Influence of sea ice on sulfate aerosol budgets in Antarctic Regions with distinct climate conditions

Abstract

Sulfate (SO₄²⁻) is an essential constituent of aerosols that play an important role in regulating global climate. Over the past decades, polar sea-ice cover changed significantly, potentially influencing the atmospheric budget of SO₄²⁻. However, limited research has been conducted to quantify the effects of sea ice on atmospheric SO₄²⁻ over different times and regions. Here, we report the SO₄²⁻/Na⁺ mass ratios of aerosols and precipitation samples collected in coastal East Antarctica and the Antarctic Peninsula during 2016–2022. The SO₄²⁻/Na⁺ mass ratios at both sites show similar seasonal trends; aerosols display higher ratios than precipitation in summer, with no significant difference in winter, possibly due to precipitation preferentially removing coarse-mode aerosols. The percentage of air mass travelling time over sea ice (P-Time) is positively correlated with SO₄²⁻/Na⁺ mass ratio (or nss-SO₄²⁻ concentrations) in summer, suggesting the enhanced atmospheric SO₄²⁻ production over sea ice due to higher dimethyl sulfide (DMS) emissions and/or enhanced oxidation chemistry of DMS. But this relationship becomes negative during winter, suggesting the predominant influence of sea salt aerosols (SSA) from the sea ice surface on atmospheric SO₄²⁻ levels. In winter, the SO₄²⁻/Na⁺ mass ratio appears to be relatively invariable when the P-Time exceeds ∼40–60 %, ranging from ∼0.08 to 0.18. The lower limit of the mass ratio, ∼0.08, likely representing the influence of sea ice SSA on the mass ratio. Based on this value, it is estimated that approximately half of the atmospheric SO₄²⁻ in winter originates from sea ice SSA. These findings highlight the importance of sea ice on aerosol budgets and atmospheric chemistry in polar regions.