Alex Honnold Rappels The Moulin | Arctic Ascent with Alex Honnold | National Geographic

[Alex] Deep enough that it just turns black.
[Heidi] Yeah.
[Alex] Yeah, it's pretty far.
[Heidi] This huge hole is called a moulin. It acts like a drain, funneling meltwater to the base of the glacier. This is the abyss; it's all pretty big and pretty intimidating. This moulin should allow us to figure out what's happening beneath the glacier, so we're going to repel down into it.
[Heidi] Glaciers are rivers of ice. Normally, they flow slowly, pulled by gravity down towards the ocean. But the more water beneath the glacier, the faster it can move. It's pretty much like when you take an ice cube and you make it slide over a thin layer of water. It will slide so much faster. I want to find out if there's enough water underneath the glacier to make it speed up.
[Alex] I'm definitely more used to climbing up rock than down into ice. But this is a rare opportunity to help Heidi get the data that she needs.
[Heidi] Very few people have dared to enter into these holes. It's really one of the most dangerous environments on earth.
[Alex] Aldo Kane is here for safety and logistics, here to help the team make sure that we don't kill ourselves. Yeah, and then keep bringing it back out. We're trying to mesh frontline hardcore adventure with frontline hardcore science. You know, they go hand in hand. Honestly, he's just so striking and handsome. I just feel like he must be very capable. My wife looked him up on Instagram before the trip and was like, "Wow." You know, like, "Tell me about what it's like to be with Aldo." I was like, "Okay." Clean this section here and then run the ropes straight over that edge. Oh, that's not bad. That was a good toss.
[Aldo] When you're standing on top of the moulin, you can hear, "Crack! Crack!" It's like gunshots going off, and that's the ice moving. Watch out. Watch out.
[Alex] It just goes straight down for like, so far.
[Alex] Heidi has these little cylinders called piezometers. If we can drop them down to the bottom of the moulin, they'll tell us how much water is down there. The more water, the faster the glacier is moving and melting. I'm gonna go down a little bit.
[Alex] Okay, so is that the whole of it?
[Heidi] That was the whole thing, yeah.
[Alex] Yeah, perfect.
[Alex] It's very intimidating down there.
[Aldo] Yeah?
[Alex] No way!
[Alex] Let's see what we got, huh?
[Heidi] Mm-hmm. It has measured about a hundred kilopascals, which actually means that there was about 10 meters of water above it. 30 feet of water is a big pool at the bottom of a hole like that, isn't it?
[Heidi] Yeah, yeah.
[Heidi] This much water under the glacier can make it slide down the valley and melt faster at lower altitudes. Our results mean that this huge river of ice is now one more we need to keep tabs on.