AMNA NAWAZ: Scientists across the country are expressing alarm as the Trump administration dismantles another tool for understanding how the planet is changing.

Starting this month, more than 900 deep-sea ocean sensors will be pulled out of the Pacific and Atlantic Oceans off the coast of Washington, Oregon, Alaska, North Carolina, and Greenland.

Researchers say these are some of the most critical ocean observation tools we have.

William Brangham is here now to explain the latest.

William, what are these sensors and why do researchers tell you they are so important?

WILLIAM BRANGHAM: This was a decades-long, about $380 million research project, hundreds of sensors you described.

Some of them sat on the surface of the ocean.

Some of them went down hundreds of feet.

The way to think about this is like an ongoing medical checkup on the health of the oceans.

How salty is it?

How warm is it?

How do the currents move in the ocean?

Where are they moving?

How are the fish doing down there?

How is the ocean responding to climate change?

I think it's hard to overstate just how critical oceans are to life on Earth.

They regulate our weather.

They provide food for millions of people all over the world.

Over the last few decades, they have absorbed -- an enormous amount of the carbon pollution that we put up in the atmosphere has been taken up by the oceans, thus delaying some of the more negative consequences of climate change against us.

These sensors were looking at all of those things, and now we are in essence stopping that research project totally.

AMNA NAWAZ: So, if this is such an important project, what exactly is the Trump administration's rationale for dismantling it?

WILLIAM BRANGHAM: I wish I could give you a clear answer on this.

The National Science Foundation, which runs this, put out a statement justifying this that is incredibly hard to parse.

Let me just read this statement.

Here's what they said -- quote -- "The decision to de-scope aligns with NSF's wider strategy of a nimbler approach to prioritize support for evolving scientific priorities and emerging technologies, as well as smart life cycle management within its research infrastructure portfolio."

If you can parse what that actually means, you're a smarter woman than I. Meanwhile, the scientific community could not have been clearer about what they see going on here.

And that is another example, they argue, of the Trump administration turning off the ways in which we observe how the Earth is changing, specifically with relation to climate change.

One researcher I was in touch with today described this as an intentional choice to embrace ignorance.

I spoke earlier today with a researcher named Hilary Palevsky.

She's at Boston College.

She studies how CO2 moves from the atmosphere into the oceans.

And she described our scientific understanding like one of those tall Jenga towers of understanding.

And she said, this is one more example of pulling a tile out of that tower.

Here's how she put it.

HILARY PALEVSKY, Boston College: We don't know which piece of that Jenga tower is going to be really critical in seeing the changes that are coming in the future.

And so we really are at a time that we need more, rather than fewer, sensors out in the ocean.

And so this is really going in the wrong direction for what we need as a scientific community and a society.

AMNA NAWAZ: William, I understand this is a particularly fraught time right now to be cutting this kind of research into ocean monitoring.

Why?

WILLIAM BRANGHAM: It's because there are two enormously important phenomena happening in the oceans right now.

The first one is in the Pacific Ocean.

This is what is being called a Super El Nino.

This is characterized by incredibly warm ocean waters in the Pacific, which we are seeing right now.

A strong El Nino can affect weather patterns all over the world.

And this is now gearing up to be a potentially record-breaking El Nino.

That's one event in the Pacific.

Switching across to The Atlantic is a second system that goes by the acronym known as AMOC.

AMOC is this colossal conveyor belt that moves ocean currents all over the globe, particularly in the North Atlantic.

Some researchers have been detecting a signal that warming, particularly warming in the Arctic, could be disrupting AMOC and even overturning it.

And if that were to actually happen, this would be considered one of the most grave turning, tipping points that scientists fear could happen with regards to climate change.

If that were to happen, this would cast incredibly harsh winters over Europe.

It could send much more fierce hurricanes to the East Coast of the United States.

Most problematically, it could seriously distort the rain that feeds millions of people in Africa, in Asia, in South America.

And so the researchers that I had been in touch with are arguing, this is exactly the time that you do not want to be quite literally taking your eyes off the ocean.

AMNA NAWAZ: William Brangham, thank you so much for the very latest there.

WILLIAM BRANGHAM: Thank you.