Ocean Acidification pH Calculator

As atmospheric CO2 rises, oceans absorb more carbon dioxide, lowering seawater pH in a process called ocean acidification — and this calculator shows exactly how those changes play out under any conditions. Enter your atmospheric CO2 concentration, sea surface temperature, salinity, total alkalinity, and water depth into the Ocean Acidification pH Calculator to get the resulting Ocean pH. Secondary outputs include dissolved CO2, bicarbonate, carbonate, aragonite saturation, and dissolved inorganic carbon.

ppm

Current atmospheric CO2 level (pre-industrial: 280 ppm, current: ~420 ppm)

°C

Temperature at ocean surface

PSU

Practical Salinity Units (typical ocean: 35 PSU)

μmol/kg

Buffer capacity of seawater

m

Depth below sea surface (0 for surface)

Results

Ocean pH

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Dissolved CO2

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Bicarbonate (HCO3⁻)

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Carbonate (CO3²⁻)

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Aragonite Saturation (Ωar)

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Dissolved Inorganic Carbon

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Frequently Asked Questions

What is ocean acidification and how does it relate to pH?

Ocean acidification refers to the ongoing decrease in ocean pH caused by absorption of atmospheric CO2. As CO2 dissolves in seawater, it forms carbonic acid, lowering the pH from pre-industrial levels of 8.2 to current levels around 8.1.

How much has ocean pH changed since pre-industrial times?

Ocean surface pH has dropped from 8.2 to 8.1 since pre-industrial times, representing a 25% increase in hydrogen ion concentration. This may seem small, but pH is logarithmic, making this a significant change.

What is aragonite saturation and why is it important?

Aragonite saturation (Ωar) measures how easily marine organisms can build calcium carbonate shells and skeletons. When Ωar drops below 1, shells and coral skeletons begin to dissolve, threatening marine ecosystems.

How does temperature affect ocean acidification?

Warmer water holds less CO2 but chemical reactions proceed faster, affecting the carbonate system. Colder water absorbs more CO2, potentially experiencing greater acidification effects in polar regions.

What are the main carbonate species in seawater?

The main carbonate species are dissolved CO2, bicarbonate ions (HCO3⁻), and carbonate ions (CO3²⁻). As CO2 increases, more bicarbonate forms while carbonate decreases, affecting shell-building organisms.

Why does salinity matter for ocean acidification calculations?

Salinity affects the chemical equilibrium constants used in carbonate system calculations. Higher salinity changes the activity coefficients and solubility of carbonate minerals, influencing pH and saturation states.

How does water depth affect carbonate chemistry?

Deeper waters experience higher pressure, which affects CO2 solubility and carbonate mineral solubility. Deep waters are often naturally more acidic and closer to undersaturation for carbonate minerals.

What CO2 levels are predicted for the future?

Climate models project atmospheric CO2 could reach 500-1000 ppm by 2100 depending on emissions scenarios. This would further lower ocean pH to potentially 7.7-7.8, representing a 150% increase in acidity from pre-industrial levels.