HR: 14:55h
AN: OS23F-06    [Abstracts]
TI: Changes in the $^{13}$C/$^{12}$C of Dissolved Inorganic Carbon in the N. Atlantic along A16N between 1993 and 2003
AU: * Quay, P
EM: pdquay@u.washington.edu
AF: University of Washington, School of Oceanography Box 355351, Seattle, WA 98195 United States
AU: Stutsman, J
EM: johnnys@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 355351, Seattle, WA 98195 United States
AB: The $^{13}$C/$^{12}$C of dissolved inorganic carbon ($\delta$$^{13}$C-DIC) was measured at 12 stations during the Repeat Hydrography A16N section (between 6$\deg$S and 61$\deg$N along 20-25$\deg$W) in summer 2003 and compared to $\delta$$^{13}$C-DIC measurements in summer 1993 along the same cruise track. In the surface layer, the $\delta$$^{13}$C-DIC in 2003 is consistently lower by up to 0.5 $\permil$ compared to 1993, with the largest decrease occurring north of 40$\deg$N. After normalizing for changes in phosphate, there remains a consistent surface $\delta$$^{13}$C-DIC decrease of up to 0.3 $\permil$. The depth profiles of $\delta$$^{13}$C-DIC show a decrease between 1993 and 2003, typically of $<$0.2 $\permil$ in the upper 1000m, except in the tropical latitudes (south of 12$\deg$N), where the $\delta$$^{13}$C-DIC decrease is restricted to $\sim$100m. For several depth profiles, especially in the tropics and subtropics, the $\delta$$^{13}$C-DIC decrease was reduced after normalizing for changes in phosphate. The observed $\delta$$^{13}$C-DIC changes will be discussed in terms of natural variability and uptake of anthropogenic CO$_{2}$.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4870 Stable isotopes
DE: 4215 Climate and interannual variability (3309)
DE: 1615 Biogeochemical processes (4805)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting