Thermal Sea Level Rise Calculator
As the ocean absorbs heat it expands, raising sea level even before any ice melts. This thermosteric contribution is the rise in sea level caused purely by the thermal expansion of seawater. The height increase of a warming column equals the volumetric thermal expansion coefficient of seawater times the temperature change times the depth of the warmed layer. This calculator multiplies those three values, which you supply, to estimate the rise in metres, centimetres, and millimetres. The expansion coefficient is a user-editable input because it varies strongly with temperature, salinity, and pressure. The calculator covers thermal expansion only, not the separate contribution from melting land ice.
Thermosteric rise formula
Fractional expansion = alpha * delta T
Sea level rise (m) = alpha * delta T * depth
Sea level rise (cm) = rise m * 100
Sea level rise (mm) = rise m * 1,000
alpha is the volumetric thermal expansion coefficient of seawater in per kelvin, delta T is the warming in kelvin, and depth is the thickness of the warmed layer in metres.
Sea level context
- Thermal expansion (steric rise) and land-ice melt are the two main contributors to sea level rise.
- The expansion coefficient of seawater rises with temperature and is near zero in cold polar water.
- Expansion accumulates over the full depth of the warming column.
- This tool models the steric contribution only; melt water adds mass separately.
- NOAA and NASA maintain the global sea level observation record.
Thermal sea level rise: frequently asked questions
What is thermosteric sea level rise?
Thermosteric sea level rise is the increase in sea level caused purely by the thermal expansion of seawater as the ocean warms. Warmer water occupies more volume for the same mass, so a warming column of ocean grows taller. It is one of the two main contributors to sea level rise alongside the addition of melt water from land ice.
What is the formula for thermal expansion of the ocean column?
The rise equals the thermal expansion coefficient of seawater times the temperature change times the depth of the warmed layer: delta height = alpha times delta T times depth. The coefficient alpha has units of inverse kelvin, so the product is dimensionless times depth, giving a height in metres.
What thermal expansion coefficient should I use?
The volumetric thermal expansion coefficient of seawater varies strongly with temperature, salinity, and pressure, from near zero in cold polar water to roughly 0.0003 per kelvin in warm tropical surface water. Because it is not a single fixed number, it is a user-editable input you set for your conditions.
Does this include melting ice?
No. This calculator models only the steric (thermal expansion) contribution from a warming water column. The mass contribution from melting glaciers and ice sheets is separate and adds to the total observed rise. Combine both for a complete sea level budget.
Why does the depth of the warmed layer matter so much?
Expansion accumulates over the entire depth that warms. Heat has penetrated mainly the upper ocean so far, but the deeper the warming layer, the more total expansion for the same temperature change. Enter the thickness of the column you assume is warming.
Official sources
- NASA: Sea Level Change Portal.
- U.S. National Oceanic and Atmospheric Administration: Sea Level Rise.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.