Vertical distributions of low molecular weight dicarboxylic acids in the Greenland ice core (scientific paper)

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Forty three ice sections taken from the Greenland ice core (Site-J, 206m long, ca. 450 yrs old) have been studied for low molecular weight dicarboxylic acids using capillary gas chromatography and mass spectrometry. A homologous series of α, ω-dicarboxylic acids (C_2-C_<10>) and phthalic acid were detected in the ice core samples. Their molecular distributions show a predominance of succinic acid (C_4) followed by oxalic acid (C_2), malonic acid (C_3), glutaric acid (C_5), and azelaic acid (C_9). The distribution patterns suggest that the dicarboxylic acids are photochemical oxidation products of biogenic compounds such as marine-derived unsaturated fatty acids rather than anthropogenic organic matter. Among the diacids, azelaic acid (C_9) showed the most drastic changes : its concentrations were low before the 1890s, but abruptly increased after that period to recent years showing a maximum in the 1940s. Because C_9 diacid is a specific photochemical oxidation product of unsaturated fatty acids, its historical trend suggests that sea ice coverage around Greenland was significantly enhanced before the 1890s and retreated in the 20th century. The maximum concentration of C_9 diacid observed in the 1940s is consistent with a reported maximum of sea surface temperature (SST) in the Arctic and a reported decrease of drift ice around Iceland.
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