Sea-to-air fluxes from measurements of the atmospheric gradient of dimethylsulfide and comparison with simultaneous relaxed eddy accumulation measurements

We measured vertical profiles of dimethylsulfide (DMS) in the atmospheric marine boundary layer from R/P FLIP during the 2000 FAIRS cruise. Applying Monin-Obukhov similarity theory to the DMS gradients and simultaneous micrometeorological data, we calculated sea-to-air DMS fluxes for 34 profiles. From the fluxes and measured seawater DMS concentrations, we calculated the waterside gas transfer velocity, kw. Gas transfer velocities from the gradient flux approach are within the range of previous commonly used parameterizations of kw as a function of wind speed but are a factor of 2 smaller than simultaneous determinations of transfer velocity using the relaxed eddy accumulation technique. This is the first field comparison of these different techniques for measuring DMS flux from the ocean; the accuracy of the techniques and possible reasons for the discrepancy are discussed

Fluxes and gas transfer rates of the biogenic trace gas DMS derived from atmospheric gradients

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C08S10, doi:10.1029/2003JC001795.Gas transfer rates were determined from vertical profile measurements of atmospheric dimethylsulfide (DMS) gradients over the equatorial Pacific Ocean obtained during the GasEx-2001 cruise. A quadratic relationship between gas transfer velocity and wind speed was derived from the DMS flux measurements; this relationship was in close agreement with a parameterization derived from relaxed eddy accumulation measurements of DMS over the northeastern Pacific Ocean. However, the GasEx-2001 relationship results in gas transfer rates that are a factor 2 higher than gas transfer rates calculated from a parameterization that is based on coincident eddy correlation measurements of CO2 flux. The measurement precision of both the profiling and eddy correlation techniques applied during GasEx-2001 is comparable; the two gas transfer data sets are in agreement within their uncertainty. Differences in the number of samples and the wind speed range over which CO2 and DMS fluxes were measured are likely causes for the observed discrepancy.Funding for this work came from the Netherlands Organization for Scientific Research (NWO) and from the NOP project 951203: ‘‘Micrometeorology of air/sea fluxes of carbon dioxide. This work was supported by the Global Carbon Cycle project of the NOAA Office of Global Programs grant NA17RJ1223, National Science Foundation grant OCE-9986724, and NSF grant ATM-0120569

Environmental turbulent mixing controls on air-water gas exchange in marine and aquatic systems

Air-water gas transfer influences CO2 and other climatically important trace gas fluxes on regional and global scales, yet the magnitude of the transfer is not well known. Widely used models of gas exchange rates are based on empirical relationships linked to wind speed, even though physical processes other than wind are known to play important roles. Here the first field investigations are described supporting a new mechanistic model based on surface water turbulence that predicts gas exchange for a range of aquatic and marine processes. Findings indicate that the gas transfer rate varies linearly with the turbulent dissipation rate to the equation image power in a range of systems with different types of forcing - in the coastal ocean, in a macro-tidal river estuary, in a large tidal freshwater river, and in a model (i.e., artificial) ocean. These results have important implications for understanding carbon cycling

Climate related shifts in the NCP ecosystem, and consequences for future spatial planning

Een uitgebreide meetinspanning op de Noordzee, in combinatie met wiskundige en statistische modellering, laat zien dat de klimaatveranderingen in de vorm van een verandering in de overheersende windrichting, een toename van de windsnelheid, een toename van de zeewatertemperatuur, als wel als een toenemende CO2 concentratie van de atmosfeer, niet alleen leidt tot een verandering van de samenstelling van het zeewater in de vorm van bijvoorbeeld opgelost anorganisch koolstof en zuurgraad, maar ook tot een, zei het beperkte, verlaging van de productiviteit van op en in de zeebodem levende filterende organismen, die op hun beurt het voedsel zijn van bodembewonende vissen

Dimethylsulfide emissions over the multi-year ice of the western Weddell Sea

This study, conducted in December 2004, is the first to present observations of DMS in a snow pack covering the multi-year sea ice of the western Weddell Sea. The snow layer is important because it is the interface through which DMS needs to be transported in order to be emitted directly from the ice to the overlying atmosphere. High concentrations of DMS, up to 6000 nmol m-3, were found during the first weeks of December but concentrations sharply decline as late spring-early summer progresses. This implies that DMS contained in sea ice is efficiently vented through the snow into the atmosphere. Indeed, field measurements by relaxed eddy accumulation indicate an average release of 11 µmol PMS m-2 d-1 from the ice and snow throughout December

Gradients in dimethylsulfide, dimethylsulfoniopropionate, dimethylsulfoxide, and bacteria near the sea surface

Author Posting. © Inter-Research, 2005. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 295 (2005): 33-42, doi:10.3354/meps295033.Gradients of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), and bacterial numbers and diversity from the surface microlayer to 500 cm depth were assessed in coastal waters surrounding the Martha’s Vineyard Coastal Observatory, Massachusetts, USA. Microlayer samples were collected with a surface skimmer: a partially submerged, rotating glass cylinder (‘drum’) that allows the collection of a thin layer of water by adherence to the drum. A depletion of DMS towards the water surface (10 cm) was found at all sampling days, with largest gradients during rough sea surface conditions. The steep gradients show that gas fluxes and transfer velocities, based on the concentration disequilibrium between the water and the atmosphere, need to be based on near surface gas concentration values. Elevated DMSP, DMSO concentrations and bacterial numbers were found at the sea surface during calm conditions. Although degassing and photo-oxidation on the skimmer will bias the microlayer data, the results indicate stratification of DMSP, DMSO and bacteria during periods of smooth sea surface conditions.We also thank the postdoctoral scholar program at the Woods Hole Oceanographic Institution, with funding provided by the J. Seward Johnson Fund