Measurement report: Validation of multi-satellite remote sensing products and potential source apportionment of BrO and IO in the Arctic using ship-based DOAS

Atmospheric reactive halogen species (RHS) in the Arctic are critical to polar sea-atmosphere interactions and global chemical cycles. Here, we used ship-based MAX-DOAS during China’s 12th Arctic Scientific Expedition to conduct spatial observations of NO2, HCHO, BrO, and IO along the Shanghai-Arctic round-trip cruise, aiming to validate satellite data’s polar applicability and identify RHS source regions and driving mechanisms. Ship-based measurements were compared with TROPOMI, GEMS, and GOME-2 satellite products, showing good agreement (all correlation coefficients > 0.6). BrO concentrations showed a significant positive correlation with air mass-sea ice contact duration. The high-probability source regions were identified in western Greenland, the seas north of North America, and the Arctic sea ice edge zone, confirming that sea ice-related photochemical processes serve as the primary formation mechanism of BrO. IO showed a strong positive correlation with chlorophyll-a, with biogenic sources in phytoplankton-enriched regions (Bering Strait, southern Greenland, coastal North Atlantic), verifying marine biological processes as key to IO production. BrO and IO exhibited distinct spatial distributions in their source regions (corresponding to sea-ice-covered areas and mid-to-low latitude coastal biologically active zones, respectively). However, a moderate correlation (R=0.5) was observed between them in the sea ice edge zone, attributable to their shared "ice-sea-atmosphere" exchange interfaces. This study provides critical in-situ validation for Arctic satellite pollutant data, clarifies the sea ice-coupled formation mechanism of BrO and the biogenic-driven formation mechanism of IO, and offers data support for polar atmospheric chemistry model optimization and global climate assessments.