIEN: This glacier is large enough to raise global sea levels 2.5 feet.

It is a river of ice flowing at a rate of 30 feet per day, ripping apart into chaotic rifts strewn with ice boulders, melting tens of times faster than its neighbors.

And this is the perfect spot to figure out why.

It's on the grounding line where the glacier, the land and the Amundsen Sea meet 3,000 feet below.

It was a little after 4:00 p.m.

January 30 when they broke through the bottom of the ice.

As they reeled in the hot water hose, Pete Davis showed me a mother lode of scientific instruments ready for dunking, devices that measure salinity, temperature, depth, current and dissolved oxygen.

PETER DAVIS: This is the take-up data.

If we get this down to the bottom of the ocean, even if we don't recover it, we have a profile.

And that is 100 percent more data than we've ever had from here before.

MILES O'BRIEN: On the other side of the tent, the mooring instruments designed to gather all those readings continuously for perhaps a year, transmitting the data in near real time.

PETER DAVIS: What we're trying to study here, more to do with kind of processes and the process of melting.

A year is more than enough to see the processes in action and to get the understanding that we want.

MILES O'BRIEN: As Friday slipped into Saturday in this place of no sunsets, the temperature dropped, measured invisible breath and what looked like an invisible driller, his gloves warming up on a hot hose.

The team gave the sensors a warm bath and sent them down.

They got five profiles of the water below, a successful warmup act for the main event, the mooring that would stay behind.

Down it went.

But around 1:30 p.m.

on January 31, there was trouble below.

Pete Davis logged into the mooring instruments.

It looked good at first, but then he realized they all had identical temperature readings.

PETER DAVIS: OK, I'm pretty sure we're stuck.

I think we are stuck at about 650 decibars.

I'll come down and discuss options.

MAN: Thank you.

MILES O'BRIEN: They pulled a little bit, but everyone here knew they'd lose this tug of war.

Remember, freezing is their worst enemy.

When super cold glacier ice grabs an instrument, there is no plan B. KEITH MAKINSON, British Antarctic Survey: If you linger at any one location with equipment, it could freeze to the side.

And, unfortunately, something along those lines happened.

MILES O'BRIEN: Keith Makinson is a 37-year BAS veteran.

The instruments are frozen solid 2,300 feet below the surface, 650 feet from the bottom of the ice.

The exhausted tight-knit team tried to console each other, but there's a deep well of sadness.

KEITH MAKINSON: The whole team has worked really hard for many years.

It's a really hard blow.

MILES O'BRIEN: And yet they did not walk away empty handed.

They have a snapshot of data from a place where none existed before.

And it's not a pretty picture.

The water temperature here is nearly 34 degrees, 5.5 degrees warmer than the freezing point of glacier ice in seawater.

There's no question why the glacier is melting.

But the forecast they hoped to give the world remains elusive.

Antarctica does not give up its secrets easily.

But the people who come here to unlock them won't give up either.

For the "PBS News Hour," I'm Miles O'Brien at the Thwaites Glacier.