![]() ![]() Meanwhile, the aged aerosol regime in this region may have different sources and aerosol properties compared with more well-studied anthropogenic emission hotspot regions. The vast expanse of the Indian Ocean makes the cumulative climate effects in this region comparably large. Given its mean lifetime of around a week, the climate impact of BC is largely regional, and vast emissions from hotspot regions like South Asia and Africa may perturb both regional climate and the South Asian monsoon system over extensive scales of the northern Indian Ocean, with potentially devastating effects on the regions’ agriculture and freshwater supply.ĭespite its relatively short lifetime, BC is still ubiquitously observed far afield in the wider receptor regions of global emission hotspot regions such as those of South Asia, China, and Africa ( Fig. The climate effects of BC remain highly uncertain, reflecting poorly constrained emission sources, optical properties, atmospheric transport, and aerosol–cloud interactions ( 2– 4). Furthermore, BC is also a cloud condensation nuclei (CCN), making BC–cloud interactions an additional modulator of climate impact, potentially countering the direct effects ( 2). Within the chemically complex aerosol mixture, black carbon (BC) plays an important role as it is likely the most significant component that absorbs sunlight and thereby contributes to direct climate warming-in contrast to the overall cooling effect of aerosols. 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.Īerosols remain one of the largest uncertainties in our current understanding of Earth’s climate system ( 1). The BC mass-absorption cross-section for this regime is 7.6 ± 2.6 m 2/g, with higher values during savanna fire input. Combining carbon-14 with carbon-13 reveals the impact of African savanna burning, which occasionally approach 50% (48 ± 9%) of the total BC loadings. Carbon-14 data show a highly variable yet largely fossil (65 ± 15%) source mixture. 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. Uncertain contributions from various natural and anthropogenic sources impede our understanding. ![]() Effects of aerosols such as black carbon (BC) on climate and buildup of the monsoon over the Indian Ocean are insufficiently quantified. ![]()
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