Fifty years of firn evolution on Grigoriev ice cap, Tien Shan, Kyrgyzstan

Machguth, H.; Eichler, A.; Schwikowski, M.; Brütsch, S.; Mattea, E.; Kutuzov, S.; HeuleM; Usubaliev, R.; Belekov, S.; Mikhalenko, V.N.; Hoelzle, M.; Kronenberg, M.

Авторы: Machguth H., Eichler A., Schwikowski M., Brütsch S., Mattea E., Kutuzov S., HeuleM, Usubaliev R., Belekov S., Mikhalenko V.N., Hoelzle M., Kronenberg M.
Журнал: The Cryosphere
Номер: 18
Год издания: 2024
Издательство: Copernicus Group
Местоположение издательства: Germany
Первая страница: 1633
Последняя страница: 1646
DOI: 10.5194/tc-18-1633-2024
Аннотация: Grigoriev ice cap, located in the Tien Shan mountains of Kyrgyzstan, has a rich history of firn and ice coredrilling starting as early as 1962. Here we extend the exceptional record and describe an 18 m firn core, drilled in February 2018 on the summit of Grigoriev ice cap, at 4600 m a.s.l.The core has been analyzed for firn stratigraphy, major ions,black carbon, water stable isotope ratios and total β activity.We find that the core covers 46±3 years and overlaps by 2 to3 decades with legacy cores. A good agreement is found inmajor ion concentrations for the overlapping period. Concentrations of black carbon and major ions are reduced since theearly 2000s, indicating the onset of meltwater runoff. Nevertheless, general concentration trends of these species are consistent with observations and Central Asian ice core records,since emissions were highest during periods when melt influence was negligible. The record of water stable isotopes doesnot reflect the strong increase of air temperatures during thelast decades, implying that water stable isotope ratios ceasedto be proxies of temperature variations at this site. Apart fromrunoff evidence, however, the firn’s thermal regime appearsremarkably unchanged. Firn temperatures in 2018 were thehighest on record (∼ −1.6 °C at ∼ 17 m depth). However,temperatures in 2023 are again similar to the early 2000s at∼ −2.5 °C. Furthermore, we find little change in net accumulation since the 1980s. We hypothesize (i) that firn temperatures are stabilized by the removal of latent heat throughlateral meltwater runoff, and (ii) that mass loss by runoff iscompensated by an increase in accumulation. Data from anearby weather station support the latter hypothesis.
Добавил в систему: Михаленко Владимир Николаевич

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Fifty years of firn evolution on Grigoriev ice cap, Tien Shan, Kyrgyzstanстатья

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