Educator Guide: What's Causing Sea-Level Rise? Land Ice Vs. Sea ...

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What's Causing Sea-Level Rise? Land Ice Vs. Sea Ice
Overview
In this activity, students 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. Prior to the activity, students will predict what each situation will do to the level of water and then compare their prediction to what they observe.
Management
This activity can be done in groups or as a whole-class demonstration. The materials list above is for one group or one whole-class demonstration.
This activity takes time, as a given quantity of ice has to melt. If you have students all day, the activity can start at the beginning of the day and be revisited at regular intervals throughout the day. If students meet for only a class period, consider accelerating the ice melt by placing the experiment near a warm lamp or a source of mild warmth.
Be aware that the ice in the water will melt faster than the ice on the “land.”
Be sure the clay surface will allow the melted land ice to flow into the body of water. Avoid pressing your fingers into the clay and creating depressions that will block the flow of water.
Background
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 contain giant ice sheets that are also considered glaciers. As temperatures rise, 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 also melt in warm temperatures but are not significant contributors to sea level rise. This is because they are already in the water. The volume of water they displace as ice is about the same as the volume of water they add to the ocean when they melt. As a result, sea level does not rise when sea ice melts. While density differences between salt water and freshwater result in a difference between the volume of salty sea water being displaced by sea ice and the freshwater that would result from the melting of that sea ice, it is minimal and beyond the scope of this lesson.
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.
Procedures
As a class, discuss sea-level rise and climate change. Tell students they’re going to conduct an experiment to learn how melting ice contributes to sea-level rise.
Ask students where there is a lot of ice on Earth. 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.)
Ask students which type of ice, if any, contributes more to sea-level rise. Ask students to explain their thinking.
On the student data sheet, have students record their prediction about which type of ice will contribute more to sea-level rise.
Provide each group with the required materials and directions to conduct the 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.
In one tub, place as many ice cubes as possible on the flat clay surface. This represents land ice.
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 the student data sheet.
You can mark the water level with a marker on the outside of the tub, but if the containers are reused, they will have the marks from the previous group. Another way to mark the water level is to mark a line in the clay using a pencil or other object.
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.
Use the measurements recorded on the data sheet to create a line graph representing the water level in each tub.
Discussion
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?
Assessment
Students should make a prediction and provide reasoning for their prediction. The accuracy of their prediction is not as important as the fact that they made one and can communicate their reasoning.
Groups should build the land-ice and sea-ice containers according to the directions.
Groups should take measurements and record data at regular intervals.
Groups should compare their results to their predictions and provide a reasonable explanation for what they observed.
Students should be able to connect the model to the global events of ice melting and associated sea-level rise.
Extensions
Use the data from the student data sheet to create a line graph using spreadsheet software.