Basic science: understanding numbers
Basic science: understanding numbers

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Basic science: understanding numbers

2.3.1 Volume of the Greenland ice sheet

Previously, you were given the area for the Greenland ice sheet. To work out the volume, you will need to have an idea of how thick it is. We don’t know exactly how thick it is at every location, but you can work out a fairly good estimate.

You can work out an upper limit for the volume by knowing that it is about 3,000 m, or 3 km, thick at its thickest, so multiplying the area (1,710,000 km2) by the thickness (3 km) gives a maximum volume of 5,130,000 km3for the ice on Greenland.

But the ice is thinner in places, so what is the lower limit? At the edges of the ice sheet, the thickness of the ice tails off to a few tens of metres. If you assume a minimum thickness of 50 metres, or 0.05 km, you get a value of 1,710,000 multiplied by 0.05, or 85,500 km3 as the lowest estimate of the volume of the ice. This is still a lot of ice!

You can get a much better idea of the volume of ice, however, by using the average thickness. This has been worked out, from borehole drilling and radar measurements, to be about 1,500 m, or 1.5 km.

Activity 2.1 Calculating the volume of the Greenland ice sheet

Allow about 15 minutes

If you multiply the area of 1,710,000 km2 by 1.5 km, you get a value of 2,565,000 km3 for the volume of the ice on Greenland. Use the internet to look up official estimates of the volume of ice on Greenland and share them in the forum thread for this activity [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] . How do you think we did using the simple area and average thickness? Discuss this point with your fellow students.

In the next section, you will look at why ice floats on water, when you discuss density.

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