This file describes the following data base: CDIAC DB1012: A GLOBAL 1 DEGREE by 1 DEGREE DISTRIBUTION OF ATMOSPHERIC/SOIL CO2 CONSUMPTION BY CONTINENTAL WEATHERING AND OF RIVERINE HCO3 YIELD Contributed by: Philippe Amiotte Suchet and Jean-Lue Probst Centre National de la Recherche Scientifique Center de Geochimie de la Surface Strasbourg Cedex, France April 1995 TABLE OF CONTENTS I. INTRODUCTION II. METHODOLOGY III. DATA DESCRIPTIONS IV. CDIAC QUALITY ASSURANCE PROCEDURES V. CHEMICAL SYMBOLS VI. REFERENCES, FURTHER READINGS, & DATA SOURCES I. INTRODUCTION The mission of the Centre National de la Recherche Scientifique (CNRS) of Strasbourg Cedex, France is to study "The Global Carbon Cycle and its Perturbation by Man and Climate, the Terrestrial Biosphere". With the support of the Environment Programme of the European Communities, modeling of the spatial distribution of atmospheric-soil CO2 consumption by chemical weathering of continental rocks have been and are being conducted. One of the major results of these studies is a set of global maps which show the distribution of CO2 consumption (FCO2) and the transport of bicarbonate (FHCO3-) from rivers to the ocean, each in moles per kilometer squared per year (mol km2/yr). Continental weathering influences the geologic carbon cycle (Trabalka, 1985). The largest natural exchange fluxes of carbon occur between the atmosphere and the terrestrial biota, and between the atmosphere and the ocean surface waters (Houghton, et. al. 1990). River carbon input to the oceans is a component of the estimate of global air-sea CO2 fluxes (Sarminento and Sundquist 1992). It is estimated that about 0.3 gigatons of carbon per year (GtC/yr) are consumed by the chemical erosion of continental rocks and transferred as HCO3- to the oceans (Berner et. al. 1983; Meybeck 1987; and Probst 1992), while the flux of particulate and dissolved organic carbon transported by rivers to the oceans is estimated to be about 0.4 GtC/yr (Probst 1992). On the whole, about 0.7 GtC/yr are transferred by continental erosion from the soil-biosphere reservoir to the oceans. A model developed by Amiotte Suchet and Probst (1993) calculates the flux of atmospheric-soil CO2 consumed by the chemical erosion of continental rock (i.e., rock weathering) and the bicarbonate river transfer to the ocean. This model is based on a set of empirical relationships between FCO2 and the drainage (runoff) on the major rock types outcropping on the continents. The model assumes that the consumption of atmospheric CO2 by continental weathering is primarily influenced by drainage, and the different types of rocks outcropping the continents. This data base contains estimates of the net flux of atmospheric-soil CO2 (FCO2) produced by the Amiotte Suchet and Probst model and the associated bicarbonate river flux (FHCO3-). These variables are referenced to a 1 degree latitude by 1 degree longitude world grid. The grid contains 64,800 records (i.e. grid cells) originating at -180 degrees West longitude by -90 degrees North latitude, and extending to 180 degrees West longitude by 90 degrees North latitude. II. METHODS This database contains global estimates of the flux of atmospheric-soil CO2 consumed by the chemical erosion of continental rocks (FCO2) and of the total bicarbonate flux from rivers to the oceans (FHCO3-). These estimates are the result of a four phased process: the identification of the empirical relationships between FCO2 and drainage for major rock types; the development of a model, GEM-CO2, to estimate FCO2 and FHCO3-; the validation of GEM-CO2 using three case studies; and the global application of GEM-CO2. The initial phase began under the assumption that the consumption of atmospheric-soil CO2 by chemical weathering is primarily influenced by drainage, and air temperature (Amiotte Suchet and Probst, 1992; Probst 1992; Probst et. al. 1992) and by the physical and chemical characteristics of weathering rocks (Probst et al., 1994). The HCO3- ions measured in surface waters mainly come from carbonate material dissolution and from atmospheric-soil CO2 used in the chemical weathering of silicate and carbonate minerals (Amiotte Suchet and Probst 1993). During the weathering of silicate rocks, all the HCO3- ions released in solution come from atmospheric CO2. For example consider the following reaction in albite hydrolysis: 2(NaAlSi3O8)+2(CO2)+11(H2O) --> Al2Si2O5(OH)4+2(HCO3-)+2(Na+)+4(H4SiO4) During the weathering of carbonate rocks, only half of the HCO3- ions released in solution come from atmospheric CO2. For example consider the following reaction in calcite dissolution: CaCO3 + CO2 + H20 --> Ca^2 + 2(HCO3-) These reactions and others imply that in a monolithologic drainage basin, the flux of atmospheric CO2 consumed by rock weathering can be estimated from the flux of bicarbonate ions transported by stream waters at the outlet of a basin, and form the basis of GEM-CO2 (Amiotte Suchet and Probst, 1993). The relationships between FCO2 and drainage were calculated using data published by Maybeck (1986) on the drainage (runoff) and concentrations of the major dissolved elements for 232 French monolithological drainage basins. For each watershed, the bicarbonate river flux (FHCO3-) was calculated using the drainage (Q) and the HCO3- concentration measurements. The atmospheric CO2 consumed by rock weathering was considered equal to the total HCO3- flux for streams draining silicate rocks and equal to half the HCO3- flux for streams draining carbonate rocks. Furthermore, Rock weathering increases when drainage increases and varies by rock type. Under this assumption, the empirical relationship between FCO2 and drainage was then determined for each rock type as indicated in Table 1. --------------------------------------------------------------------- --------------------------------------------------------------------- Table 1. Relationships between FCO2 and Drainage (Q) (Amiotte Suchet and Probst, 1993). --------------------------------------------------------------------- Relation FCO2 - Q(2) Indices ---------------- ---------- FCO2=aQ CO2 Rock Type a r ICO2 IE Flux ------------------------- ----- ----- ---- ---- ---- 1. plutonic & metamorphic 0.095 0.92 1.0 1.0 0.9 2. sands & sandstones 0.152 0.71 1.5 1.3 1.5 3. acid volcanic 0.222 0.98 2.3 2.2 4. evaporitic 0.293 0.99 3.1 4.0 2.9 5. basalts 0.479 0.98 5.0 4.8 6. shales 0.627 0.95 6.6 2.5 6.3 7. carbonate 1.586 0.98 16.7 12.0 15.9 -------------------------------------------------------------------- a = the relationship between the flux of atmospheric-soil CO2 consumed by rock weathering and the runoff for each rock type r = Pearson correlation coefficient ICO2 = relative index of chemical erosion IE = Weathering rate of a given rock type vs weathering rate of granitic rocks -------------------------------------------------------------------- -------------------------------------------------------------------- Since the lithologies of the French watersheds are representative of the major rock types which outcrop the continents, the relationships identified in Phase 1 were incorporated into the next phase, the development of GEM-CO2. Since the proportion of carbonate materials in rocks is highly variable and difficult to estimate, GEM-CO2 assumes that only carbonate and evaporitic rocks contain any carbonate materials. This assumption is not correct, therefore the relationship between FCO2 and the drainage intensity for shale rocks may be subject to caution. In phase three, GEM-CO2 was verified and validated using three large river basins: the Amazon and Congo basins in tropical equatorial climates, and the Garonne (France) in temperate climate (Amiotte Suchet and Probst, 1993). Each river basin was divided into small grid cells and treated as a monolithologic drainage basin for which the drainage intensity and lithology were determined from maps (see section VI). Table 2, which follows, summarizes the findings in each study area and illustrates that the GEM-CO2 estimates are realistic. The differences in FCO2 between GEM-CO2 estimates and other studies can be partly attributed to differences in the drainage intensity of the period which has been considered (Amiotte Suchet and Probst, 1993). ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ Table 2. Case Study Findings. ------------------------------------------------------------------------------ -------------------------------------------------------------------- | GEM-CO2 ESTIMATES | OTHER STUDIES | | | (Using Field Measurements) | ----------|---------------------------|--------------------------------------| | Study | FCO2 | FCO2 | FCO2 to | FCO2 | FCO2 to | Data | | Basin | Spacial | Mean | FHCO3- | Mean | FHCO3- | Sources | | | Variability| | | | | | |---------|------------|------|---------|------|---------|-------------------| | | | | | 310 | 64.6% | Probst et al. 1993| | Amazon | 14-3600 | 271 | 67.8% | | | | | | | | | 285 | 70.5% | Stallard 1980 | |---------|------------|------|---------|------|---------|-------------------| | | | | | | | | | Congo | 14-400 | 65 | 79.8% | 53 | 74.7% | Probst et al. 1994| | | | | | | | | |---------|------------|------|---------|------|---------|-------------------| | | | | | 441 | 55.0% | Etchanchu 1988 | | Garonne | 13-2400 | 224 | 57.0% | | | | | | | | | 113 | 55.0% | Semhi et al. 1993 | | | | | | | | | |---------|------------|------|---------|------|---------|-------------------| | FCO2 values * 10^3 moles/km2 yr. | |----------------------------------------------------------------------------| ------------------------------------------------------------------------------ The final phase, applied GEM-CO2 is on a global scale, using a 1 degree longitude by 1 degree latitude grid consisting of 64,800 cells. The grid originates and -180 degrees West longitude by -90 degrees North Latitude and extends to 180 degrees West longitude by 90 degrees latitude. For each grid cell, a mean lithology was determined using lithological and soils maps published by the FAO-UNESCO (1971, 1975, 1976, 1978, and 1981) for each continent. The drainage intensity was calculated after Willmott 1985 using mean monthly precipitation data supplied by the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. GEM-CO2 used these data to produce the data variables, FCO2 and FHCO3-, within this database. These global results show that the consumption of CO2 is mainly localized in the Northern hemisphere, because of its large proportion of carbonate rocks; and in equatorial regions because of their very humid climates. III. DATA DESCRIPTIONS This data base consists of the files listed in Table 3. ----------------------------------------------------------------------- ----------------------------------------------------------------------- Table 3. The files in CDIAC DB1012. ----------------------------------------------------------------------- File File Logical File Number Name Records Size Format ------ -------- ------- ----------- -------------------------- 1 readme 593 26,933 Flat ASCII file 2 gem.asc 64,800 2,592,000 Flat ASCII file 3 gem.e00 64,801 50,129,910 ARC/INFO Version 7.0 TM Exported coverage file 4 gem.for 35 1,342 Flat ASCII file 5 gem.sas 6 110 Flat ASCII file ----------------------------------------------------------------------- ----------------------------------------------------------------------- File 1, README, is a file that contains general information about the contents of this database, which you are currently reading. File 2, GEM.ASC, is a flat ASCII file containing estimates of the flux of the atmospheric-soil CO2 consumed by the chemical erosion of continental rocks (FCO2) and the bicarbonate flux from rivers to the ocean (FHCO3-). The data values for each grid cell are representative averages of the entire grid cell. Grid cells without estimates are indicated by values of -9999.99 for FCO2 and FHCO3-. Data was not estimated for Greenland or Antarctica, therefore grid cells in these regions will have -9999.99 values. GEM.ASC is formatted as follows in table 4: ----------------------------------------------------------------------- ----------------------------------------------------------------------- Table 4. Format for GEM.ASC. ----------------------------------------------------------------------- 10 read(5,100,end=999) id, long, lat, fco2, fhco3 100 format (i5,2f8.2,2f9.2) ----------------------------------------------------------------------- ----------------------------------------------------------------------- The variables in GEM.ASC are illustrated in Table 5 as they appear in file 2. --------------------------------------------------------------------- --------------------------------------------------------------------- Table 5. Variable Descriptions for Files GEM.ASC. --------------------------------------------------------------------- Variable Column Variable Variable Name start end Type Description -------- ----- ----- -------- --------------------------------- GEM-ID 1 5 Integer Grid cell identification number. LONG 6 13 Real Longitude location expressed in decimal degrees of the center of the 1 degree by 1 degree grid cell. LAT 14 21 Real Latitude location expressed in decimal degrees of the center of 1 degree by 1 degree grid cell. FCO2 22 30 Real The flux of atmospheric-soil CO2 expressed in moles per km2 per year. FHCO3 31 39 Real The bicarbonate river flux, expressed in moles per km2 per year. -------- ----- ----- -------- ------------------------------------ * A value of -999.99, for variables FCO2 and FHCO3 denotes a grid cell without a data value for the specified flux variable. ---------------------------------------------------------------------- ---------------------------------------------------------------------- File 3, GEM.E00, is an exported ARC/INFO TM Version 7.0 polygon coverage. This coverage was originally exported from a UNIX Work- station with the "none" option (i.e., EXPORT COVER GEM GEM NONE). The NONE option of the ARC/INFO EXPORT command specifies no compression and allows this coverage to be compatible among multiple ARC/INFO platforms and versions. In order to read this file you must copy it into an ARC/INFO workspace; run the ARC/INFO IMPORT Command (i.e., IMPORT COVER GEM.E00 GEM); and execute the ARC/INFO EXTERNAL command (i.e., EXTERNAL GEM). The coverage, GEM, has 64,801 records, 1 more record than it's ASCII equivalent, GEM.ASC. This additional record is unique to ARC/INFO TM as it specifies ARC/INFO's world polygon. An ARC/INFO world polygon refers to the boundary extent of the coverage. This additional record is the first record in the polygon attribute table (i.e., .pat). It contains 0 values for each real variable within the coverage (i.e., 0 values for variables long, lat, FCO2, and FHCO3). Once imported, GEM 's polygon attribute table (.pat) should appear as shown in Table 6: ------------------------------------------------------------------ ------------------------------------------------------------------ Table 6. Items Listing of GEM.PAT ------------------------------------------------------------------ 8 ITEMS: STARTING IN POSITION 1 COL ITEM NAME WDTH OPUT TYP N.DEC ALTERNATE NAME 1 AREA 4 12 F 3 5 PERIMETER 4 12 F 3 9 GEM# 4 5 B - 13 GEM-ID 4 5 B - 17 LONG 8 8 F 2 25 LAT 8 8 F 2 33 FCO2 8 8 F 2 41 FHCO3 8 8 F 2 ------------------------------------------------------------------ ------------------------------------------------------------------ File 4, GEM.FOR, contains the Fortran 77 retrieval code to read and write GEM.ASC (file 2). A listing of GEM.FOR follows in Table 7. ------------------------------------------------------------------ ------------------------------------------------------------------ Table 7. Contents of file GEM.FOR. ------------------------------------------------------------------ c********************************************************* c* fortran program to read and write gem.asc (file 2 ) * c********************************************************* integer nlin integer id real long, lat, fco2, fhco3 c********************************************************* c* initialize a counter and open files for input/output * c********************************************************* nlin=0 open(unit=5,file='gem.asc',readonly,status='old') open(unit=6,file='gem.out',status='new') c********************************************************* c* read/write the data variables * c********************************************************* 10 read(5,100,end=999) id, long, lat, fco2, fhco3 if (nlin.gt.63) nlin=0 if (nlin.eq.0) write (6,110) nlin=nlin+1 write(6,105) id, long, lat, fco2, fhco3 20 continue go to 10 100 format (i5,2f8.2,2f9.2) 105 format (1x,i5,2f8.2,2f9.2) 110 format (4x,'id',3x,'long',5x,'lat',4x,'fco2', 1 6x,'fhco3',/,26x,'in mol km2/yr') c*********************************************************** c***** close files and end ****** c*********************************************************** 999 close(unit=5) close(unit=6) stop end ------------------------------------------------------------------ ------------------------------------------------------------------ File 5, GEM.SAS, is printed in Table 8, and contains SAS TM retrieval code to read and write GEM.ASC (file 2). ------------------------------------------------------------------ ------------------------------------------------------------------ Table 8. Contents of file GEM.SAS. ------------------------------------------------------------------ options nodate nonumber nocenter; data gem; infile 'gem.asc'; input id long lat fco2 fhco3; proc print; run; ------------------------------------------------------------------ ------------------------------------------------------------------ IV. CDIAC QUALITY ASSURANCE PROCEDURES The data within this database were originally received as two ASCII files. One file contained estimated flux values for the atmospheric-soil CO2 consumed by chemical weathering (FCO2) while the other contained estimates for the mean annual bicarbonate flux transported by surface water (FHCO3-), both expressed in moles per kilometer squared per year (mol km2/yr). Additionally, the files each contained longitude and latitude coordinates which represented the center point location of a 1 degree by 1 degree grid cell and were expressed in decimal degrees. Both files were read into SAS on a unix workstation, and compared using the SAS COMPARE Procedure. Because both files contained the same longitude and latitude coordinates, the files were merged into a single file containing the variables: longitude, latitude, FCO2, and FHCO3 respectively. The composite file was then read into an ARC/INFO TM Version 7 Geographic Information System (GIS), and plotted over a 1: 2,000,000 digitized world coastal outline map. The map was then examined for reasonableness. V. CHEMICAL SYMBOLS Al = Aluminum Ca = Calcium C = Carbon CaCO3 = Calcite (i.e. Calcium Carbonate) CO2 = Carbon Dioxide FCO2 = The flux of atmospheric-soil CO2 consumed by the chemical erosion of continental rocks H = Hydrogen H2O = Water HCO3- = Hydrocarbon-trioxide FHCO3- = The bicarbonate flux from rivers to the ocean O = Oxygen Na = Sodium NaAlSi3O8 = Albite (i.e., Sodium Aluminum Silicate) VI. REFERENCES, FURTHER READINGS, AND DATA SOURCES Amiotte Suchet, P. 1995. Cycle du Carbone, Erosion Chimique des Continents et Transferts vers les Oceans. Sci. Geol. Mem., 97, Strasbourg, 156 p. Amiotte Suchet, P. and J.L. Probst. 1995. A Global Model For Present Day Atmospheric/Soil CO2 Consumption by Chemical Erosion of Continental Rocks (GEM-CO2). Tellus, 47B, pp. 273-280. Amiotte Suchet, P. and J.L. Probst. 1993. Modeling of Atmospheric CO2 Consumption by Chemical Weathering of Rocks: Application to the Garonne, Congo, and Amazon Basins. Chemical Geology, 107: pp. 205-210. Amiotte Suchet, P. and J.L. Probst. 1993. CO2 Flux Consumed by the Chemical Weathering of Continents: Influences of drainage and lithology. C.R. Acad. Sci. Paris, t. 317, Serie II, pp. 615-622. Amiotte Suchet, P. and J.L. Probst. 1992. Flux de CO2 Atmospherique Consomme par Erosion Chimique des Continents et Transfert de Carbone du Reservoir Biosphere-sol vers les Oceans. 14e R.S.T., Toulouse, Soc. Geol. Fr. Ed. Paris, 5 pp. Berner, R.A., Lasaga, A.C. and R.M. Garrels. 1983. The Carbonate-Silicate Geochemical Cycle and its Effect on Atmospheric CO2. Amer. J. Sci., 283: pp. 641-683. Etchanchu, D., Geochimie des eaux du Bassin de la Garonne, Transfert de Matieres Dissoutes et Particulaires vers l Ocean Atlantique, Thesis de Doctorat, Universite Paul Sabatier, Toulouse, 1988, 178 pp. Department of Energy. 1985. John R. Trabalka (ed.). Atmospheric Carbon Dioxide and the Global Carbon Cycle. DOE/ER-0239. Carbon Dioxide Research Program, Washington, D.C. Houghton, J.T., G.J. Jenkins, and J.J. Ephraums. 1990. Climate Change: The IPCC Scientific Assessment. Cambridge University Press, New York, New York. Meybeck, M. 1987. Global Chemical Weathering of Surficial Rocks Estimated from River Dissolved Load. Amer. J. Sci., 287: pp.401-428. Nkounkou R.R. and J.L. Probst. 1987. Hydrology and Geochemistry of the Congo River System. Mitt. Geol. Palaont. Inst. Univ. Hamburg, SCOPE/UNEP Sonderband, Heft 64, pp. 483-508. Probst, J.L.,Mortatti, J., and Y. Tardy, 1994. Carbon River Fluxes and Global Weathering CO2 Consumption in the Congo and Amazon River Basins. Appl. Geochem., 3: pp.1-13. Probst, J. L. 1992. Geochimie et Hydrologie de l'Erosion Continental - Mecanismes, Bilan Global Actuel et Fluctuations au cours des 500 Derniers Millions d'annees. Sci. Geol., Mem., 94, Strasbourg, 167 pp. Probst, J.L., Amiotte Suchet, P., and Y. Tardy. 1992. Global Continental Erosion and Fluctuations of Atmospheric CO2 Consumed During the last 100 years. Proc. 7th Intern. Symp. W.R.I., Park City, Utah, USA, pp. 483-486. Sarmiento, J.L., and E.T. Sundquist. 1992. Revised Budget for The Oceanic Uptake of Anthropogenic Carbon Dioxide. Nature (London), 356: pp. 589-593. Semhi K., Probst, J.L., Etcheber, H., and A. Bazerbachi. 1993. Dissolved River Transport in the Garonne Basin - Seasonal and Interannual Variations. In: EUG VII, Strasbourg, Abstract Supplement no. 1 to Tarra Nova, 5: 633 pp. Stallard R.F., 1980. Major element geochemistry of the Amazon river system. PhD. Thesis, MIT-WHOI Joint Program in Ocean- ography, Cambridge MA., 362 pp. DATA SOURCES B.R.G.M. (Bureu de Recherche Geologiques et Minieres) 1980. Carte Geologique de la France et de la Marge Continentale a l echelle de 1:1,500,000, BRGM ed., Orleans. B.R.G.M. (Bureu de Recherche Geologiques et Minieres) 1983. Precipitations Efficaces Moyennes Annuelles en France (1946-1776) - carte a 1:1,500,000, Rapport BRGM 83 SNG 003 EAU, Orleans. FAO-UNESCO (Food and Agriculture Organization - U.N. Educational, Scientific, and Cultural Organization). 1971, 1975, 1976, 1978, 1979, 1981. Soil Map of the World. Vol. I to Vol. X., UNESCO Press, Paris. UNESCO (U.N. Educational, Scientific, and Cultural Organization). 1977. Atlas of World Water Balance. UNESCO Press, Paris. Willmott C.J., Rowe, C.M., and Y. Mintz. 1985. Climatology of the Terrestrial Seasonal Water Cycle. J. of Climatology, 5: pp. 589-606.