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.

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...

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Oceanic dimethylsulfide (DMS) emissions to the atmosphere are potentially important to the Earth's radiative balance. Since these emissions are driven by the surface seawater concentration of DMS, it is important to understand the processes controlling the cycling of sulfur in surface seawater. During the third Pacific Sulfur/Stratus Investigation (PSI-3, April 1991) we measured the major sulfur reservoirs (total organic sulfur, total low molecular weight organic sulfur, ester sulfate, protein sulfur, dimethylsulfoniopropionate (DMSP), DMS, dimethylsulfoxide) and quantified many of the processes that cycle sulfur through the upper water column (sulfate assimilation, DMSP consumption, DMS production and consumption, air-sea exchange of DMS, loss of organic sulfur by particulate sinking). Under conditions of low plankton biomass (<0.4 gg/L chlorophyll a) and high nutrient concentrations (>8 tam nitrate), 250 km off the Washington State coast, DMSP and DMS were 22% and 0.9%, respectively, of the total particulate organic sulfur pool. DMS production from the enzymatic cleavage of DMSP accounted for 29% of the total sulfate assimilation. However, only 0.3% of sulfate-S assimilated was released to the atmosphere. From these data it is evident that air-sea exchange is currently only a minor sink in the seawater sulfur cycle and thus there is the potential for much higher DMS emissions under different climatic conditions. Introduction Oceanic dimethylsulfide (DMS) is currently thought to be the major natural source of sulfur to the atmosphere [Bates et al., 1992; Spiro et al., 1992]. Once in the atmosphere, DMS is oxidized to produce aerosol particles which affect the acidbase chemistry of the atmosphere [Charlson and Rodhe, 1982] and the radiative properties of marine stratus clouds [Charlson et al., 1987; Falkowski et al., 1992]. This latter effect is calculated to have a major impact on the Earth's radiative balance and hence its climate [Charlson et al., 1987]. The starting point in the marine atmospheric sulfur cycle is the air-sea exchange of DMS which is a function of the gas i NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington. transfer velocity and surface seawater DMS concentration. The gas transfer velocity is controlled primarily by surface turbulence, seawater temperature and gas diffusivity and can be modeled as a function of wind speed for various trace gases [Liss and Merlivat, 1986; Wanninkhof, 1992]. The different T. S. Bates, NOAA/Pacific Marine

The simulated PAR and PP increases mainly occur in the seasonally and permanently ice-covered Arctic Ocean. In addition to increasing PAR, the decline in sea ice tends to increase the nutrient availability in the euphotic zone by enhancing air-sea momentum transfer, leading to strengthened upwelling and mixing in the water column and therefore increased nutrient input into the upper ocean layers from below. The increasing nutrient availability also contributes to the increase in the simulated PP, even though significant surface nutrient drawdown in summer is simulated. In conjunction with increasing surface absorption of solar radiation and rising surface air temperature, the increasing surface water temperature in the Arctic Ocean peripheral seas further contributes to the increase in PP. As PP has increased, so has the simulated biomass of phytoplankton and zooplankton.

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