Emission patterns and trends of primary marine organic aerosol in the Arctic

Primary marine organic aerosol (PMOA) is a significant contributor to aerosol concentrations in remote oceanic regions, influencing aerosol-cloud-climate interactions. In the Arctic, sea ice retreat and summer ice loss are key drivers of potential increases in marine aerosol emissions. This study uses an extended version of the aerosol-climate model ECHAM6.3-HAM2.3 to investigate the emission patterns and trends of primary marine organic aerosol in the Arctic from 1990 to 2019 in large detail, considering changing climate and ice conditions. Using the offline results of the biogeochemistry model FESOM2.1-REcoM3, three aerosol-relevant biomolecule groups - polysaccharides (PCHO), amino acids (DCAA), and polar lipids (PL) - are modelled. Their atmospheric transfer is parameterized with OCEANFILMS, which was implemented into the aerosol-climate model ECHAM6.3-HAM2.3 to advance the marine emission scheme. Of the modelled organic groups, PCHO is most abundant in seawater, while PL dominates aerosol particles due to its higher air-seawater affinity. Seasonal variations in both the ocean and aerosol concentrations are pronounced, peaking between May and June, then gradually decreasing by late summer. The modelled PMOA seasonal patterns show reasonable agreement with ground-based measurements, considering the uncertainties in model assumptions and observations. Regional differences within the Arctic are evident in the initiation of biomolecule production in seawater and aerosol emissions. Long-term trends in Arctic PMOA emissions, analysed in this study, reveal a strong dependence on sea ice changes. Over the 30-year period, emissions have increased by at least 24%, with variations among biomolecules and regions. PCHO shows the most pronounced trend.