Measurement report: Summertime fluorescence characteristics of atmospheric water-soluble organic carbon in the marine boundary layer of the western Arctic Ocean

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Jung, Jinyoung, Miyazaki, Yuzo, Hur, Jin, Lee, Yun Kyung, Jeon, Mi Hae, Lee, Youngju, Cho, Kyoung-Ho, Chung, Hyun Young, Kim, Kitae, Choi, Jung-Ok, Lalande, Catherine, Kim, Joo-Hong, Choi, Taejin, Yoon, Young Jun, Yang, Eun Jin, Kang, Sung-Ho
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Arctic; Arctic Ocean; Sea ice; ice covered areas
• Online Access: https://doi.org/10.5194/acp-23-4663-2023; https://noa.gwlb.de/receive/cop_mods_00066022; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00064524/acp-23-4663-2023.pdf; https://acp.copernicus.org/articles/23/4663/2023/acp-23-4663-2023.pdf

Accelerated warming and a decline in sea ice coverage in the summertime Arctic Ocean can significantly affect the emissions of marine organic aerosols and biogenic volatile organic compounds. However, how these changes affect the characteristics of atmospheric water-soluble organic carbon (WSOC), which plays an important role in the climate system, remains unclear. Thus, to improve our understanding of WSOC characteristics in the rapidly changing Arctic Ocean, including its summertime fluorescence characteristics, we simultaneously measured atmospheric concentrations of ionic species and WSOC, a fluorescence excitation–emission matrix coupled with parallel factor (EEM-PARAFAC) analysis of WSOC, and marine biological parameters in surface seawaters of the western Arctic Ocean during the summer of 2016. WSOC was predominantly present as fine-mode aerosols (diameter <2.5 µm, median =92 %), with the mean concentration being higher in the coastal water areas (462±130 ngC m−3) than in the sea-ice-covered areas (242±88.4 ngC m−3). Moreover, the WSOC in the fine-mode aerosols was positively correlated with the methanesulfonic acid in the fine-mode aerosol samples collected over the sea-ice-covered areas (r=0.88, p<0.01, n=10), suggesting high rates of sea–air gas exchange and emissions of aerosol precursor gases due to sea ice retreat and increasingly available solar radiation during the Arctic summer. Two fluorescent components, humic-like C1 and protein-like C2, were identified by the PARAFAC modeling of fine-mode atmospheric WSOC. The two components varied regionally between coastal and sea-ice-covered areas, with low and high fluorescence intensities observed over the coastal areas and the sea-ice-covered areas, respectively. Further, the humification index of WSOC was correlated with the fluorescence intensity ratio of the humic-like C1 / protein-like C2 (r=0.89, p<0.01) and the WSOC concentration in the fine-mode aerosols (r=0.66, p<0.05), with the highest values observed in the coastal areas. ...