Seawaterp H calculator
Free Seawaterp hcalculator Calculator for marine ocean health. Enter variables to compute results with formulas and detailed steps.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
pH = -log10([H+]), where [H+] is derived from carbonate equilibrium: CO2 + H2O <-> H2CO3 <-> H+ + HCO3- <-> 2H+ + CO3(2-)
Seawater pH is calculated from the carbonate equilibrium system using temperature-dependent dissociation constants (pK1, pK2), total alkalinity, and dissolved CO2 partial pressure. The Henderson-Hasselbalch relationship links alkalinity and CO2 to hydrogen ion concentration, which determines pH.
Worked Examples
Example 1: Tropical Coral Reef Assessment
Problem:A marine biologist measures seawater at a tropical reef: temperature 28C, salinity 35 ppt, total alkalinity 2300 umol/kg, atmospheric CO2 415 ppm, surface depth 0m. Is the water suitable for coral growth?
Solution:Using the carbonate equilibrium equations with T=28C, S=35, TA=2300, pCO2=415:\npH = approximately 8.05-8.10\nAragonite saturation (omega) = approximately 3.2\nCalcite saturation = approximately 4.8\nBicarbonate = approximately 2070 umol/kg\nCarbonate = approximately 184 umol/kg
Result:pH 8.07 with aragonite saturation of 3.2 indicates suitable conditions for coral growth, though slightly below pre-industrial values.
Example 2: Deep Ocean Carbon Storage Assessment
Problem:Oceanographers sample water at 2000m depth: temperature 2C, salinity 34.8 ppt, total alkalinity 2350 umol/kg, dissolved CO2 equivalent 600 ppm. Evaluate carbonate chemistry.
Solution:At depth with T=2C, S=34.8, TA=2350, pCO2=600, depth=2000m:\npH = approximately 7.7-7.8 (lower due to accumulated respiratory CO2)\nPressure correction: -0.2 pH units\nAragonite saturation drops significantly with depth\nCalcite saturation approaches 1.0
Result:pH 7.72 with aragonite saturation near 1.0 indicates water near the carbonate compensation depth where shell dissolution begins.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy