Science 7–10 · Year 10

Land ice and sea ice: which one raises sea level

Science understanding: Earth and space sciences (NSW Stage 5 focus area: Environmental sustainability)

PracticalLow risk

The idea

Floating ice already displaces its own mass of water, so melting sea ice barely changes sea level, while ice that melts on land adds new water to the ocean.

What you need

2 identical clear containers with 15 cm x 15 cm bases (the NASA JPL lesson uses 6 inch containers)
modelling clay (or an upturned plastic tub topped with clay) to cover half of each base as land, about 6 cm high so its flat top stays above the water
ice cubes, 90 g for each container, weighed on a balance
tap water; a ruler with millimetre marks, or graph paper taped to each side
for the extension: salt water made from 35 g of salt made up to 1 L (NOAA gives about 35 g of dissolved salts per litre of seawater), a 100 mL measuring cylinder and a balance

How to do it

Press clay into half of each container. In container A put 90 g of ice on the clay (land ice); in container B put 90 g of ice on the floor beside the clay (sea ice).
Pour water into B until the ice floats with none resting on the bottom (about 4 cm deep for ordinary cubes, and deeper if any cube still touches), as the NASA JPL lesson directs; then pour water into A to the same level and mark both levels.
Read the water level in each container every 10 minutes until all the ice has melted.
Predict A's rise as the melted volume (90 mL) divided by the water's surface area.
Extension: repeat B with the salt water, first measuring its density by weighing 100 mL.
Run three trials and compare the mean rise in each container with the prediction.

What you should see

Container A rises by 90 mL / 112.5 cm^2 = 0.80 cm (8 mm) once all 90 g has melted and run off the clay into the water. Container B's level does not change within the 1 mm reading error in fresh water. In salt water the floating ice displaces its mass of the denser water, so the meltwater takes slightly more room: the extra volume is 90 g x (1 - 1 / rho) = 1.8 to 2.6 mL for a measured density of 1.02 to 1.03 g/mL, a rise of about 0.2 mm, too small for a ruler but real. The IPCC reports that ice-sheet and glacier mass loss were together the dominant contributors to global mean sea-level rise from 2006 to 2018. The learner knows it worked when A rises by 7 to 9 mm and B stays within 1 mm.

What changes

What you change: where the ice sits (on land or floating)
What you measure: change in water level
What you keep the same: mass of ice
container size
starting water level
room temperature

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

All melting ice raises sea level; floating ice has already displaced its own mass.
Melting Arctic sea ice is the main cause of sea-level rise; the IPCC names land ice sheets and glaciers as the dominant contributors.
Ice floats because it is lighter; a given volume of ice has less mass than the same volume of water.

Safety card

Low riskLearners carry it out

Hazards

water spilled on the floor

Controls

trays kept on the bench and spills wiped at once

Note

No hazardous chemical and no flame or heating apparatus: a generic classroom risk assessment (CSIS 1.7 or RiskAssess) covers trips, spills, warm lamps and sharp edges.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7-10 Syllabus (2023), NSW Education Standards Authority (implemented from 2026; codes read at curriculum.nsw.edu.au on 22 and 23 September 2026)SC5-ENV-01 SC5-WS-04 SC5-WS-06
Australian Curriculum v9AC9S10U04AC9S10I02AC9S10I05

Sources

The pages the author read to write this activity.

All Concept Studio activities