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Scientist explains how a crumbling glacier could shrink coastlines globally


Near the southern tip of this planet, the world's widest glacier is on the verge of collapse. The Thwaites Glacier is an ice shelf the size of Florida. It sits on the western edge of Antarctica, and it's responsible for 4% of the world's sea level rise. That's earned it the nickname The Doomsday Glacier. Scientists have been observing it for decades because it's become a case study in how human-driven climate change is felt most on the Earth's poles.

This week, a group of scientists announced findings that it could collapse within five years. That would accelerate global sea rise. Erin Pettit is part of that group, called the International Thwaites Glacier collaboration. She's a glaciologist at Oregon State University, and she's been studying this particular glacier for decades. Pettit says the Thwaites Glacier is like a huge river of ice draining into the ocean, and it's happening at a troubling rate. She explains why.

ERIN PETTIT: Temperatures are rising in the atmosphere. That's creating different winds, and those winds are causing different currents in the ocean. That is bringing up this warm, deep water that normally doesn't have access to the ice. But it's bringing that warm, deep water up to the ice, and it's causing it to melt from the underside. And then it's fracturing in places. And the lower part of this glacier looks like it might do over the next few years is shatter into hundreds of icebergs.

PFEIFFER: For you, as someone who studies this, what's your sense of alarm as you watch this?

PETTIT: My sense of alarm is it's unsettling. This is not going to cause instant sea level rise. So what this is doing is taking away a bit of resistance, a stabilizing feature of the lower part of the glacier, sort of like a dam that's holding back water. We're taking away this resistive force that's holding it back and allowing it to accelerate.

PFEIFFER: So you say it's unsettling, if not alarming. Then, for people who are concerned about climate change, what should their level of concern be about this happening?

PETTIT: So a couple of things. The instability within the glacier is hard for us to slow and stop right away. But by thinking about what we're doing in the atmosphere, we can have an impact over the next few decades. The other thing, the thing that we really need to be careful about, I feel like, is thinking about, how do we really want to treat our coastlines and our coastal communities in terms of the real impact of sea level rise over the next couple of years? Because we are not going to be able to stop at least some of that sea level rise. We can slow it in the long term, but there is going to be some measurable sea level rise that we won't be able to stop. And I think it's in those communities where we've already built up. We need to make some decisions about, do we want to continue to rebuild where we have? Do we want to just build a higher seawall? Do we want to rethink the coastlines in anticipation of continued sea level rise over the next few decades?

PFEIFFER: And then, what sort of effects could we see as a result on global sea levels?

PETTIT: Because this ice is already floating it, already has contributed what's going to contribute to sea level. So there will not be an immediate jump in sea level, but we will start seeing an accelerated contribution from the Thwaites Glacier. It's contributing about 4% to global sea level rise, and that will start creeping up towards 4.5% to 5%, which sounds small, but it actually is the biggest single contributor glacier to sea level rise. And even a centimeter of sea level rise has important impacts for the coastlines because it makes the high tides higher, because it makes the storm surges bigger for the same sized storm, because it enhances erosion along the coastlines. So a tiny bit of sea level rise gets amplified when it interacts with our coastlines.

PFEIFFER: If that's what's likely to happen eventually, then what's the takeaway from the report? What needs to happen?

PETTIT: What needs to happen - (laughter) I am not a policy expert, but I think we all need to take a hard look at what we do on a day-to-day basis. And the policy, our local community policies can be as important as international policies and agreements that we make towards reducing our impacts, no matter where we live. And then thinking hard about how we want to move forward in our coastal areas.

PFEIFFER: You don't sound as alarmed about this as I assumed you would.

PETTIT: It's - I want to turn this into something where we can feel empowered to make change and that we have the power to make the right decisions for the communities that are going to be most impacted and make the right decisions for the Earth as a whole. So I don't feel like it helps for me to express panic. I would rather think positively about our ability as a society to start to make some of the right decisions towards mitigation and prevent the impacts that come back to our coastal communities.

PFEIFFER: Before we let you go, I think you started researching glaciers more than two decades ago. Is that right?

PETTIT: I did, yeah.

PFEIFFER: I'm wondering if, at the beginning of your career, you had a sense back then of how rapidly these glaciers would deteriorate, and if your perspective has changed in any way over time?

PETTIT: When I started, we actually thought that much of the Antarctic and the Greenland ice sheet were rather slow-changing masses of ice. We've learned a lot and seen a lot. And the amazing satellite data we've been able to capture in more detail over the last two decades, we've started to understand these systems better. But yeah, when I started, we had no idea that things were going to change this rapidly.

PFEIFFER: Is it shocking to see the pace?

PETTIT: That part is very shocking. I'm used to looking at mountain glaciers and seeing them retreat because we climb up into the mountains. I enjoy climbing up into the mountains and looking at the glaciers. And that is alarming in itself, seeing the shrinking glaciers in our local mountains. But I never quite expected to see this dramatic of change this quickly. We knew that some things were possible. We knew that there was change happening. We just never quite anticipated that it would be happening this rapidly.

PFEIFFER: That's Erin Pettit. She's a glaciologist at Oregon State University and part of a team studying the Thwaites Glacier in Antarctica. Professor Pettit, thanks for your time.

PETTIT: Thank you. Transcript provided by NPR, Copyright NPR.