DEFY SMCQUAID! #52: Ice is less dense than water, but….

The Question

Jocelyn asks:

This has been bugging me for a bit…
If ice is less dense than water, how come the Earth will flood when the polar ice caps melt? Wouldn’t the water level go down…or stay the same because of their height?

The Answer

Good question. I have a simple answer.

Yes, ice is less dense than water, hence, it floats. One would think that the displacement caused by the floating ice would simply fill when the ice melted. After all, your glass doesn’t overflow when the ice in it melts. (If this were the case, you might get more soda than ice when ordering a large from a fast food drive-through).

However, the bulk of the South Polar Ice Cap is NOT floating – it’s on land (Antarctica). Also, large portions of the North Polar Ice Cap are on land (Greenland, for example). It’s these ice sheets that, when melted, can raise the sea level.

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