Drivers controlling black carbon temporal variability in the Arctic lower troposphere

Abstract

Abstract. Black carbon (BC) is a short-lived climate forcer affecting Arctic climate through multiple mechanisms, which vary substantially from winter to summer. Several models still fail in reproducing BC seasonal variability, limiting the ability to fully describe BC climate implications. This study aims at gaining insights into the mechanisms controlling BC transport from lower latitudes to the Arctic lower troposphere. Here we investigate the drivers controlling black carbon daily and seasonal variability in the Arctic using Generalized Additive Models (GAM). We analysed equivalent black carbon (eBC) concentration measured at the Gruvebadet Atmospheric Laboratory (GAL - Svalbard archipelago) from March 2018 to December 2021. The eBC showed a marked seasonality with higher values in winter and early spring. The eBC concentration averaged 22 ± 20 ng m-3 in the cold season (November–April) and 11 ± 11 ng m-3 in the warm season (May–October). The seasonal and interannual variability was mainly modulated by the efficiency of wet scavenging removal during transport towards the higher latitudes. Conversely, the short-term variability was controlled by boundary layer dynamics, local-scale, and synoptic-scale circulation patterns. During both the cold and the warm season, the transport of air masses from western Europe and northern Russia was an effective pathway for the convey of pollution to the European Arctic. Finally, in the warm season we observed a link between the intrusion of warm air from lower latitudes and the increase in eBC concentration. Changes in synoptic scale circulation system and precipitation rate in the northern hemisphere, linked to climate change, are expected to modify BC burden in the Arctic.