Maldives Climate Observatory at Hanimaadhoo, Maldives Meteorological Services, H. Dh. Hanimaadhoo 02020, Republic of Maldives.
Divecha Centre for Climate Change, Indian Institute of Science, Bangalore 560012, India.
Proc Natl Acad Sci U S A. 2023 Feb 21;120(8):e2210005120. doi: 10.1073/pnas.2210005120. Epub 2023 Feb 13.
Effects of aerosols such as black carbon (BC) on climate and buildup of the monsoon over the Indian Ocean are insufficiently quantified. Uncertain contributions from various natural and anthropogenic sources impede our understanding. Here, we use observations over 5 y of BC and its isotopes at a remote island observatory in northern Indian Ocean to constrain loadings and sources during little-studied monsoon season. Carbon-14 data show a highly variable yet largely fossil (65 ± 15%) source mixture. Combining carbon-14 with carbon-13 reveals the impact of African savanna burning, which occasionally approach 50% (48 ± 9%) of the total BC loadings. The BC mass-absorption cross-section for this regime is 7.6 ± 2.6 m/g, with higher values during savanna fire input. Taken together, the combustion sources, longevity, and optical properties of BC aerosols over summertime Indian Ocean are different than the more-studied winter aerosol, with implications for chemical transport and climate model simulations of the Indian monsoon.
气溶胶（如黑碳）对气候的影响以及对印度洋季风的积累作用还没有得到充分的量化。各种自然和人为来源的不确定贡献阻碍了我们的理解。在这里，我们利用在印度洋北部一个偏远岛屿观测站进行的为期 5 年的黑碳及其同位素观测，来限制季风季节中负荷和来源。碳-14 数据显示出一种高度可变但主要是化石的（65±15%）源混合物。将碳-14 与碳-13 结合起来，可以揭示非洲热带稀树草原燃烧的影响，这种燃烧偶尔会接近总黑碳负荷的 50%（48±9%）。在这一区域，BC 的质量吸收消光截面为 7.6±2.6 m/g，在热带稀树草原火灾输入期间，该值更高。总的来说，与研究更为充分的冬季气溶胶相比，夏季印度洋上的 BC 气溶胶的燃烧源、寿命和光学特性有所不同，这对印度季风的化学输运和气候模型模拟有影响。
