• The goals of the intercomparison study were to understand potential sources of error and differences in ocean pCO2 systems and to develop guidelines for improving the systems and measurement practices.

• Conventional equilibrator-infrared systems used on ships along with the autonomous pCO2 systems (SAMI, CARIOCA, and MBARI systems) were used to measure the pCO2 in a large well-mixed pool.   

• The SAMI data are compared to the Nojiri NIES system (equilibrator-IR) system below.   

A pCO2 intercomparison of SAMI-CO2 and equilibrator-NDIR measurements during the National Institute for Environmental Studies (NIES) March 2003 intercomparison in Japan. Different pCO2 levels were measured in a large thermostated pool. The mole fraction (XCO2 ) is reported (pCO2  = XCO2 *barometric pressure). The equilibrator-NDIR was operated by NIES. The difference in the two measurements, the raw absorbances used to calculate the response and the sensor temperature measurements are also shown. The spikes in the D XCO2 are due to transient pCO2 signals when the pCO2 in the pool was changed.  See article