Evidence of a Benthic Source of DMS to the Atmosphere in the California Current Upwelling System
Abstract
The reduced gas, dimethylsulfide (DMS), is an important agent in the global sulfur cycle ferrying the vital element from the ocean, where it is abundant as sulfate, to the continents where it is often a limiting nutrient. Rapid atmospheric oxidation of DMS renders sulfuric and methylsulfonic acids that can strongly influence the abundance of cloud condensation nuclei, thereby regulating the Earth's climate. Data from a pilot study along the shore at Bodega Bay, California exhibited considerable variability, with concentrations ranging from 30- 1,300 pptv over the course of several days during onshore flow. The largest of these concentrations could thus deliver upwards of 4 μg m^{-3{ of sulfate to the fine aerosols of the region. The data further reveal a surprisingly direct relationship between the atmospheric DMS levels and the local oceanic upwelling strength, the square root of the wind speed, and the reciprocal of the boundary layer height. From scalar budget considerations it is shown that the functional relationship is indicative of a rapid advective steady state controlled by a strong nearshore source. The dependence on upwelling strength is argued to imply that much of the DMS originates from the organic-rich sediments along the continental shelf, a source completely unique from the conventional planktonic origins of the surface ocean. We conclude that the coastal DMS represents a heretofore unexplored biogeochemical connection between the microbial communities that reside in these shallow, anaerobic marine sediments and the atmosphere, one whose source strength could significantly increase under the influence of global climate change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMOS52C..05F
- Keywords:
-
- 0312 Air/sea constituent fluxes (3339;
- 4504);
- 0315 Biosphere/atmosphere interactions (0426;
- 1610);
- 0442 Estuarine and nearshore processes (4235);
- 4805 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 1615;
- 4820 Gases