HR: 0800h
AN: A51C-0593    [Abstracts]
TI: Development of Regional and Global Climatologies of Surface Ocean Bromoform Concentrations
AU: * Palmer, C J
EM: plmcar003@uct.ac.za
AF: University of Cape Town, Rondebosch, Cape Town, 7701, South Africa
AU: Reason, C J
EM: cjr@egs.uct.ac.za
AF: University of Cape Town, Rondebosch, Cape Town, 7701, South Africa
AB: Bromoform is produced in the oceans by phytoplankton and seaweeds (macroalgae). This production is thought to result in supersaturation of most of the surface oceans and therefore a net flux of bromoform to the marine boundary layer (MBL). In the MBL bromoform may photolyse resulting in bromine radicals, which catalytically destroy ozone. Bromoform may also persist long enough to perturb oxidative photochemistry in the free troposphere and stratosphere. An accurate assessment of the magnitude of the oceanic source of bromoform is therefore of great interest. Recent studies [Yang et al., 2005; Warwick et al., 2006] have developed approaches that model bromoform concentrations in the atmosphere. However these models are limited by poorly constrained estimations of the oceanic source; specifically very low skill in resolving spatial and temporal distribution. Here we present a climatological approach to parameterizing the distribution of bromoform in the surface ocean. Approximately 15,000 air and surface seawater concentration measurements from 52 previously published studies were collated and tagged with time, date and location information. For each one of these data points remote sensed data for a variety of relevant variables, including sea surface temperature, chlorophyll-a and wind speed were collated and assigned. These remotely sensed variables were used to parameterize the sources and sinks of bromoform in the surface ocean. This facilitated the development of a model formula for sea surface concentrations of bromoform. The results of regional parameterization experiments show that this method adequately captures the variability of sea surface bromoform concentrations; on a regional scale the R² correlation co-efficient for a plot of the observed against modeled bromoform concentration ranged from 0.48 (Southern Ocean) - 0.52 (Tropics), with P values of less than 0.001. Sea-air fluxes were calculated from the climatology output, satellite wind speed and average bromoform air concentration, using the parameterization of Wanninkhof [1992]. These results show strongest fluxes in tropical regions and a global sea-air flux comparable to recent estimates. The temporal and spatial resolution that this approach provides may facilitate improved modeling of bromoform in the atmosphere. Furthermore this approach may allow tentative predictions of bromoform concentrations in a changing climate, or in regions where no data is available.
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0330 Geochemical cycles (1030)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting