The carbonate system in natural waters (original) (raw)

Solution of shallow-water carbonates: An insignificant buffer against rising atmospheric CO2

Geology, 2003

The shallow-water ocean environment is of great importance in the context of global change and is heavily impacted by human activity. This study evaluates the effects of human activity on the CO 2 exchange between the atmosphere and the surface water of shallow-water oceans. The evaluation is based on changes in net ecosystem metabolism, net ecosystem calcification, and atmospheric CO 2 concentrations, as seen in a processdriven biogeochemical box model. Numerical simulations show that this air-sea interface has probably served as a net source of CO 2 to the atmosphere for much of the past 300 years, but has recently switched, or will switch soon, to a net sink of CO 2 , because of rising atmospheric CO 2 and increasing inorganic nutrient load.

Overview of CO2-induced changes in seawater chemistry

2000

The most direct and predictable consequence of increased atmospheric CO 2 on coral reef environments is the shift in the carbonate equilibrium of seawater which results in lower pH and lower concentration of the carbonate ion (CO 3 2-). Many experiments have produced the remarkably consistent result that coral and algal calcification rates decrease in response to lowered [CO 3

Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans

Science, 2004

Rising atmospheric carbon dioxide (CO 2 ) concentrations over the past two centuries have led to greater CO 2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO 3 ) particles. Here we estimate the in situ CaCO 3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO 2 on CaCO 3 shellforming species. CaCO 3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO 3 dissolution rate for the global oceans is approximately 0.5 Ϯ 0.2 petagrams of CaCO 3 -C per year, which is approximately 45 to 65% of the export production of CaCO 3 .

Carbon Dioxide and Ocean Acidification

One of the results of Anthropogenic Global Warming is the acidification of the oceans which threatens wildlife on this planet. In this work it will be shown what will be the effect of carbon dioxide injected into the atmosphere, doubling the total amount from 350 ppm to 700 ppm. Principally the effect on carbonate ions CO3 2−. It is based on textbook chemical principles worked out by numerically solving the resulting non-linear equations by the bisection method. The results are the following: In a pure-water environment the effect is that carbonate ion concentration remains unaltered (i.e., no harm to coral reefs). In a constant-pH environment the carbonate ion concentration grows linearly with CO2 in the atmosphere (i.e., good for coral reefs). When lowering the pH by other means than CO2, the carbonate ion concentration drops linearly (i.e., bad for coral reefs). In some specific cases can raising the CO2 in the atmosphere slightly reduce carbonate ions in the oceans.

Modern-age buildup of CO 2 and its effects on seawater acidity and salinity

Geophysical Research Letters, 2006

The impacts of increases in atmospheric CO 2 since the midst of the 18th century on average seawater salinity and acidity are evaluated. Assuming that the rise in the planetary mean surface temperature continues unabated, and that it eventually causes the melting of terrestrial ice and permanent snow, it is calculated that the average seawater salinity would be lowered not more than 0.61% from its current 35%. It is also calculated-using an equilibrium model of aqueous carbonate species in seawater open to the atmosphere-that the increase in atmospheric CO 2 from 280 ppmv (representative of 18th-century conditions) to 380 ppmv (representative of current conditions) raises the average seawater acidity approximately 0.09 pH units across the range of seawater temperature considered (0 to 30°C). A doubling of CO 2 from 380 ppmv to 760 ppmv (the 2 Â CO 2 scenario) increases the seawater acidity approximately 0.19 pH units across the same range of seawater temperature. In the latter case, the predicted increase in acidity results in a pH within the water-quality limits for seawater of 6.5 and 8.5 and a change in pH less than 0.20 pH units. This paper's results concerning average seawater salinity and acidity show that, on a global scale and over the time scales considered (hundreds of years), there would not be accentuated changes in either seawater salinity or acidity from the observed or hypothesized rises in atmospheric CO 2 concentrations.

The influence of the partial pressure of carbon dioxide on the total carbonate of seawater

Marine Chemistry, 1982

The dependence of the total carbonate concentration of ocean water on temperature and atmospheric partial pressure of carbon dioxide is calculated. The results show that the increase in total carbonate caused by the increase of carbon dioxide in the atmosphere is ca. 25-50 times larger than the precision in the experimental determination of Ct.