Current calcite (CaCO3) dissolution at the seafloor caused by anthropogenic CO2 (NCEI Accession 0176672)
Olivier Sulpis1, Bernard P. Boudreau2, Alfonso Mucci1, Chris Jenkins3, David S. Trossman4, Brian K. Arbic5, Robert M. Key6
Prepared by Alex Kozyr7
1GEOTOP and Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, QC, H3A 0E8, Canada
2Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax, NS, B3H 4J1, Canada
3INSTAAR, University of Colorado at Boulder, Campus Box 450, Boulder, CO, 80309-0450, USA
4Institute of Computational Engineering and Sciences, University of Texas-Austin, 201 E 24th Street, POB 4.102, Austin, TX, 78712-1229, USA
5Department of Earth and Environmental Sciences, University of Michigan, 2534 C.C. Little Building, Ann Arbor, MI, 48109-1005, USA
6Atmospheric and Oceanic Sciences, Princeton University, 300 Forrestal Road, Sayre Hall, Princeton, NJ, 08540-6654, USA
7NOAA, National Centers for Environmental Information, Ocean Carbon Data System (OCADS) , Silver Spring, MD 20910-3282, USA
Fig. 1 Anthropogenic fraction of the total calcite dissolution at the seafloor in 2002
This NCEI accession consists of current CaCO3 dissolution at the seafloor caused by anthropogenic CO2 in the World Oceans. This dataset contains the main results from Sulpis et al. (PNAS, 2018). All the variables have a 1x1 degree resolution. It can be used to compute calcite dissolution at the seafloor for changing bottom-water chemistry, calcite rain rates or current speeds, for instance. Oceanic uptake of anthropogenic CO2 leads to decreased pH, carbonate ion concentration, and saturation state with respect to CaCO3 minerals, causing increased dissolution of these minerals at the deep seafloor. This additional dissolution will figure prominently in the neutralization of man-made CO2. Yet, there has been no concerted assessment of the current extent of anthropogenic CaCO3 dissolution at the deep seafloor. Here, recent databases of bottom-water chemistry, benthic currents, and CaCO3 content of deep-sea sediments are combined with a new rate model to derive the global distribution of benthic calcite dissolution rates and obtain primary confirmation of an anthropogenic component. By comparing pre-industrial with present-day rates, we determine that significant anthropogenic dissolution now occurs in the western North Atlantic, amounting to 40-100% of the total seafloor dissolution at its most intense locations. At these locations, the calcite compensation depth has risen ~300 m. Increased benthic dissolution was also revealed at various hot spots in the southern extent of the Atlantic, Indian and Pacific Oceans. Our findings place constraints on future predictions of ocean acidification, are consequential to the fate of benthic calcifiers, and indicate that a by-product of human activities is currently altering the geological record of the deep sea.
Further details are in Sulpis, et al. 2018
The data set:
This dataset contains the main results from Sulpis, et al. 2018. All the variables have a 1x1 degree resolution. It can be used to compute calcite dissolution at the seafloor for changing bottom-water chemistry, calcite rain rates or current speeds, for instance. The diffusive boundary layer distribution can be used in any application requiring to solve chemical exchange through the sediment-water interface.
1. Current (2002) Calcite Compensation Depth (CCD): in [km]; depth at which the calcite rain rate equals its dissolution rate, see Sulpis et al. (PNAS, 2018)
2. Preindustrial Calcite Compensation Depth (PI_CCD): in [km].
3. Preindustrial calcite dissolution rate at the sediment-water interface (PI_r): in [mol/m2/a]
4. Current (2002) calcite dissolution rate at the sediment-water interface (r): in [mol/m2/a]
5. Botton current speed (u): in [m/s]; inferred from an inline computation of the annually averaged kinetic energy field of a nominally 1/25th degree global configuration of the HYbrid Coordinate Ocean Model (HYCOM), see Trossman et al. (Ocean Modelling, 2016)
6. Carbonate ion water-side mass transfer coefficient (beta): in [m/a]; it is simply the free solution diffusion coefficient for carbonate ion divided by the thickness of the DBL, and is computed here as a function of seawater viscosity and bottom-current speed, as explained in Sulpis et al. (PNAS, 2018)
7. Carbonate ion sediment-side mass transfer coefficient (ks): in [m/a]; it depends on the CaCO3 content of the sediment and is temperature-corrected
8. Carbonate ion overall mass transfer coefficient (kstar): in [m/a]; it is a non-linear combination of the water-side and sediment-side mass transfer coefficients
9. Calcium carbonate solid fraction in surface sediments (Xc): [no unit]; from the dbSEABED database compiled by Chris Jenkins at INSTAAR, see Jenkins (Sea Technol., 1997),Goff and Jenkins (Cont. Shelf. Reas., 2008) and http://instaar.colorado.edu/~jenkinsc/dbseabed/coverage/index.html>
10. Diffusive boundary layer thickness (zDBL): in [micrometers], computed as explained in Sulpis et al. (PNAS, 2018)
11. Longitude (lon): in degrees N
12. Latitude (lat): in degrees E
Acknowledgments and funding:
We thank all who contributed to the creation of GLODAPv2. We also thank John H. Trowbridge for valuable discussions. This research was funded by NSERC Discovery Grants to A.M and B.P.B. D.S.T. and B.K.A.ís contributions to this study were funded by the US National Science Foundation grant OCE-0960820 and PLR-1425989 to RMK.
Please cite this data set as:
Sulpis, Olivier; Boudreau, Bernard P.; Mucci, Alfonso; Jenkins, Chris; Trossman, David S.; Arbic, Brian K.; Key, Robert M. (2018). Current calcite (CaCO3) dissolution at the seafloor caused by anthropogenic CO2 (NCEI Accession 0176672). Version 1.1. NOAA National Centers for Environmental Information Dataset. doi: 10.25921/kbqy-4v05