Kamchatka (southeastern Siberia) ice core records of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls since 1690s: A signal for the tropospheric oxidizing capacity.

There has been much interest about how to identify an ice core signal for oxidizing capacity of the troposphere. This study broadly explains the air-snow transfer/deposition process using ice core records of dicarboxylic (DCAs), ω-oxocarboxylic as well as pyruvic acids and α-dicarbonyls, which are potentially formed by atmospheric oxidation of aromatic hydrocarbons from the continent, incloud-oxidation of isoprene and unsaturated fatty acids from the western North Pacific. An ice core (~152 m long, 304 years) was collected at an ice cap on the Gorshkov crater at the summit of Ushkovsky (56° 04'N, 160° 28'E, altitude: 3903 m) in the Kamchatka Peninsula from southeastern Siberia. Molecular distributions of DCAs showed a predominance of oxalic (C) or succinic (C) acid, followed by malonic (C) acid. ω-Oxoacids are characterized by the predominance of glyoxylic acid (ωC) followed by 8-oxooctanoic (ωC) or 9-oxononanoic (ωC) and then 4-oxobutanoic acid (ωC). These molecular distributions (C ≅ C > C and ωC > ωC = ωC > ωC) in this ice core are different than those from Greenland Site-J and Alaskan Aurora Peak ice cores. The concentration profiles of these DCAs showed significant correlation (R = 0.78, p < 0.01) with the Dalton solar minimum (~1790s-1830s). Diagnostic ratios of these DCAs have clear signal of the Pacific and North Atlantic decadal oscillation with increases in the recent periods, suggesting that the ice core profiles of organic compounds are involved with past biogenic emission from marine biota and incloud-isoprene oxidation. This study reveals the multidecadal variability of the lower tropospheric oxidizing capacity in the North Pacific rim. SYNOPSIS: Polar organic compounds preserved in snow and ice are concomitant with recent climate changes in the western North Pacific rim. SIGNIFICANCE STATEMENTS.