Marine Fresh Carbon Pool Dominates Summer Carbonaceous Aerosols Over Arctic Ocean.

The source of marine carbonaceous aerosols is crucial to determine as it provides information about the ocean‐cloud‐climate relationship and the carbon cycle. However, contribution of different marine organic pools to marine primary organic aerosols remains controversial and this will lead to uncertainties in climate models. Here, we report the stable carbon isotopes and carbonaceous fraction of marine aerosols, measured during three summer Arctic cruises (33°N–85°N, July‐September, 2014–2018). By comparing the stable carbon isotopic signatures of seawater and aerosols in the Arctic Ocean, we found that the marine fresh carbon pool had a depleted isotopic signature, contributing 80 ± 12% of the carbonaceous fraction. Both in 2016 and 2018, the aerosol carbon isotopes in the Arctic Ocean were significantly higher than those in 2014. Increased productivity in the Arctic Ocean may dominate the increase of stable carbon isotope in the marine fresh carbon pool on an annual scale. Our research highlights the important contribution of fresh marine carbon pool to marine carbonaceous aerosols in response to marine ecosystem change under Arctic warming. Plain Language Summary: The source of marine carbonaceous aerosols is crucial to determine as it provides information about climate change. The Arctic has received widespread attention due to the rapid warming of recent years. Here, we report the stable carbon isotopes and carbonaceous fraction of marine aerosols, measured during three summer Arctic cruises. Stable carbon isotopes can be effective in probing the origin of marine aerosols. By comparing the stable carbon isotopic signatures of seawater and aerosols in the Arctic Ocean, we found the same isotopic signature between aerosols and sea surface particulate organic carbon. This means that the fresh marine carbon pool represented by marine particulate organic carbon may be an important and neglected pool of carbon and dominates the Arctic Ocean carbonaceous aerosol. On multi‐year scales, increased productivity due to Arctic warming may be reflected in changes in aerosol carbon isotopes. This research highlights the important contribution of fresh marine carbon pool to marine carbonaceous aerosols in response to marine ecosystem change under Arctic warming. Key Points: Stable carbon isotope of aerosol during three Arctic cruises are reportedFresh carbon pool contributing 80 ± 12% of Arctic Ocean carbonaceous aerosolArctic warming leads to higher carbon isotope in summer Arctic Ocean aerosols [ABSTRACT FROM AUTHOR]

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