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中的作用是气候研究的一个关键研究领域。这在北极和高纬度地区尤其如此，因为由于辐射强迫，预计最终产生大气DMS的表层海洋将比赤道经历更大的温度变化。一般认为，由于地表水温度的变化，海洋表层水中的DMS梯度增大，会增加大气中DMS的混合比，但海气交换的动力学也是需要考虑的因素。DMS海气交换随海面粗糙度的增加而增加，并表现为风速和海面温度的经验函数。然而，假定与粗糙度无关的海洋表面特征促进了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的DMS测量来估计DMS通量和固定的甲烷磺酸（MSA）与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，这种估计可能严重低估了海洋到空气的DMS通量，和/或形成二氧化硫和硫酸盐的DMS氧化途径在中高纬度地区被低估，特别是在春季和夏季。在本研究中，硫酸盐气溶胶、二氧化硫和DMS氧化产物MSA的同位素特征将用于评估北极和北太平洋地区区域尺度DMS通量和DMS氧化途径。DMS氧化的趋势将通过一系列合作和独立的实地研究进行评估，以提供DMS寿命、氧化途径及其形成新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.