| 英文摘要: | Clouds play a key role in modulating surface temperature. Their formation is influenced, in part, by the availability of cloud condensation nuclei (CCN) — small particles upon which water vapour can condense. In the Arctic, where rapid climatic change has been observed, the pristine summertime atmosphere is particularly sensitive to CCN number. Betty Croft from Dalhousie University, Canada, and colleagues examine a previously unquantified biological–atmosphere coupling; the impact of seabird colony guano on cloud properties in the Arctic. Observations from Nunavut, Canada are used alongside simulations from a state-of-the-art chemistry–climate model that incorporates an active particle formation scheme. The authors reveal migratory seabirds as a key summertime source of CCN, linked to ammonia emissions from guano decomposition and subsequent particle formation. Simulations indicate that these particles spread throughout the Arctic where they grow and modify cloud characteristics, which can increase cloud albedo. This guano-related CCN effect cools the Arctic by −0.5 Wm−2, but up to −1 Wm−2 near the largest colonies. These natural biochemical interactions represent a regionally important process given substantial anthropogenic warming in the Arctic. |