Abstract. A database of 15,617 point measurements of dimethylsulfide (DMS) in surface waters along with lesser amounts of data for aqueous and particulate dirhethylsulfoniopropionate concentration, chlorophyll concentration, sea surface salinity and temperature, and wind speed has been assembled. The database was processed to create a series of climatological annual and monthly 1øxl ø latitude-longitude squares of data. The results were compared to published fields of geophysical and biological parameters. No significant correlation was found between DMS and these parameters, and no simple algorithm could be found to create monthly fields of sea surface DMS concentration based on these parameters. Instead, an annual map of sea surface DMS was produced using an algorithm similar to that employed by Conkright et al. [1994]. In this approach, a first-guess field of DMS sea surface concentration measurements is created and then a correction to this field is generated based on actual measurements. Monthly sea surface grids of DMS were obtained using a similar scheme, but the sparsity of DMS measurements made the method difficult to implement. A scheme was used which projected actual data into months of the year where no data were otherwise present.

Carbonaceous aerosols cause strong atmospheric heating and large surface cooling that is as important to South Asian climate forcing as greenhouse gases, yet the aerosol sources are poorly understood. Emission inventory models suggest that biofuel burning accounts for 50 to 90% of emissions, whereas the elemental composition of ambient aerosols points to fossil fuel combustion. We used radiocarbon measurements of winter monsoon aerosols from western India and the Indian Ocean to determine that biomass combustion produced two-thirds of the bulk carbonaceous aerosols, as well as one-half and two-thirds of two black carbon subfractions, respectively. These constraints show that both biomass combustion (such as residential cooking and agricultural burning) and fossil fuel combustion should be targeted to mitigate climate effects and improve air quality.

Marine microgels play an important role in regulating ocean basinscale biogeochemical dynamics. In this paper, we demonstrate that, in the high Arctic, marine gels with unique physicochemical characteristics originate in the organic material produced by ice algae and/or phytoplankton in the surface water. The polymers in this dissolved organic pool assembled faster and with higher microgel yields than at other latitudes. The reversible phase transitions shown by these Arctic marine gels, as a function of pH, dimethylsulfide, and dimethylsulfoniopropionate concentrations, stimulate the gels to attain sizes below 1 μm in diameter. These marine gels were identified with an antibody probe specific toward material from the surface waters, sized, and quantified in airborne aerosol, fog, and cloud water, strongly suggesting that they dominate the available cloud condensation nuclei number population in the high Arctic (north of 80°N) during the summer season. Knowledge about emergent properties of marine gels provides important new insights into the processes controlling cloud formation and radiative forcing, and links the biology at the ocean surface with cloud properties and climate over the central Arctic Ocean and, probably, all oceans.air-sea exchange | immunological probes | Melosira arctica O ur limited knowledge about cloud radiative processes remains a major weakness in our understanding of the climate system and consequently in developing accurate climate projections (1). This is especially true for low-level Arctic clouds, which play a key role in regulating surface energy fluxes, affecting the freezing and melting of sea ice, when the climate is changing faster in the Arctic than at any other place on earth. The radiative or reflective (albedo) properties of clouds strongly depend on the number concentration of aerosol particles available for uptake or condensation of water vapor at a given water supersaturation. Such particles are known as cloud condensation nuclei (CCN), and their activation and growth (2) depend on the equilibrium thermodynamics by which water vapor condenses on CCN and forms a liquid cloud drop. In the high Arctic, the aerosol-cloud-radiation relationship is more complex than elsewhere, and for most of the year, the low-level clouds constitute a warming factor for climate rather than cooling (3). In summer, this is due to the semipermanent ice cover, which raises the albedo of the surface, and to the clean Arctic air (4), which decreases the albedo of the low-level clouds. Small changes in either factor are very important to the heat transfer to the ice and the subsequent summertime ice-melt. The high Arctic CCN originate in the open leads in the pack ice and from sources along the marginal ice edge; they are formed mostly by aggregates of organic material, presumably of marine origin (5-7).Marine polymer microgels are 3D polymer hydrogel networks that result from the spontaneous assembly/dispersion equilibrium of free biopolymers in the dissolved organic matter (DOM) pool. Microgels fo...