11:00 〜 11:15
[ACC33-08] 電子顕微鏡を用いたグリーンランド北東部アイスコアの過去100年の鉱物起源変動復元
キーワード：アイスコア中の鉱物起源、グリーンランド、SEM-CL分析
The history of mineral dust deposition on the Greenland Ice Sheet provides substantial insight into past global climate and environmental changes. Ice-core dust sources probably vary geographically across the Greenland Ice Sheet because environmental conditions, such as altitude and distance from the coast, differ significantly among regions. However, understanding the spatial and temporal variations in the sources of mineral dust in Greenland ice cores during interglacial periods is challenging due to low dust concentrations.
Here, we present first continuous records of potential sources of mineral dust contained in an ice core obtained from the northeastern Greenland Ice Sheet, covering period from 1910 to 2013. Using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), we identity significant differences between the EGRIP ice core and a northwestern Greenland ice core (SIGMA-D). The EGRIP ice-core shows low temporal variation in dust size and composition, indicating relatively stable sources over the past 100 years. Conversely, the SIGMA-D ice core demonstrates multidecadal variations, reflecting increased dust from the Greenland coastal region during warmer periods (Nagatsuka et al., 2021). The low compositional variability in the EGRIP ice core suggests a smaller contribution from local dust sources. Differences in silicate mineral composition between the two ice cores indicate distinct geological origins.
To identify potential dust source areas, we conducted SEM - cathodoluminescence (CL) analysis of single quartz particles for the EGRIP ice-core dust. SEM-CL detects native imperfections and impurities in quartz that vary with conditions during its formation and subsequent geological background (e.g., metamorphic pressure and temperature, Zinkernagel, 1978), enabling the characterization of dust sources even when dust concentrations are low (Nagashima et al., 2023). Our SEM-CL results indicate that the primary sources of the EGRIP ice-core dust are likely the Asian (Gobi) and African deserts (Sahara). North America cannot be completely ruled out as a potential source, but its contribution is probably minor.
Based on our findings, we identified a shift in the primary sources of dust in the EGRIP core after the 1970s–1980s, with a decrease in contributions from Asia and an increase from Africa over the past 50 years. This shift is likely linked to variations in atmospheric oscillations (NAO and AMO) and/or the recent decrease in Asian dust contributions.
Here, we present first continuous records of potential sources of mineral dust contained in an ice core obtained from the northeastern Greenland Ice Sheet, covering period from 1910 to 2013. Using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), we identity significant differences between the EGRIP ice core and a northwestern Greenland ice core (SIGMA-D). The EGRIP ice-core shows low temporal variation in dust size and composition, indicating relatively stable sources over the past 100 years. Conversely, the SIGMA-D ice core demonstrates multidecadal variations, reflecting increased dust from the Greenland coastal region during warmer periods (Nagatsuka et al., 2021). The low compositional variability in the EGRIP ice core suggests a smaller contribution from local dust sources. Differences in silicate mineral composition between the two ice cores indicate distinct geological origins.
To identify potential dust source areas, we conducted SEM - cathodoluminescence (CL) analysis of single quartz particles for the EGRIP ice-core dust. SEM-CL detects native imperfections and impurities in quartz that vary with conditions during its formation and subsequent geological background (e.g., metamorphic pressure and temperature, Zinkernagel, 1978), enabling the characterization of dust sources even when dust concentrations are low (Nagashima et al., 2023). Our SEM-CL results indicate that the primary sources of the EGRIP ice-core dust are likely the Asian (Gobi) and African deserts (Sahara). North America cannot be completely ruled out as a potential source, but its contribution is probably minor.
Based on our findings, we identified a shift in the primary sources of dust in the EGRIP core after the 1970s–1980s, with a decrease in contributions from Asia and an increase from Africa over the past 50 years. This shift is likely linked to variations in atmospheric oscillations (NAO and AMO) and/or the recent decrease in Asian dust contributions.