HR: 0800h
AN: OS31A-0546    [Abstracts]
TI: Increase of Anthropogenic CO$_2$ in the Atlantic Ocean in the Last Two Decades
AU: * Peng, T
EM: tsung-hung.peng@noaa.gov
AF: NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149 United States
AU: Wanninkhof, R
EM: rik.wanninkhof@noaa.gov
AF: NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149 United States
AB: The inorganic carbon data collected during the GEOSECS program in early 1970s represent results of the first systematic survey of total dissolved inorganic carbon (DIC) and alkalinity on a global scale. These data sets have become a critical component of studies of decadal variations of geochemical properties over the last thirty years. In particular, the oceanic uptake of anthropogenic CO$_2$ can be quantified from the increase in concentration of total dissolved inorganic carbon. It is essential that the historic data set be devoid of bias compared to recent high quality carbon data. The recent data has benefited from improvements in measuring techniques and the use of reference material. Results of re-evaluation of GEOSECS carbon data in the Atlantic Ocean by examining deep water properties at crossover stations between GEOSECS and WOCE cruises show that DIC measurements made in GEOSECS program are systematically higher than those made during recent WOCE/DOE global CO$_2$ survey. In the North Atlantic, the overall average offset is estimated to be 27 $\pm$ 9 umol/kg for DIC north of 15$^o$N. In the equatorial region between 15$^o$N and 15$^o$S, the mean DIC offset is 9 $\pm$ 11 umol/kg, and in the South Atlantic is 5 $\pm$ 5 umol/kg south of 15$^o$S. Applying the Multi-parameter Linear Regression method (MLR) to WOCE carbon data, DIC in the three latitudinal regions and separating the Western and Eastern Basins in the Atlantic Ocean is derived as a function of potential temperature, salinity, AOU, Silica and PO$_4$. After correcting GEOSECS DIC data, a residual DIC is computed between adjusted DIC and predicted DIC using the DIC equations derived from WOCE carbon data. The estimates of the increase in anthropogenic CO$_2$ based on these residual DIC indicates that the mean CO$_2$ uptake rate in the west basin is 0.70 mol/m$^2$/yr for the region north of 15$^o$N, 0.53 mol/m$^2$/yr for the equatorial region, and 0.83 mol/m$^2$/yr in the south Atlantic. In the east basin, the mean CO2 uptake rate is estimated to be 0.97 mol/m2/yr for the north Atlantic north of 15$^o$N, 0.57 mol/m$^2$/yr for the equatorial region, and 0.28 mol/m$^2$/yr for the south Atlantic south of 15$^o$S. The uncertainty of these estimates is high due to insufficient GEOSECS data and the quality of these background data is not as good as recent WOCE data.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4845 Nutrients and nutrient cycling
DE: 4215 Climate and interannual variability (3309)
DE: 4532 General circulation
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting