The complex response of Arctic aerosol to sea-ice retreat
The complex response of Arctic aerosol to sea-ice retreat
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DOI：
10.5194/acp-14-7543-2014
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发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Leck, C.
中科院分区：
文献类型：
--
作者：
Browse, J.;Carslaw, K. S.;Leck, C.
夏季北冰洋海冰的消失将导致海洋表面气溶胶和前体气体排放量的大幅增加。有人提出，这些增加的排放将产生大量的气溶胶辐射强迫，主要是气溶胶对云的间接影响。在这里，我们使用一个全球气溶胶微物理模型来研究这些间接强迫的可能性，该模型针对北极夏季云海研究(ASCOS)活动中的气溶胶观测进行了评估，以检查北极云凝结核(CCN)对海冰消退的响应。在夏季冰完全消失的情况下，我们发现在北纬70度以北，海盐、海洋初级有机气溶胶和二甲基硫化物的排放通量分别增加了约10倍、4倍和15倍。然而，CCN的响应较弱，北冰洋中部出现负变化。较弱的反应是由于大范围的层积云对气溶胶的有效清除。在以清扫为主的北极环境中，二甲基硫化物氧化产生的可凝结蒸汽会使颗粒长大，达到可以清除的大小。这一损失不能通过新颗粒的形成得到充分补偿，这是由于海盐和初级油酸排放导致的大冷凝汇抑制了成核。因此，我们的结果表明，气溶胶排放的增加不会通过改变云的微物理和辐射性质来引起气候反馈。
Loss of summertime Arctic sea ice will lead to a large increase in the emission of aerosols and precursor gases from the ocean surface. It has been suggested that these enhanced emissions will exert substantial aerosol radiative forcings, dominated by the indirect effect of aerosol on clouds. Here, we investigate the potential for these indirect forcings using a global aerosol microphysics model evaluated against aerosol observations from the Arctic Summer Cloud Ocean Study (ASCOS) campaign to examine the response of Arctic cloud condensation nuclei (CCN) to sea-ice retreat. In response to a complete loss of summer ice, we find that north of 70 degrees N emission fluxes of sea salt, marine primary organic aerosol (OA) and dimethyl sulfide increase by a factor of similar to 10, similar to 4 and similar to 15 respectively. However, the CCN response is weak, with negative changes over the central Arctic Ocean. The weak response is due to the efficient scavenging of aerosol by extensive drizzling stratocumulus clouds. In the scavenging-dominated Arctic environment, the production of condensable vapour from oxidation of dimethyl sulfide grows particles to sizes where they can be scavenged. This loss is not sufficiently compensated by new particle formation, due to the suppression of nucleation by the large condensation sink resulting from sea-salt and primary OA emissions. Thus, our results suggest that increased aerosol emissions will not cause a climate feedback through changes in cloud microphysical and radiative properties.