Ocean Acidification Calculator
Our marine ocean health calculator computes ocean acidification accurately. Enter measurements for results with formulas and error analysis.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
pH = 8.18 - 0.85 x log10(CO2 / 280)
Ocean pH estimated from atmospheric CO2 relative to pre-industrial (280 ppm, pH 8.18). Temperature and salinity adjustments refine estimate. Aragonite saturation indicates shell-building viability.
Worked Examples
Example 1: Current Conditions
Problem:CO2 420 ppm, temp 20 C, salinity 35, pH 8.07, projected 560 ppm.
Solution:pH drop=0.148\nCalc pH=8.032\nAcidity +40.6%\nProjected pH=7.924\nAragonite=3.32
Result:pH 8.032 | +40.6% acidity | Aragonite 3.32 (Moderate)
Example 2: Arctic High CO2
Problem:CO2 500 ppm, temp 5 C, salinity 33, pH 7.95, projected 700 ppm.
Solution:pH drop=0.214\nCalc pH=7.966\nTemp adj=+0.05\nSal adj=+0.004\nAdj pH=8.020
Result:pH 8.020 | Projected 7.843 | Arctic most vulnerable
Frequently Asked Questions
What is ocean acidification?
Ocean acidification is the ongoing decrease in ocean pH caused by absorbing atmospheric CO2. The ocean absorbs 25 to 30 percent of human CO2 emissions which reacts with seawater forming carbonic acid. Average surface pH has dropped from pre-industrial 8.18 to about 8.07 representing a 30 percent hydrogen ion concentration increase. The current acidification rate is roughly 10 times faster than any natural event in 300 million years.
How is ocean pH calculated from atmospheric CO2?
Ocean surface pH can be estimated from atmospheric CO2 using the carbonate chemistry relationship. When CO2 dissolves it forms carbonic acid which dissociates into hydrogen and bicarbonate ions. The pH decrease follows: delta pH = -0.85 x log10(CO2/CO2_preindustrial). This simplified formula captures seawater buffering capacity. Temperature and salinity modify the relationship with full calculations using multiple equilibrium constants.
How does temperature affect ocean acidification?
Temperature influences acidification through opposing mechanisms. Warmer water holds less dissolved CO2 suggesting less acidification. However carbonic acid dissociation increases with temperature partially offsetting reduced CO2 solubility. Tropical waters are generally less acidified but their lower carbonate concentrations make them more sensitive to further changes. Polar waters acidify first because cold water holds more CO2 with lower baseline saturation states.
How does salinity affect ocean pH?
Higher salinity generally corresponds to higher total alkalinity since dissolved ions contributing to acid-neutralizing capacity increase. Higher-salinity waters tend to have slightly higher pH and greater buffering capacity at approximately 0.002 pH units per practical salinity unit near average of 35 PSU. Estuarine and coastal areas with freshwater mixing have lower pH and reduced buffering making them more vulnerable to acidification impacts.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy