Antarctic Ice Sheet

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来自 The University of Chicago 的课程

全球变暖 I：气候变化的科学与建模

171 个评分

The University of Chicago

全球变暖 I：气候变化的科学与建模

171 个评分

This class describes the science of global warming and the forecast for humans’ impact on Earth’s climate. Intended for an audience without much scientific background but a healthy sense of curiosity, the class brings together insights and perspectives from physics, chemistry, biology, earth and atmospheric sciences, and even some economics—all based on a foundation of simple mathematics (algebra).

从本节课中

Potential Impacts

This unit we focus on the potential impacts of continued business-as-usual CO2 emissions. This is also the topic of the Working Group 2 volume of the IPCC reports (the Working Group 1 report is on the scientific basis, which is what we've been studying so far this course). You may find this material distressing, but hang on, because next week we'll go over "Mitigation", which is what it takes to avoid climate change (treated in the Working Group 3 report). Remember that most of the carbon we're worried about is still in the ground, so these impacts are inevitable only if we continue to decide to make them so. In Part II of this class, you can create a simple ice sheet model of your own.

Impacts of Sea Level2:01

Antarctic Ice Sheet2:52

Greenland Ice Sheet3:55

Paleo Sea Level Changes2:11

与讲师见面

David Archer
Professor
Geophysical Sciences

[MUSIC]

So the big behemoths in the sea level picture are the two ice sheets.

In Antarctica and in Greenland.

So here's something of a cross-section of the Antarctic Ice Sheet.

Here's the East Antarctic Ice Sheet that transcend Arctic mountains.

And the West Antarctic Ice Sheet.

So one thing that you can see is that the land

where the ice is sitting on, is actually lower than sea level

throughout much of the western part of the ice sheet.

So you may wonder how you could do such a thing like that.

How do you stick ice onto a piece of land that's underneath a whole bunch of water?

Well, turns out that the land was above the surface of the water when it formed,

but this process of isostatic adjustment, the weight of the ice,

gradually over millions of years, pushed the land down, and so

now the ice is extending down below sea level, it's grounded below the ocean.

So this leads to the possibility that if it starts to melt back a little bit,

the grounding line gets deeper and deeper as you melt it back, and so

that makes it easier and easier for the ice to float up off of the ground.

And once it floats up, it can flow in one of these things,

which is called an ice shelf.

So ice shelves can be hundreds of meters thick,

they're not like sea ice which is just a few meters thick.

They're like giant cliffs of ice that you can see,

and they are actually floating in the water.

So an ice shelf itself when it melts doesn't cause the sea level to rise,

because it was floating already.

But the ice shelf can act to sort of pen in

the outward flow of ice from the ice sheet itself.

And so, when these ice shelves crumble and

collapse as they you have seen them doing in the last few years,

they can allow the ice behind it to flow more quickly into the ocean.

The Greenland ice sheet in contrast is not grounded below sea level,

but it is extra vulnerable because it's warmer at the surface.

In Antarctica, the surface of the ice is always pretty much below freezing.

And so, the only way to melt the Antarctic ice sheet

is to flow it off into the water and melt it in the water.

Maybe let it drift away up into warmer climates.

[MUSIC]

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