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，或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可以是形成云滴的云凝聚核(CCN)，但最近才表明，SSA也可以是形成冰晶的冰核粒子(INP)的来源，这取决于其化学成分和表面形状。北极云在气候模型中的表现不佳，部分原因是缺乏对北极高海拔地区天然气溶胶来源和成核能力的了解。例如，气溶胶模式目前没有捕捉到在高纬度观测到的北极冬季/春季的气溶胶最大值。最近的实地活动首次提供了证据，证明SSA的假设来源是海冰上方的咸雪(BSN)。在暴风雨期间，含盐的雪被升华到空气中，并经过升华产生SSA。SSA海冰的额外但次要来源是霜花和开放导线。海冰上SSA的这种新来源对SSA的辐射和云的影响尚不清楚。然而，需要对自然气溶胶过程和气候相互作用有一个定量的了解，以提供基准，以评估到达北极的人为污染，并评价缓解措施的成功。因此，我们建议确定SSA的来源、命运和与海冰和其他海冰来源上方吹雪有关的对北极气候的潜在影响。为此，我们寻求资金，以参加为期一年的北极气候研究多学科漂移观测站(MOSAIC)，以观测北冰洋中部所有季节的气溶胶过程。建议对海冰和船上的“FS Polarstein”进行的测量包括颗粒大小和浓度(亚微米到雪的颗粒大小)、INP浓度以及使用气溶胶过滤器的一系列化学性质。对海冰、盐水、霜花上的雪进行采样将限制当地SSA的来源。系留气球的发射将提供有关海冰表面附近形成的颗粒在升空到可能形成云的高度时的命运的信息。

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.