NASA Nonsense

The tweet above is from @NASAClimate, a real official account from the real government organization that shoots rockets. (By the way, serious question: does anyone know why NASA does this instead of NOAA?)

If all of Greenland's ice melted, it would raise sea level ~23 ft. That's enough to put coastlines throughout the world under water.

As a bald statement, it sounds fairly reasonable. I wouldn't disbelieve it if it said anything from 20 to 40 feet; I'd get a bit doubtful if is said 100 feet.

But that said, that's a lot of ice, and melting ice takes a lot of energy. Let's just think about how much.

Ice, along with pretty much everything else, requires a certain amount of heat energy for the solid to turn into a liquid (or must lose a certain amount of heat energy to turn from a liquid back to a solid). This is called the enthalpy of fusion, which is a Greek-root phrase meaning "the amount of energy to turn a solid material into a liquid." It's also sometimes called the latent heat: it's the amount of heat energy lurking in water just by virtue of the water being liquid.

To understand what this means, let's set up our little home lab. Here's what we need:

Here's the lab setup:

  1. Fill the Erlenmeyer flask with a mixture of crushed ice and water.
  2. Set up the Bunsen burner and tripod, and put the flask on top. Put the thermometer into the flask, and connect it to your computer.

(Of course, you could do this with a pan of water on the stove, but that wouldn't be all science-y and stuff.)

Give this all a few minutes to settle down, and the water temperature will be right around 0°C.

Now light the burner, taking all the appropriate precautions; kids ask your parents' permission, hadda yadda.

Keep tracking the temperature. The Bunsen burner is pouring heat into the water, and the ice starts melting pretty quickly, but the temperature stays right at 0°C until the very last of the ice has melted. All of that heat from the Bunsen burner has gone into making the phase change from solid to liquid. That amount of heat energy is the enthalpy of fusion.

In fact, at 334 Joules per gram, water has the second highest enthalpy of fusion of any material. (First place goes to solid ammonia at 339 J/g).