What are glaciers? Ask a glaciologist

What are glaciers? Ask a glaciologist
What are glaciers? Ask a glaciologist
Glaciologist Bethan Davies explains the science behind glaciers and how glaciers are a window into Earth's changing climate. Plus: Are there glaciers on other planets?
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BETHAN DAVIES: Glaciers are fundamentally, at their simplest, they're a pile of ice.


Hi. My name is Bethan Davies, and I'm a glaciologist. I study glaciers and how they've changed both today in the past and how they're going to change in the future.

Every winter, it snows in mountain regions or in polar regions. If that snow doesn't melt over the summer, then that snow remains in a pile over the summer. If over a lot of summers that snow starts to build up, you've grown a glacier. As that snow builds up and up and up, it really starts to put pressure and weight on the snow right at the bottom and it compresses it all. All the air gets kind of squeezed into tiny little chambers and becomes ice.

There are lots of different kinds of glaciers. At the biggest, we have ice sheets. We only have two ice sheets in the world today. We have the Antarctic Ice Sheet and the Greenland Ice Sheet. So if you go to The Alps, you'll see mountain glaciers. They will be the typical kind of form that you might see in a picture book. A kind of mountain glacier coming down.

In high latitude or polar regions, we have a lot of ice fields, which is basically where a lot of glaciers come together. So in Antarctica we've got this big huge ice sheet, and then all the way around it, these floating ice shelves. And they're mostly losing mass by blocks of ice breaking off and then floating away.

Other kinds of ice would be ice caps. They're small, but they're dome shaped, whereas an ice field would be less dome shaped to more kind of basin shaped.

There are glaciers and ice sheets in most continents and most places in the world, really. I think every continent has glaciers. There are glaciers on other planets. There are indeed glaciers on other planets. We know there are glaciers on Mars, or at least we think they're glaciers. They look like glaciers.

Mars also has polar ice caps just like Earth as well as little mountain glaciers around the planet. And we can look at them with satellite imagery, and they look just like Earth's glaciers. So there are definitely glaciers on other worlds.

Glaciers have been a really important part of the Earth's system for the last 2.4 million years. Over that time frame, the amount of ice in the world has grown and shrunk and grown and shrunk.

Glaciers are really strongly affected by warm summers. And what we're seeing a lot of at the moment is really, really warm summers. When you have warm summers, you melt that snowpack that's accumulated over the winter. And without that nourishment of snow staying over the summer, the glacier melts, the glacier becomes smaller.

So from both Antarctica and Greenland, the biggest impacts of climate change is going to be sea level rise. We're looking at about half a meter to a meter by the year 2100, mostly from glaciers of Greenland and Antarctica.

But glaciers are important for another reason. What the glaciers do is they retain snow and ice in the mountains. And then as they melt-- they melt in the summer, which is usually the dry season-- and people then use that water to irrigate their farms, to make hydropower for domestic consumption, and for industry.

And, in fact, a third of the world's population is dependent on water that's come from these mountain glaciers. 1.9 billion people worldwide rely on glacial melt water to sustain their lifestyle, to sustain their agriculture. So the impacts of global glacier mass loss is really, really significant, and it's likely to result in people having a shortage of water.

Glaciers also sustain the biodiversity of the mountain systems. So as we lose glaciers, we also see ecosystem impacts and we see change in ecosystems, change and impacts on the wildlife, the flora, and fauna. So glaciers are really important, and we should try and keep them where they are in the mountains.

The work that I've done in Antarctica has mostly been about trying to understand how glaciers have responded in the past to climate change. If we want to understand present day glacier change, we need to extend the record into longer term record.

Essentially, because glaciers build up year on year with that winter snowfall then remaining over the summer, if we go to the surface of the ice sheet, we can collect a core or a tube of ice, and then we can look at those layers in the ice. We'll have that white, bubbly winter ice layer from that winter snowfall and the clearer ice layer that's that summer melt ice fall. We can see these layers all the way down the ice core.

Within those layers, we have little bubbles of gas. And those little bubbles of gas tell us exactly what the past composition of the atmosphere was. So by taking a core of ice, we can tell things about past atmospheric composition, but also air temperature and global ice volume. So they're really important records of past climate. They can go back thousands and thousands of years and give us this really high resolution long record of past climate change.