Whether you observe from the sea or from the air, there's less Antarctica to see every year — less ice on the land-bound ice cap and glaciers and more ice breaking up and flowing off onto the oceans.

Captain Oliver Kruess pilots his cruise ship — the National Geographic Explorer — through the flows. Antarctic adventure tourism has become big business. But he says something happens to the people who come down here.

"Initially, many of them come for the seals, for the penguins, for the whales," Kruess told CBS News senior foreign correspondent Mark Phillips in a report for "Down to Earth" by CBS News on Facebook Watch. "But when they return to Antarctica, they come for the ice — the shape of the icebergs, the sea-ice set up, the ship in the ice."

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"So much of the earth's fresh water is sequestered here in Antarctica in that huge ice mass that's frozen there," NASA scientist John Sonntag said. "A good way to think of both Greenland and Antarctica is as a gigantic mountain of ice. They're not just thin layers of ice and rock, they're gigantic mountains of ice, two to three miles thick so that's a lot of sea level that's locked up in these ice sheets."

Scientists on NASA's ice-survey flights have confirmed that more ice melts into the sea each year than gets added back to the ice cap through snowfall.

"There are several spots around here, around Antarctica, that are believed to be in this irreversible situation, where the ice on the ground is going to flow into the sea and there's nothing we can do to stop it at this point," said Ken Taylor, an ice scientist who has been studying the changes in Antarctica for years.

The consequence is "inevitable sea level rise," Taylor said. "There's at least three feet already locked in down here in Antarctica."

Also inevitable is the threat to low-lying coastal areas around the world that the sea-level rise will cause. It may take decades for that to happen, but it will happen. The more the darker sea-water is exposed, the faster the sunlight warms it, the faster the adjoining ice melts.

In the meantime, NASA's program of ice measuring flights is coming to an end. A new satellite will take over a lot of the scientific work. But further investment is in doubt because the United States' chief executive remains a climate change skeptic.

"What about the scientists who say it's worse than ever?" Lesley Stahl asked President Donald Trump on the Oct. 14, 2018, edition of CBS News' "60 Minutes."

"You have to show me the scientists because they have a very big political agenda," he responded.

"You know, we're not politicians here, we're not policy people, we're just engineers and scientists. I don't know anything about politics, but I do know how to measure changing ice," Sonntag said. "People can't hide from facts forever, and I think the American people understand that."

It can take a trip down here to immerse yourself in the realities of climate change.

"It is, for some people, a controversial discussion, what we have. But here, of course, we have it — it's all around us and I think you can do it without having a political thing behind it," said Kruess. "You're just looking, really, at facts, and you are discussing those."

Kruess believes it's important for the people who come here to see what they see and to take back the message.

"We believe that we are producing ambassadors," he said.

Even among the tourists who come down here, like Lori Fey, there is pause for thought.

"It gives us a broader perspective and a deeper understanding of what the science actually is in an apolitical environment so that each of us can go back and go, well you know you might want to look a little deeper, here's some really interesting facts that I recently learned," Fey said.

"My hope is that the science prevails and I think it will, because in the long path of human history, it always has," said Sonntag.