Tag: University of Alaska Fairbanks

Imagine a valley filled with ice, from wall to wall, miles wide.  This is a photograph that I took of the Taku Glacier in Alaska when I first saw it, from an airplane:

What’s underneath all that ice?  How deep does the ice go?  Are there streams underneath?  Rocks? Mud?  This is what scientists want to know about glaciers–we need to know how much ice they have and what they are traveling over in order to know how fast they will melt and cause sea level rise.  But we can’t just dig up a glacier to see what’s underneath–the Taku Glacier (pictured above) is 1000 feet thick!  The Taku Glacier once floated on the ocean, where the warmer water melted it rapidly, and the tides pulled off icebergs.  The glacier shrank because of this, until it was protected from the ocean tides by a thick layer of mud.  But the mud is washing away, so someday the glacier will be in the open ocean again.  So we wanted to see how much mud is left.

We cannot see what is underneath the ice, but we can hear it.  If you had a metal thermos and you wanted to know how much liquid was left inside, you could tap on the metal to give you an idea about whether it was mostly full or mostly empty.  For a thick glacier, you need to tap hard to listen to the echoes.  Last spring, when there was still snow on the ground, we took a helicopter to the Taku Glacier and tapped hard on it–with explosives!  (They weren’t big enough to hurt the glacier.) We spent ten days on the ice surface doing our survey.  The view from camp looked like this…

…just a white expanse of 1000-foot-thick ice, hiding everything underneath.  But by recording the echoes under our feet, we learned that there is still a layer of mud down there, dozens of feet thick.  We’ll tap again in 2016 to see how much mud will have been lost in two years.

– Jenna, University of Alaska Fairbanks, USA

The weather reports you watch on TV come from people who take measurements of today’s weather, and then let computers predict how it is going to change in the next few days. I do the same thing for the Juneau ice field, which is a large glacier next to Alaska’s capital of Juneau. I feed the results of the measurements into the computer, and the computer model tells me how fast the Juneau ice field is going to shrink in the next 100 years.

When we know the future of Juneau ice field better, we can better predict how fast its neighbors are going to shrink, and therefore how much they are all going to contribute to global sea level rise. This helps the authorities in coastal planning, which may need to include determining how high dykes need to be in the future to withstand the rising oceans.

– Florian, University of Alaska, Fairbanks, USA

What do you think of when you hear someone say “climate change”? Maybe you think of sea level rise, maybe fossil fuel usage, or maybe the future of polar bears. I think of computer modeling. The idea of computer modeling can seem intimidating at first, but it is one of the most powerful and exciting tools we have in order to make decisions about how to adapt our communities in a changing world.

When I was in second grade, my class made a model volcano from paper mache, chicken wire, and baking soda and vinegar. Though it didn’t work exactly like a real volcano, it helped contribute to my understanding of volcanoes and chemical reactions. (And as a bonus it was fun and messy!) Now, I’m modeling glaciers. Instead of having a physical model of paper mache, I have a series of equations in a computer. These equations describe how a glacier melts, grows, and flows. They aren’t always perfect, because they are an idealization of the very complicated processes that occur in ice and snow – some of which we don’t fully understand yet – but they do a good job at replicating the way we have observed glaciers changing over many years.

Once we know that the equations that we have to describe a glacier are a reasonable representation of reality, we can conduct experiments using this model. If we want to know what could happen to glaciers if the temperature warms up and the amount of rain increases, we can change the variables in our model, and then run the model to find out. It is impossible to conduct this experiment in reality. We can’t go to a glacier and warm up the air around it to see what happens, right? (Though, in a sense that is what is happening with climate change, but it is important that we understand the possible results of this experiment, instead of just waiting to find out). We know that climate change will have drastic effects on glaciers. Using a model allows us to consider how those effects might unfold before they happen, so that we have a chance to make decisions about adapting our water ways, agricultural systems, and other infrastructure connected to glaciers.

I will be starting my graduate school and research journey this coming fall at the University of Alaska Fairbanks. At this point, I’m not sure what my specific research question will be, but I do know that I want to model how glaciers could change in the future, and what that means for communities that rely on the water resources from those glaciers. Glaciers are a critical freshwater source for people around the world, and we need to start thinking about how access to that water will change as glaciers change, and about what things we can put in place to lessen the forces of a changing world. It is easy to think of computer modeling as trying to predict the future, but nobody and no model can do that. Instead, computer modeling provides a space to consider possible scenarios of an uncertain future, and I’m excited to explore these scenarios in my research and hopefully provide relevant information for communities that are tied to glaciers and their changes.

– Aurora, University of Alaska Fairbanks, USA

When you see the Greenland Ice Sheet for the first time, it’s very difficult to understand, intuitively, that it’s undergoing significant changes.  It’s enormous, and very still.  The nearest simile I can come up with is that it’s like looking at the ocean in slow motion.  With a closer look, however, you start to notice all the strange and subtle things that are occurring.  At the ice edges, the landscape is like a construction site, as the ice bulldozes rocks into haphazard piles.  Moving inland, you notice rivers, not unlike the ones perhaps meandering through your town, but carving their channels through ice and flowing impossibly fast due to their steepness and smoothness (sometimes they just disappear into frightening voids in the ice).  Moving even further up, you’ll find yourself in a snow-swamp or on a lakeshore, both of which mark the beginning of the portion of the glacier that never melts.  Even higher towards the top of the ice cap, if you spend enough time there, you may find that you start to notice subtle hills and valleys that are barely noticeable amidst the expansive, blank, white plain.  The cycle of snow turning to ice, ice melting into water, and water running off the surface and down into the depths of the glacier are on display here, and each part of this cycle is connected with its other parts. The trick is knowing where to look for these connections.

It’s important to understand, however, the difference between observing all of the (understated) drama at the surface of an ice sheet, and understanding how they are all connected in a way where you could start to make predictions.  It’s even more difficult to extrapolate these observations to things that you can’t see, like where does all of that water flowing off of the surface, and into holes in the ice, go?  Does it reach the bottom of the ice sheet and flow into the ground, or does it get squeezed out the sides of the ice sheet between the glacier and the bedrock?  And do these questions even matter for humans, particularly in the context of a changing climate?  As it turns out, the answer to this last question is very likely yes. What happens to water at the surface is very important in determining how much of the Greenland Ice Sheet turns into water that goes into the ocean, even beyond the amount that melted in the first place.  The answer to the question of where does the water flowing into holes go, is that it mostly gets squeezed out the sides.  We know this because there are very large rivers that flow out from under the ice sheet at its edges. 

Thus, we can watch water go in, and we can watch water go out, but what happens in between?  This is a very difficult problem.  How do you observe the bed of an ice sheet?  One thing that we can do is to drill holes through the ice and measure the pressure of the water, and what the bed of the glacier looks like.  These are powerful measurements, and they can tell us many things, like how fast the water is flowing, how long it’s been since the water flowed in from the surface (if that’s where it came from), and how hard it’s pushing back on the ice above it.  This last bit is important because ice can, in some cases, when the water pushes back hard enough, float.  When this happens, the ice starts to slide, and the ice sheet can start to deliver more ice to low elevations (where it’s warm), or directly into the ocean, which is what drives sea level rise.  So why not just drill holes everywhere?  Drilling a hole through an ice sheet is incredibly expensive, and we couldn’t possibly drill enough to say something about what the water is doing everywhere on an ice sheet bed.

The alternative, and what I do in my research, is to come up with models that simulate the movement of water under an ice sheet, as well as the ice itself (because ice is fluid when it gets deep enough).  This sounds complicated, and in a practical sense, it is.  However intuitively, a model ice sheet operates much like a model airplane; the parts are simplified and scaled down into a machine that we can work with at home, in the office, on a computer.  This allows us to make educated guesses about what might be happening down there (hypotheses, if you will), and to test them without having to go to the ice every time.  We determine how good our hypotheses are by comparing the results of our models with the data that we collect in the field (like the pressures that we measure in the few holes in the ice that we have the resource to drill).  More often than not, we get it wrong; but this is a great opportunity to rethink our beliefs about the factors that influence glacier movement.  Sometimes this means that we learn about some key piece of data that we didn’t know that we needed, and this educates what we do in the field next time.  This process of trial and error is ongoing, and makes for an exciting research environment, where we continually test and reform the theory about ice sheet movement, made more exciting by the importance of ice sheets to climate change.  And it’s very satisfying when you find that your snippet of computer code accurately simulates some component of the natural world.

– Doug, University of Alaska Fairbanks, USA