Table 1. Fraction of BCA in the Arctic, mass flux of black carbon aerosol (BCA) to the Arctic, and the contribution of lows and frontal systems (LF) to the mass flux.

Horizontal resolution (km)	56	14	3.5
Ratio of column BCA mass concentration in the Arctic to global column BCA mass concentration (%)	1.0	2.7	4.2
Mass flux of column BCA to the Arctic (kg/s)	8.15	27.66	35.55
Ratio of mass flux by LF to total mass flux (%)	55.95	57.63	58.17

Ratio of column black carbon aerosol (BCA) mass concentration in the Arctic to global column BCA mass concentration; (column BCA accumulated north of 60°N)/(globally accumulated column BCA), and zonally accumulated northward mass flux of column BCA across 60°N averaged during the final 10 days of the simulation. The calculation of mass flux is described in the Supplementary Information. “LF” means lows and frontal systems.