Isotopic composition (δ¹⁸О, δ²Н) of glacial ice in Kamchatka: relation with modern climate changes in the Pacific Region

Abstract

The isotopic composition (δ18О, δ2Н) of ice sampled during core drilling of a glacier in the crater of the Ushkovsky volcano in the summer of 2022 (new core) was studied. The ice core 14 m long dates from 2006 to 2022 and covers 16 years of accumulation. The values of δ18О and δ2Н of the ice vary from −16 to −24‰ and from −110.5 to −177.7‰ at average values of −20.5 and −150.2‰, respectively. The deuterium excess varies in depth from 8.7 to 21.3‰ at an average value of 13.7‰. In the isotope diagram, the values of δ18О and δ2Н form a linear trend described by the equation δ2Н = 7.47 × δ18О + 2.9 (R² = 0.98), the slope of the line, different from the global meteoric water line, reflects the mixing of summer and winter precipitation. Ice formed by summer precipitation has high values of δ18О (δ2Н) against a background of low d-excess, while ice of the winter season, on the contrary, has low values of δ18О (δ2Н) and high d-excess. Changes in the values of δ18O and δ2H of ice in depth proceed in antiphase with changes in d-excess, which reflects the dominant role of seasonal accumulation in the formation of the isotope record. The differences in the average values of δ18O and δ2H of the ice from the new core and similar values of ice from the core previously taken in the same crater of the Ushkovsky volcano are due to a change in the structure of the glacier’s alimentation – an increase in the amount of precipitation in the summer-spring season and a decrease in precipitation in the winter period. In addition to changes in the proportion of accumulation of the seasonal precipitation, the isotopic composition of ice is influenced by changes in the source of water vapor, from where air masses bring precipitation to Kamchatka. The use of the d-excess value allowed us to establish that the isotopic parameters of the ice of 2011−2012 and 2021−2022 annual layers were influenced by a pronounced positive anomaly in ocean surface temperatures, which is confirmed by HadSST observations. Thus, the isotopic parameters of glacial ice may serve as an indicator of climate change in the Pacific region.