# Optical Absorbance Ratio at 620nm (CO2ABS2)

pCO2 of seawater is measured using a colorimetric reaction by injecting a pH-dependent indicator solution into a sample of seawater and measuring the absorbance of that mixture at two wavelengths. The ratio of absorbance between those two wavelengths is then used to calculate pCO2. Optical Absorbance Ratio at 620nm refers to the ratio of absorbance of the seawater sample with and without the pH indicator solution at a wavelength of 620 nm.

### Instrument Classes

The following instrument classes include this data product:

Typical Units
unitless

Sampling Regime
Water Column