Sea Salt Aerosol above Arctic Sea Ice - sources, processes and climate impacts (SSAASI-CLIM)

海盐气溶胶（SSA）可能通过辐射散射直接影响区域气候，也可能通过其作为云形成粒子的作用间接影响区域气候。虽然众所周知，SSA可以是云凝结核（CCN）形成云滴，但直到最近才表明，SSA也可以是形成冰晶的冰核粒子（INP）的来源，这取决于它的化学成分和表面形状。北极云在气候模式中表现不佳，部分原因是对北极高纬度地区天然气溶胶的来源和成核能力缺乏了解。例如，气溶胶模式目前没有捕捉到在高纬度地区观测到的北极冬季/春季气溶胶最大值。最近的野外活动提供了第一个证据，证明海面上的咸味吹雪（BSn）是SSA的假设来源。在风暴期间，含盐雪上升到空气中，并经过升华产生SSA。其他但较小的SSA海冰来源是霜花和开放的引线。海冰上这种新的SSA源对SSA辐射和云的影响尚不清楚。但是，需要对自然气溶胶过程和气候相互作用有定量的了解，以便为评估到达北极的人为污染和评价缓解措施的成功与否提供一个基线。因此，我们建议确定与海冰上吹雪和其他海冰源相关的SSA来源、命运和对北极气候的潜在影响。为此，我们寻求资金参加为期一年的北极气候研究多学科漂流观测站（MOSAiC），以观察北冰洋中部各个季节的气溶胶过程。拟议的海冰测量和船上的“FS北极星”包括颗粒大小和浓度（亚微米到雪颗粒大小），INP浓度，以及使用气溶胶过滤器的一系列化学性质。海冰上的雪、盐水、霜花的采样将限制SSA的局部来源。系留气球的发射将提供海冰表面附近形成的粒子的命运信息，因为它们被升到可能形成云的高度。

Sea salt aerosol (SSA) may influence regional climate directly through scattering of radiation or indirectly via its role as cloud-forming particles. While it is well known that SSA can be cloud condensation nuclei (CCN) forming cloud droplets, it has been shown only recently that SSA can also be a source of ice nucleating particles (INP) forming ice crystals, depending on its chemical composition and surface shape. Arctic clouds are poorly represented in climate models, which is partly due to a lack of understanding of source and nucleating capability of natural aerosol in the high Arctic. Aerosol models for example do currently not capture aerosol maxima in the Arctic winter/spring observed at high latitudes. Recent field campaigns provide first evidence of a hypothesized source of SSA from salty blowing snow (BSn) above sea ice. During storms salty snow gets lofted into the air and undergoes sublimation to generate SSA. Additional but minor SSA sea ice sources are frost flowers and open leads. The impact on radiation and clouds of SSA from this new source of SSA above sea ice is not known. However, a quantitative understanding of natural aerosol processes and climate interactions is needed to provide a baseline against which to assess anthropogenic pollution reaching the Arctic and evaluate the success of mitigation measures. We therefore propose to determine the SSA source, fate and potential impact on Arctic climate associated with blowing snow above sea ice and other sea ice sources. To do this we seek funding to participate in the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) to observe aerosol processes in the central Arctic ocean throughout all seasons. Proposed measurements on the sea ice and on-board "FS Polarstern" include particle size and concentration (sub-micron to snow particle size), INP concentrations, and a range of chemical properties using aerosol filters. Sampling of snow on sea ice, brine, frost flowers will constrain the local source of SSA. Tethered balloon launches will yield information on the fate of particles formed near the sea ice surface as they get lofted to heights where clouds may form.