Atmospheric DMS and its role in new aerosol formation

二甲基硫化物(DMS)氧化及其在产生可能影响云的形成、持久性和反照率的新气溶胶方面的作用是气候研究的一个关键领域。在北极和高纬度地区尤其如此，因为由于辐射强迫，最终产生大气DMS的表层海洋预计将经历比赤道更大的温度变化。由于表层水温的变化，海洋表层水中二甲基硫的梯度较高，通常预计会增加大气中二甲基硫的混合比率，但海-气交换的动态也是需要考虑的因素。DMS的海-气交换通常随着海面粗糙度的增加而增加，并表示为风速和海面温度的经验函数。然而，与粗糙度无关的海洋表面特征被假定为促进参与北极新气溶胶形成的化合物的海-气交换(Leck和Bigg，2005)。许多研究使用地表水中DMS的测量来估计DMS通量和固定的甲烷磺酸(MSA)到生物硫酸盐的分支比来评估DMS气溶胶硫酸盐形成对云凝结核(CCN)的影响。新的研究表明，这样的估计可能严重低估了海洋到空气中DMS的通量，和/或在中高纬度地区，特别是在春季和夏季，DMS形成二氧化硫和硫酸盐的氧化途径被低估了。在这项研究中，将利用DMS氧化产物硫酸盐气溶胶、二氧化硫和MSA的同位素特征来评估北极和北太平洋区域尺度的DMS通量和DMS氧化途径。将通过一系列合作和独立的现场研究来评估DMS氧化的趋势，以提供对DMS寿命、其氧化途径以及其形成新的气溶胶硫酸盐的潜力的定量估计。

Dimethylsulphide (DMS) oxidation and its role in generating new aerosols that have the potential to influence cloud formation, persistence and albedo is a key area of study for climate research. This is particularly true in the Arctic and at high latitudes as the surface oceans that ultimately generate atmospheric DMS are expected to experience more temperature variation than at the equator due to radiative forcing. Higher DMS gradients in ocean surface waters as a result of changing in surface water temperatures are generally expected to increase DMS mixing ratios in the atmosphere but the dynamics of sea-air exchange are also factors that need to be considered. Sea-air exchange of DMS typically increases with sea surface roughness and is expressed as an empirical function of wind speed and sea surface temperature. However, ocean surface characteristics not related to roughness are postulated to promote sea-air exchange for compounds participating in new aerosol formation in the Arctic (Leck and Bigg, 2005). Many studies use DMS measurements in surface waters to estimate DMS flux and a fixed branching ratio for methanesulphonic acid (MSA) to biogenic sulphate to assess the impact of DMS aerosol sulphate formation on cloud condensation nuclei (CCN). New research shows such estimates may grossly under-represent sea to air DMS flux, and/or the DMS oxidation pathways forming sulphur dioxide and sulphate are underestimated at mid to high latitudes particularly during spring and summer. In this study, the isotope characteristics of sulphate aerosols, sulphur dioxide, and MSA, products of DMS oxidation will be used to assess regional scale DMS flux and DMS oxidation pathways in the Arctic and over the North Pacific. Trends in DMS oxidation will be assessed through a series of collaborative and independent field studies to provide quantitative estimates of DMS lifetime, its oxidation pathways, and its potential for forming new aerosol sulphate.