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Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer based separation technique, we estimate a global oceanic anthropogenic CO 2 sink for the period from 1800 to 1994 of 118±19 Pg C. The oceanic sink accounts for ~48% of the total fossil fuel and cement manufacturing emissions, implying that the terrestrial biosphere was a net source of CO 2 to the atmosphere of about 39±28 Pg C for this period. The current fraction of total anthropogenic CO 2 emissions stored in the ocean appears to be about one third of the long term potential.

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Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 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 CaCO3 dissolution rate for the global oceans is approximately 0.5 +/- 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3.

The absorption of atmospheric carbon dioxide into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. In order to better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of approximately 40-120 m along most transect lines and all the way to the surface on one transect off northern California. While seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO 2 has increased the areal extent of the affected area.

We quantify the oceanic sink for anthropogenic carbon dioxide (CO2) over the period 1994 to 2007 by using observations from the global repeat hydrography program and contrasting them to observations from the 1990s. Using a linear regression–based method, we find a global increase in the anthropogenic CO2inventory of 34 ± 4 petagrams of carbon (Pg C) between 1994 and 2007. This is equivalent to an average uptake rate of 2.6 ± 0.3 Pg C year−1and represents 31 ± 4% of the global anthropogenic CO2emissions over this period. Although this global ocean sink estimate is consistent with the expectation of the ocean uptake having increased in proportion to the rise in atmospheric CO2, substantial regional differences in storage rate are found, likely owing to climate variability–driven changes in ocean circulation.

[1] A simple function of sea surface salinity (SSS) and temperature (SST) in the form A T = a + b (SSS À 35) + c (SSS À 35) 2 + d (SST À 20) + e (SST À 20) 2 fits surface total alkalinity (A T ) data for each of five oceanographic regimes within an area-weighted uncertainty of ±8.1 mmol kg À1 (1s). Globally coherent surface A T data (n = 5,692) used to derive regional correlations of A T with SSS and SST were collected during the global carbon survey in the 1990s. Such regionspecific A T algorithms presented herein enable the estimation of the global distribution of surface A T when observations of SSS and SST are available. Citation: Lee, K.,