Why are sea-levels rising?
For over 100 years now sea-levels have been slowly rising. Scientists are telling us that this is due to the expansion of the sea as it increases in temperature but it is also due to the melting of land based ice, particularly the polar ice sheets on Greenland (North Pole) and Antarctica (South Pole) as well as our glaciers, like the ones we have here in New Zealand. Polar ice is made up of sea ice too but it is the melting of our land based ice which concerns us the most. But why? On the case is KCC member Sam, who has conducted an experiment to help us better understand how the ice in our sea and on our land can affect sea-level rises as it starts to melt.
You will need:
- Two clear plastic containers (enough to hold about 2 1/2 cups of water)
- A permanent marker
- A measuring cup
- Something that floats (we used a piece of bark, but you could try a milk bottle lid)
- A butter knife
- Water
- Ice cubes
What to do:
1. Fill the two containers halfway with water.
2. Create an island by putting your floating object in one of the cups.
3. Add two ice cubes to one container and mark the water level on the side of your container with the permanent marker.
4. Place an ice cube on your floating island. Pop it in the other container and mark the water level on the side of your container with the permanent marker.
North Pole with mainly sea ice and South Pole with mainly land ice
5. Wait for the ice to melt. Watch the ice on your island to make sure it doesn’t slip off. You want the water that melts to dribble down and into the cup.
6. Once the ice has melted, check the water level in each container again. Has it risen in any of the containers? If it has, why do you think this is?
What do you think will happen?
The water level in your container with an island will have risen more. When ice on land melts, water runs off and into the ocean – increasing its volume.
When sea-ice melts the sea-level stay the same. In the first picture the water mark has stayed the same as the original black line. When land ice melts the sea-level rises. In the second picture the water mark has risen above the black line.
Why did the water level in your container with no island stay the same? The floating ice is already taking up space in the ocean. When the ice melts, it just fills the space where the ice already was.
Want to do more?
Remember you can email a picture and explanation of your experiment to Paul Bennett, the government’s new minister for Climate Change? We need to tell Paula and the rest of the government that they need to act now to stop sea-level rising anymore and to protect all our habitats for future generations.
Small changes at home, like using less power, walking short distances instead of driving and buying locally grown food can all add up if everyone is doing their bit to make difference.
There are also some great websites and resources for you and your school like this one from Carbon Zero and the Climate Time Machine from NASA.
