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[MIS10-13] Ice sheet/shelf variabilities for the last 2 centuries based on the Be isotope compositions of marine sediments from off Totten Glacier, East Antarctica
Keywords:Be isotopes, Circumpolar Deep Water, Totten Glacier, Surface marine sediment
Accelerated mass loss of the Antarctic Ice Sheet has been linked to the inflow of Circumpolar Deep Water (CDW). However, the role of the CDW and its temporal changes have been poorly known. Beryllium isotope compositions of Antarctic sediments have been proposed as useful proxies for the recent ice shelf/sheet variabilities (e.g., White et al., 2019; Iizuka et al., 2023). To reconstruct the CDW inflow and Antarctic ice sheet changes over the last millennium, we analyzed the Be isotope compositions of the series of marine sediments recovered during the 61st Japanese Antarctic Research Expedition (2019-2020) from off Totten Glacier. We utilized the uppermost layers of the sediments from 11 sites and 22cm sections from the 2 sites (St.14B and 26) to investigate 2D distribution and temporal changes. The St.26 is located off Totten Glacier, and St.14B is neat the curving front. These samples were used for grain size analysis and 210Pb dating before the Be isotope analysis.
We observed the distinct 10Be concentrations at the CDW inflow sites and highly concentrated 9Be concentrations off the glacier and its marginal sites. These findings indicate utilities of 10Be as proxies for CDW inflow and 9Be for debris supplied from underneath the glacier. Based on 210Pb dating, sedimentary records at St.14B and St.26 span from 1880 and 1810 AD, respectively. The grain size variations of sediments at both sites are mostly uniform with depth, suggesting relatively stable depositional environments. Despite invariable 10Be concentrations throughout the two sections, a gradual increase of 9Be concentrations at St.14B suggests an increase in debris supply since the 1950s. These data indicate that CDW inflow has been stable over the past 140-210 years, but the ice sheet/shelf retreat may have accelerated since the 1950s. To better elucidate the relationship between past CDW and ice sheet changes, further investigations are required based on the other proxies with longer timescales.
References
White, D.A., Fink, D., Post, A.L., Simon, K., Golton-Fenzi, B., Foster, S., Fujioka, T., Jeromson, M.R., Blaxell, M. (2019) Beryllium isotope signatures ice shelves and sub-ice shelf circulation, Earth and Planetary Science Letters, 505, 86-95.
Iizuka, M., Seki, O., Wilson, D., Suganuma, Y., Horikawa, K., van de Flierdt, T., Ikehara, M., Itaki, T., Irino, T., Yamamoto, M., Hirabayashi, M., Matsuzaki, H., and Sugisaki, S. (2023) Multiple episodes of ice loss from the Wilkes Subglacial Basin during the Last Interglacial, Nature communications, 14(1).
We observed the distinct 10Be concentrations at the CDW inflow sites and highly concentrated 9Be concentrations off the glacier and its marginal sites. These findings indicate utilities of 10Be as proxies for CDW inflow and 9Be for debris supplied from underneath the glacier. Based on 210Pb dating, sedimentary records at St.14B and St.26 span from 1880 and 1810 AD, respectively. The grain size variations of sediments at both sites are mostly uniform with depth, suggesting relatively stable depositional environments. Despite invariable 10Be concentrations throughout the two sections, a gradual increase of 9Be concentrations at St.14B suggests an increase in debris supply since the 1950s. These data indicate that CDW inflow has been stable over the past 140-210 years, but the ice sheet/shelf retreat may have accelerated since the 1950s. To better elucidate the relationship between past CDW and ice sheet changes, further investigations are required based on the other proxies with longer timescales.
References
White, D.A., Fink, D., Post, A.L., Simon, K., Golton-Fenzi, B., Foster, S., Fujioka, T., Jeromson, M.R., Blaxell, M. (2019) Beryllium isotope signatures ice shelves and sub-ice shelf circulation, Earth and Planetary Science Letters, 505, 86-95.
Iizuka, M., Seki, O., Wilson, D., Suganuma, Y., Horikawa, K., van de Flierdt, T., Ikehara, M., Itaki, T., Irino, T., Yamamoto, M., Hirabayashi, M., Matsuzaki, H., and Sugisaki, S. (2023) Multiple episodes of ice loss from the Wilkes Subglacial Basin during the Last Interglacial, Nature communications, 14(1).