Sea Level Rise from Ice Melt Calculator
Estimate eustatic sea level rise from land ice mass loss, in millimeters, using the standard 361.8 gigatonnes-per-millimeter ocean conversion.
🧊 What is Sea Level Rise from Ice Melt?
Eustatic sea level rise is the rise in global sea level caused by adding new water mass to the ocean, primarily from melting land ice such as mountain glaciers, the Greenland Ice Sheet, and the Antarctic Ice Sheet. Unlike thermal expansion, which changes sea level by expanding the water already in the ocean, eustatic sea level rise happens because entirely new water enters the ocean system from land, directly increasing the total volume the ocean basins must hold.
Climate scientists and glaciologists use eustatic sea level rise estimates constantly, to convert satellite gravimetry measurements of ice sheet mass balance (such as data from the GRACE and GRACE-FO missions) into an equivalent sea level contribution, to attribute how much of the observed rise in global mean sea level comes from each individual ice source, to project future sea level rise under different ice sheet melt scenarios, and to compare the relative importance of Greenland, Antarctica, and mountain glaciers as sea level contributors.
A common misconception is that all melting ice raises sea level. It does not. Sea ice, which already floats in the ocean, has already displaced its own weight in water and adds essentially nothing to sea level when it melts, the same reason a melting ice cube does not overflow a full glass. Only land ice, glaciers, ice sheets, and ice caps sitting above sea level, adds genuinely new mass to the ocean when it melts and reaches the sea. Another misconception is that ice sheet melt is the only sea level driver. In reality it works alongside thermal expansion as one of two roughly comparable major contributors.
This calculator applies the standard gigatonnes-to-millimeters ocean conversion so you can quickly translate any ice mass loss rate and time period into an eustatic sea level rise contribution, and compare it against typical rates from Greenland, Antarctica, and mountain glaciers.
📐 Formula
This is a straightforward mass-balance conversion (per IPCC AR6 Working Group I, Chapter 9), not a model of how or why ice melts. It assumes a constant mass loss rate over the period entered.
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Greenland's Recent Average Loss Rate
270 Gt/yr (Greenland's recent average) sustained for 10 years
Example 2 — Antarctica's Recent Average Loss Rate
150 Gt/yr (Antarctica's recent average) sustained for 20 years
Example 3 — A Large Single-Year Mass Loss Event
1000 Gt lost in a single year (a hypothetical major ice-shelf collapse event)
❓ Frequently Asked Questions
🔗 Related Calculators
What is eustatic sea level rise?
Eustatic sea level rise is the rise in global sea level caused by adding new water mass to the ocean, mainly from melting land ice such as glaciers, the Greenland Ice Sheet, and the Antarctic Ice Sheet. It is distinct from thermosteric sea level rise, which comes from ocean water expanding as it warms rather than from new mass being added.
What formula does this calculator use for sea level rise from ice melt?
It uses delta SLR (mm) = mass lost (Gt) / 361.8, based on the ocean's surface area of roughly 361.8 million square kilometers. Since 1 gigatonne of water equals 1 cubic kilometer, spreading that volume evenly over the ocean's surface area raises the average level by about 1/361.8 mm per gigatonne.
Where does the 361.8 Gt-per-mm conversion factor come from?
It comes directly from the ocean's surface area. The global ocean covers approximately 361.8 million square kilometers. Adding 361.8 cubic kilometers of water (361.8 Gt, since 1 Gt of water occupies 1 cubic kilometer) spread evenly across that area raises sea level by exactly 1 millimeter.
How much ice is Greenland losing per year?
Recent satellite gravimetry and altimetry studies estimate the Greenland Ice Sheet has been losing mass at an average rate of roughly 270 gigatonnes per year in recent decades, though the rate varies considerably from year to year depending on summer melt intensity and ice flow dynamics.
How much ice is Antarctica losing per year?
Recent estimates put Antarctic ice sheet mass loss at roughly 150 gigatonnes per year on average in recent decades, concentrated mainly in West Antarctica and the Antarctic Peninsula, while parts of East Antarctica have been closer to stable or even gaining mass in some studies.
Do melting mountain glaciers contribute much to sea level rise?
Yes. Even though mountain glaciers outside Greenland and Antarctica hold far less total ice, their combined mass loss rate, roughly 270 gigatonnes per year in recent global assessments, is comparable in magnitude to Greenland's contribution and has historically been one of the largest single sources of eustatic sea level rise.
Does melting sea ice raise sea level?
No, not measurably. Sea ice already floats in the ocean and has already displaced its own weight in water, so its melting does not add new mass and barely changes sea level (the same principle as ice cubes melting in a full glass of water). Only land ice, glaciers, ice sheets, and ice caps, adds new mass when it melts and runs into the ocean.
How does ice melt sea level rise compare to thermal expansion sea level rise?
They are two separate physical mechanisms. Ice melt adds new water mass to the ocean from land ice. Thermal expansion adds no mass at all, it simply expands the water already in the ocean as it warms. See the companion Sea Level Rise from Thermal Expansion Calculator, which uses the formula delta SLR = alpha x delta T x D, for the warming-based contribution.
Can I combine this calculator's result with the thermal expansion calculator for a total estimate?
Yes. Total observed sea level rise is approximately the sum of the eustatic (ice melt) contribution from this calculator and the thermosteric (thermal expansion) contribution from the companion calculator, plus smaller terms like land water storage changes that neither tool covers.
Is the mass-loss rate assumed constant over the years I enter?
Yes, this calculator applies a simple constant annual rate multiplied by the number of years you enter. Real-world ice sheet and glacier mass loss rates accelerate or vary over time, so use this as a straightforward linear projection rather than a full ice-sheet model forecast.
What does a 1 mm sea level rise actually look like in ice mass terms?
About 361.8 gigatonnes of ice would need to melt and reach the ocean to raise global mean sea level by 1 mm. For scale, that is roughly 1.3 years of Greenland's recent average mass loss rate, or about 2.4 years of Antarctica's recent average mass loss rate.