HR: 0800h
AN: A31B-0054    [Abstracts]
TI: Meridional trends in concentration and hydrogen isotope ratio of atmospheric H$_{2}$
AU: * Rice, A L
EM: arice@ocean.washington.edu
AF: Joint Insitute for the Study of the Atmosphere and Ocean, University of Washington, 4909 25th Ave. NE Box 354235, Seattle, WA 98195-4235 United States
AU: Quay, P
EM: pdquay@u.washington.edu
AF: School of Oceanography, University of Washington, 1492 NE Boat St Box 355351, Seattle, WA 98195-5351 United States
AU: Stutsman, J
EM: johnnys@u.washington.edu
AF: School of Oceanography, University of Washington, 1492 NE Boat St Box 355351, Seattle, WA 98195-5351 United States
AB: Measurements of H$_{2}$ concentration and hydrogen isotope ratio were made on air samples collected on Pacific Ocean transects between Seattle, WA and Antarctica during Nov-Dec, 1998, May-June, 2002, and December-March 2004. Both in situ and grab sample measurements indicate a maximum in H$_{2}$ mixing ratio in the equatorial region near 600ppbv with mixing ratio decreasing poleward to $\sim$540ppbv in the high latitude southern hemisphere and to $\sim$520ppbv in the mid latitude northern hemisphere. Isotopic analyses reveal that this trend in mixing ratio is mirrored by a minimum in $\delta$D-H$_{2}$ in the equatorial region with values near 80$\permil$ (versus VSMOW), increasing poleward to $\sim$150$\permil$ in the high latitude southern hemisphere and to $\sim$125$\permil$ in the mid latitude northern hemisphere. The poleward increase in $\delta$D with decreasing mixing ratio appears to be stronger in gradient in the southern hemisphere than in the north as a result of the increased importance of the OH sink relative to the soil sink. Additionally, the importance of photochemical H$_{2}$ sources, enriched in deuterium, in the southern hemisphere relative to primary sources, depleted in deuterium, contributes to this observed gradient. However, in either hemisphere these data indicate that the poleward increase in $\delta$D with decreasing H$_{2}$ mixing ratio is too large to be due to sink effects and potentially too large to be explained by the distribution of known sources (i.e., photochemical hydrocarbon oxidation and surface sources biomass burning and fossil fuel combustion). Results suggest the presence of a very deuterium enriched source at high latitudes, potentially from stratospheric-tropospheric exchange.
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting