Antarctic Ice Core Records of Saturated (C8–C30), Unsaturated (C16:1, Cis/Trans C18:1, and C18:2), and Branched-Chain (iC10–iC16) Fatty Acids and Dehydroabietic Acid from Preindustrial to Near-Present Time: Implications for Global Warming and Climate Changes

Abstract

There is significant interest in identifying the impacts of climate changes on the Queen Maud Land-Mizuho Plateau of East Antarctica (69.05°S; 40.47°E, altitude: 1057 m mean above sea level). The atmospheric particles in polar regions can be deposited on snow and ultimately preserved on the ice sheet. Here, we explain the source and air-to-snow deposition process using the East Antarctica H-15 ice core records of lower molecular weight unsaturated (u-LFAs), saturated (s-LFAs; C₈–C₁₉), and higher molecular weight saturated (HFAs; C₂₀–C₃₀), and branched-chain (b-LFAs) fatty acids (FAs) (35 species) as regional paleoclimate signals. Molecular distributions of FAs in several ice layers are characterized by the predominance of α-linoleic (C_18:2) or oleic (C_18:1) acid, being different from the distribution of ice cores and snow pit samples from the Northern Hemisphere. We found historical increases in the concentrations of u-LFAs, s-LFAs, and b-LFAs in the ice core after 1850s, which are mainly derived by an enhanced sea-to-air emission from sea-surface microlayers due to the higher marine productivity during warmer periods. In contrast, HFAs of terrestrial higher plant origin also showed the recent concentration increases. However, the correlations of u-LFAs, s-LFAs, and HFAs with dehydroabietic acid (a tracer of wildfire burning of higher plant resins) are rather weak (R² = 0.03, 0.02, and 0.19, respectively) in the ice core, suggesting different sources of FAs enhanced by meridional transport from the lower latitudes after the 1850s. The concentrations of these compounds are well correlated (p < 0.05) with the known climatic events, e.g., land and ocean temperature anomalies, sea ice extend (SIE), decreasing trend of stratospheric ozone, total solar irradiance, and Antarctic oscillation. Our findings suggest a regime shift in FA concentrations between the 1850s to 1990s, which could be associated with sea ice retreat in response to recent global warming that promotes more sea-to-air emission of u-LFAs.