Search

Author(s): James C. Orr (corresponding author) [1]; Victoria J. Fabry [2]; Olivier Aumont [3]; Laurent Bopp [1]; Scott C. Doney [4]; Richard A. Feely [5]; Anand Gnanadesikan [6]; Nicolas Gruber [...]

Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (C[O.sub.2]) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. 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 C[O.sub.2] to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic C[O.sub.2] emissions stored in the ocean appears to be about one-third of the long-term potential., Since the beginning of the industrial period in the late 18th century, i.e., over the anthropocene (1), humankind has emitted large quantities of C[O.sub.2] into the atmosphere, mainly as a [...]

The dissolution of aragonite particles in the ocean primarily depends on the degree of undersaturation of seawater with respect to that mineral. Most of the upper Atlantic Ocean, particularly north of 30[degrees]S and at depths of less than 2000 m, is supersaturated with respect to aragonite, whereas much of the deep Atlantic is undersaturated. Here we report, for the first time, shallow layers of aragonite-undersaturated water between 20[degrees]S and 15[degrees]N in the eastern tropical Atlantic. These layers are centered at 800 m and are surrounded by aragonite-supersaturated water above and below. This feature most likely results from a combination of chemical and biological processes including the uptake of anthropogenic C[O.sub.2] and the oxidation of organic matter falling from the highly productive overlying surface water. Reaction with protons resulting from these processes decreases the carbonate ion concentration and consequently the saturation state of the waters with respect to aragonite. The oceanic uptake of anthropogenic C[O.sub.2] during the industrial era has caused a significant increase in the size of the undersaturated layers. Future expansion will likely occur laterally to the west and south, where the degree of supersaturation is low compared to waters to the north. This expansion of the undersaturated layers is a prime example of how human activity during the industrial era has altered the upper ocean chemistry by injecting fossil fuel C[O.sub.2] into the ocean.

We estimated the oceanic inventory of anthropogenic carbon dioxide (C[O.sub.2]) from 1980 to 1999 using a technique based on the global chlorofluorocarbon data set. Our analysis suggests that the ocean stored 14.8 petagrams of anthropogenic carbon from mid-1980 to mid-1989 and 17.9 petagrams of carbon from mid-1990 to mid-1999, indicating an oceanwide net uptake of 1.6 and 2.0 ± 0.4 petagrams of carbon per year, respectively. Our results provide an upper limit on the solubility-driven anthropogenic C[O.sub.2] flux into the ocean, and they suggest that most ocean genera[ circulation models are overestimating oceanic anthropogenic C[O.sub.2) uptake over the past two decades., Despite improvements in our understanding of the partitioning of anthropogenic C[O.sub.2] between the atmosphere, ocean, and terrestrial biosphere, substantial uncertainties and insufficient direct observational constraints continue. Recent decadal-scale changes in [...]

The field measurements of pH, fugacity of carbon dioxide (fCO2), total inorganic carbon dioxide (TCO2) and total alkalinity (TA) on surface and deep waters from the Atlantic, Indian, Southern and Pacific oceans to determine the pK1, pK2 and pK2-pK1 is examined.

In their report 'Temporal trends in deep ocean Redfield ratios' (4 Feb., p. 831), Pahlow and Riebesell suggest that the marine biota has changed in the last few decades in [...]