Earth and Environmental Science 11–12 · Year 12
Floating ice against land ice: which raises sea level when it melts
Module 7: Climate Science
The idea
Floating ice already displaces its own mass of water, so in fresh water its melting does not change the level, whereas ice resting on land adds new water to the ocean.
What you need
- two identical clear containers with water to the same marked level; ice cubes of equal mass; a stone or an upturned cup in one container as land
- balance, ruler, marker, clock
How to do it
- Weigh equal masses of ice; float one set in container A and rest the other set on the land in container B, above the water.
- Mark both levels, leave to melt fully and mark again.
- Measure the change in each and calculate the expected rise in B from the mass of ice and the container area.
- Repeat with the ice in B half in the water to show the in-between case.
- Apply the result to sea ice, ice shelves, mountain glaciers and the Greenland and Antarctic ice sheets, stating which of them raise sea level when they melt.
What you should see
Container A’s level does not change within the reading precision; container B rises by the melted volume, about 1.0 L of water per kilogram of ice, divided by the water-surface area of the container. Ice is about 9 % less dense than liquid water (USGS Water Science School), so floating ice displaces its own mass of water and its melt water fills the space the submerged part occupied (Earthlearningidea). That holds exactly for the model, fresh ice in fresh water. Ice shelves are freshwater ice floating in seawater, and their meltwater, less dense than the seawater they displaced, takes up about 2.7 % more volume (seawater at salinity 35 and 20 °C 1024.76 kg/m³ against fresh water 998.21 kg/m³, computed with the UNESCO one-atmosphere equation of state), so melting ice shelves raise sea level slightly, while ice resting on land adds its whole volume.
What changes
- What you change
- where the ice sits (floating or on land)
- What you measure
- change in water level
- What you keep the same
- ice mass
- container size
- starting level
- room temperature
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Melting sea ice raises sea level.
- All Antarctic ice is floating.
Safety card
Hazards
No hazard is listed.
Controls
No control is listed.
Note
No hazardous chemicals or heat sources: record the activity in the school's RiskAssess risk assessment, following the NSW Department of Education Science safety and compliance page; the Chemical Safety in Schools package is not triggered.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES12-14EES11/12-1EES11/12-6EES11/12-7
- Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-12-03
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.
- www.nsw.gov.au/education-and-training/nesa/curriculum/science/earth-and-environmental-science-stage-6-2017
- www.earthlearningidea.com/PDF/322_Melting_ice_sea_level_1.pdf
- www.earthlearningidea.com/PDF/323_Melting_ice_sea_level_2.pdf
- www.antarctica.gov.au/about-antarctica/ice-and-atmosphere
- www.usgs.gov/special-topics/water-science-school/science/water-density