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Ice and water
Oceans and land
From National Science Education Standards: Natural hazards
Look outside. Can you see any ice? What about in the middle of summer? Believe it or not, about 10 percent of the planet's land is actually covered in ice—year round! The ice in these places, such as Antarctica or on very high mountain ranges, is usually in big pieces called glaciers or ice sheets. It can stay there if the temperature stays cool enough and enough snow falls to replace whatever ice melts off when the temperature gets above freezing.
All of that ice is made from an awful lot of water. And when that water melts, much of it ends up in the oceans. How might that affect us? We can get a fast-paced peek at this process that is going on right now with just a couple of ice cubes and some clay.
Antarctica is a solid continent just like North America or Asia. Because it gets so little warmth from the sun, it is cold enough to be covered with ice all year—at least for now. (The Arctic ice around the North Pole, on the other hand, is mostly covering ocean.)
But when average temperatures rise, as is happening in many places around the world because of climate change, big blocks of ice melt more quickly than they can grow during the winter. Thus, less moisture is trapped in ice sheets, then more is found in liquid form. And a lot of this extra water ends up in the oceans, leading, eventually, to higher sea levels.
Climate change is a shift in overall global temperatures and weather, and it is already affecting ice sheets and glaciers across the globe. When ice pieces fall off landmasses, such as Antarctica or Greenland, and into the ocean, the ice melts even faster. Scientists currently predict that sea levels will be at least three feet higher by 2100.
• Small bowl
• Ice cubes
• Modeling clay
• Warm water
• Pull off two portions of modeling clay. (Size will depend on the size of your bowl and the size of your ice cubes—they will need to be big enough for of them to hold two ice cubes on its surface and for both of them to stick out of the water.)
• Stick the clay to opposite sides of the bottom of your bowl.
• Mold one piece of clay to be flat, with a surface just large enough to hold two ice cubes. This will be Antarctica.
• Shape the other piece of clay so that it is slightly higher than the first piece—this piece will represent an ice-free continent where people live. Make some parts flat and give others hills or mountains.
• Place two ice cubes onto the lower flat piece of clay (Antarctica).
• Start slowly pouring the warm water into the bowl until it almost reaches the top of your Antarctica clay. Your other clay continent should still have area that is mostly well above water. The water represents the ocean.
• Because the air around the ice cubes is warmer than freezing (as it is now), what do you think will happen to the ice cubes? If you were able to keep the air around the Antarctica area below freezing, how would that change what happened to the ice cubes?
• Pour just a little bit more water into the bowl so that the water level just reaches the bottom of the two ice cubes. (In Antarctica, the ice actually extends beyond the land and over part of the ocean so some of it is in contact with water.)
• Note where the water level is on your dry continent clay by placing two toothpicks vertically into the clay where the water meets the clay. Compare the flat areas with the hilly ones.
• Watch as the ice cubes start to melt. What happens to the water level in the bowl?
• As it rises, position another toothpick or two to mark the new level.
• In Antarctica, Greenland and other places where big ice sheets are surrounded by the ocean, sometimes big chunks of ice fall into the ocean after they have started to melt. To replicate this process, push one of the ice cubes into the water. (You might notice waves hitting your dry continent—although this is closer than it a neighboring continent in the real world, scientists think that a big piece of ice could cause large waves to hit land far away.)
• Watch as the two ice cubes continue to melt. Which ice cube melts faster? What happened to the water level on your dry continent? Were the flat areas affected differently than the hilly ones?
Read on for observations, results and more resources.