Denali's Ruth Gorge could be deepest in North America (if it weren't filled with ice)

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An aerial view of the Ruth Glacier in Denali National Park and Preserve (Martin Truffer)

Denali National Park’s famously beautiful Ruth Gorge might be the deepest such chasm in North America.

That is, it would be if it weren’t filled with ice.

To get its depth, researchers had to measure just how much ice is in the gorge, using snowmachines to drag long radar antennas across the glacier’s surface.

In a study featured recently in the New York Times, they now say they have an answer.

University of Alaska Fairbanks glaciologist Martin Truffer says their method for determining the true depth of Ruth Gorge could also help our understanding of how much ice is held in other mountain glaciers, which are changing faster than other types of glaciers in a warming climate.

But to get the measurements in the first place, Truffer says they had to fly in to one of the most visually stunning places on Earth.

Listen:

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This interview has been lightly edited for length and clarity.

Martin Truffer: It’s very spectacular, you know, with Denali at the end there. And then as you head in, you have Moose’s Tooth on one side, which very big mountain with just very steep walls. You’re really flying into this just enormous gorge. And that then opens up up-glacier into this area called the Amphitheater, and it’s just very, very stunning, even if you’ve seen lots of mountains, this is a scale that’s kind of blows your mind.

Casey Grove: Tell me more about the idea of just trying to figure out how deep the ice is. I mean, how complicated is that to figure out?

MT: So, in some ways, it sounds really easy. What you do is you use a radar, because that ice is quite transparent to radar waves. But the problem is that these radar systems, there is no way to really direct the energy. You make really long wavelengths, so you have these really long antennas. In the case of the Ruth, we use, like, 100-meter-long antennas. So these are is pretty massive. And when you have that, you can’t really direct the energy, it just goes everywhere, and then you collect whatever comes back, and you hope that you see the signal from the bottom. But if you’re in geometries like the Ruth Gorge, you get reflections from these steep sidewalls, and that clutters the signal very much.

So we didn’t get the measurements in the gorge itself. But then there’s sort of pretty simple models you can do where you essentially take the glacier depths you have at the entrance of the gorge, and that’s where it worked well, so we know how deep it is there, we can measure how fast the ice flows there. So from that, we can say something about how much ice is actually going through a cross section as it enters the gorge. And then if you know how fast it is down in the gorge, you can figure out from that how deep it must be. And then you have an end point that you want to hit. You want to see whether you still get the right answer at the end of the course. So we could constrain it on top and on the bottom, some simple models to basically get from where we have measurements to places where we don’t.

CG: Gotcha, yeah. Well, I should ask, I mean, how deep is it?

MT: Well, I mean, there’s some uncertainties associated with that. But let’s say we get around 1,000 meters, so like short of 4,000 feet, or, yeah, (about) 3,500 feet. I’m talking from memory here, but from the ice surface up to things like Mount Dickey or Moose’s Tooth, we’re talking kind of 5,000 feet, something like that, above you already, right? And now you have another 3,500 feet below you. So, there’s this entire… you can sort of stand on that glacier, look at that landscape, and you can think about, you know, the whole thing inverted underneath you, as well, which is kind of an interesting thing to think about.

CG: Well I was gonna ask, I mean, like people that go out in the deep ocean, you know, they’ll look down and think about how deep the water is. Did you ever stand on that glacier and just think, “Oh my God, there’s so much ice beneath me?”

MT: Yeah, no, on any glacier, I think about that. Or sometimes, actually, even more if you go in formerly glaciated areas. Like I grew up in Switzerland, and where I grew up, that was all, you know, that was covered in ice. And you just sort of think, “How did this look like, you know, during the Ice Age, when at this level, high up on the side of the mountain, you were standing on solid ice?” Or you could do the same thing, and you go in a place like Glacier Bay, where at the terminus of the glacier right now, in Glacier Bay, the ice was 5,000 feet above sea level just 250 years ago, right? And so you can do it both ways. You can stand on a glacier and sort of wonder how it would be once this is gone.

But you can’t talk about glaciers these days without talking about climate change, right? I mean, that’s just because it’s so in your face, right? I mean, you know, it’s unbelievable the amount of changes, and it’s clear, it’s clear what’s behind it, right? But I also, you know, the reason a lot of us study glaciers is not that. The reason a lot of us study glaciers is just a fascination with them, and like what an awesome thing glaciers are, and how important they are in forming these big landscapes, right, carving out these big valleys and so on. So I just, when I talk to people about glaciers, I also want to get that across. Yes, it is kind of sad, you know? It makes me sad, too, to see see the glaciers disappear like that. But it’s also just trying to convey how magnificent these things are, right?

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