(58k) Effects of Fossil Fuel CO2 emissions on the pH of the Oceans

Surface seawater samples from the Pacific, Atlantic, Gulf of Mexico, North Sea, Baltic Sea, Black Sea and the St. Lawrence Seaway were tested in-situ and under laboratory conditions for pH, CO₂ vapor pressure, and rates of CO₂ absorption. Laboratory tests were conducted on each sample under atmospheric CO₂ partial pressures of between 0ppm and 4000ppm. The pH of every sample = A – B.log_e(CO₂ vapor pressure), where A represents the pH when the sample CO₂ vapor pressure is 1ppm, and B is the slope of the logarithmic function. A is approximately 10.6 and B is approximately 0.4. The R² correlation for each sample was about 0.98. The in-situ tests confirmed NOAA data showing that CO₂ vapor pressure averaged 7% lower than the atmospheric CO₂ partial pressure. This difference is the driving force for CO₂ absorption by the oceans. The in-situ seawater pH ranged from 7.9 to 8.5 corresponding to CO2 vapor pressures of 410ppm to 250ppm. The average pH was 8.08 with a CO₂ vapor pressure of 378ppm. This study shows that the average surface seawater pH would decrease to 7.8 if the atmospheric CO₂ increased to 800ppm and to 7.2 if CO₂ increased to 4,000ppm. The increase in seawater acidity may be explained solely by the increases in fossil fuel CO₂ emissions. The average ocean pH could be maintained at 8.08 by reducing fossil fuel CO₂ emissions to 15Gt/year from approximately 35Gt/year. The longer this reduction in fossil fuel emissions is delayed, the lower the oceans pH will drop. The differential CO₂ concentration at the ocean surface results from the absorption and reaction of the dissolved CO₂ by plants, and the change in chemical equilibrium. This paper examines the causes of the observed variation in differential CO₂ concentration at the oceans surface.