Sea level is rising, in part, because melting glaciers on land are adding more water to Earth’s oceans. Glaciers—large sheets of ice and snow—exist on land all year long. They are found in the mountains of every continent except Australia. Greenland and Antarctica are home to giant ice sheets that are also considered glaciers. As temperatures rise from climate change, glaciers melt faster than they accumulate new snow. As these ice sheets and glaciers melt, the water eventually runs into the ocean, causing sea level to rise.
Icebergs and frozen seawater (known as sea ice) also melt in warm temperatures but do not cause sea level to rise. This is because they are already in the water. Think about the last time you had a beverage with ice: As the ice melted, did your cup overflow? It did not because the volume of water the ice displaced is the same as the volume of beverage in your glass. The same goes with sea ice and icebergs: They do not add to the volume of the ocean when they melt. As a result, sea level does not rise when sea ice melts.
Another contributor to sea-level rise is the increase in volume that occurs when water is heated, called thermal expansion. Both thermal expansion and ice melt are the results of the rise in global average temperatures on land and sea known as climate change.
Sea-level rise puts birds in danger. As ocean levels rise, coastal ecosystems like beaches and marshes flood more often. Birds that live and nest on beaches and in marshes can’t always escape in time. Their homes are suddenly not safe places to live. Sea-level rise puts other animals, places, and people in the same danger, where their home is no longer safe. That is why it’s important that we all work together to stop climate change.
In this activity, kids will learn about sea ice and land ice. They will observe ice melting on a solid surface near a body of water and ice melting in a body of water. They will see how they affect sea-level rise differently with their own eyes.
Two food-storage containers, ideally identical ones
Clay or play-dough (if unavailable, see modifications below)
Tray of ice cubes
- Start by discussing some of the above information. Ask your child where there is a lot of ice on Earth, using a globe or map if it’s helpful. Ask them to specify if the ice is on land or at sea. (The Greenland and Antarctic ice sheets, along with smaller mountain glaciers, are considered land ice. The ice in the Arctic is frozen seawater and therefore considered sea ice.)
- Introduce the idea of climate change—have they heard of it before? What do they know? Explain that climate change is making Earth warmer. What does your child think will happen to the planet’s ice as Earth gets warmer?
- Ask your child what kind of ice melt contributes more to sea level rise: Land ice (like glaciers) or sea ice (like icebergs)? This is the hypothesis for your experiment.
- Press equal amounts of clay into one side of each plastic tub, making a smooth, flat surface representing land rising out of the ocean.
Note: If you do not have clay or playdough, there are many variations to try. The goal is to have the ice floating in water in the sea-ice container, and placed outside the water in the land-ice container so that the meltwater will drain into the tub. You can place the ice in a strainer or funnel placed or held above the tub to represent land; strategically place a lid on a slope to drain into the container; or any number of other creative solutions. You can even hold the ice in your hand and have the meltwater drain through your (chilly!) fingers.
- In one tub, place as many ice cubes as possible on the flat clay surface. This represents land ice. Alternatively, place the cubes inside your strainer or other land-ice vessel.
- In the other tub, place the same number of ice cubes on the bottom of the tub, next to the clay. This represents sea ice.
- Pour water into the sea-ice container until the ice floats. Be sure no ice is resting on the bottom of the tub. The water shouldn’t be higher than the land level.
- Without disturbing the ice cubes, pour water into the land-ice container until the water level is about equal to the water level in the sea-ice container.
- Using the ruler, measure the water level (in millimeters) in each tub and record the data on a piece of paper. You can also mark the water level with a marker on the outside of the tub if you don’t mind potentially long-term marks.
- At regular intervals, measure the water level and record it on the data sheet. Compare the water level with the marked line in the clay. Allow the ice in both tubs to melt completely. This might take some time, and the sea ice will melt faster than the land ice—which is true on Earth, too. To speed things along, you can place the containers under a lamp or in sunlight, or direct heat from a hair dryer onto the cubes.
- After the ice has melted, talk about the results. In which container did the water level rise more? How does this compare to your prediction? Why do you think this occurred? In what way is this related to global sea-level rise? Does the melting of Earth’s glaciers contribute to sea-level rise? How about the melting of icebergs? What animals might be hurt if sea levels rise? What does this tell us about why it’s important to stop climate change?
This activity is adapted for home from a classroom lesson plan by NASA’s Jet Propulsion Laboratory.