17:15 〜 19:15
[ACC33-P05] グリーンランド北東部EGRIPにおける過去1000年間の遠方及び近傍起源鉱物ダストの変動
キーワード：グリーンランド、アイスコア、鉱物ダスト
Temporal variations in concentration, size distribution, and elemental composition of mineral dust on the Greenland ice sheet are associated with temporal variations in ground surface conditions on their source regions and/or their transportation processes. To understand the relationship between the variations in mineral dust and climate, we analyzed a shallow ice core drilled at the East Greenland Ice Core Project (EGRIP) site. In this study, we report the analysis results of particle size distribution and elemental concentrations in mineral dust.
The ice core was analyzed using a continuous-flow analysis (CFA) system at NIPR. Elemental concentrations (Na, Mg, Al, Si, S, K, Ca, and Fe) were measured using an ICP-MS (Agilent technologies, 7700). For mineral dust analyses, a portion of meltwater was collected using a fraction collector at a depth interval of 0.12 m. Concentrations and size distributions (0.7–18 μm) of mineral dust in the collected samples were measured by a Coulter counter (Beckman Coulter, Multisizer 4e). Additionally, for tritium measurements, ice core samples at depths of 13–15 m were cut and melted. Tritium measurements of the samples were conducted using a scintillation counter (ParkinElmer, Quantulus 1220).
We dated the ice core by annual layer counting using the seasonal variation in Na, with tritium peaks, volcanic layers, and ice layers as fixed date layers. From the results, the ice core was estimated to cover the past approximately 1000 years. The average size distribution of mineral dust mass concentrations showed a unimodal shape with a mode diameter of around 2 μm, suggesting the mineral dust deposited at EGRIP came mainly from remote source regions. After 1900, the concentration of coarse mineral dust (> 5 μm), a proxy for local source dust, varied on a decadal timescale. The coarse dust concentration remained consistently low after 1994, suggesting a decrease in local dust supply to EGRIP. Back-trajectory analysis suggested that the coarse mineral dust originated mainly from snow-free areas in coastal western Greenland. The coarse dust concentration was significantly correlated with the Greenland blocking index, suggesting a link between the local dust supply and atmospheric pressure over Greenland. Estimated concentrations of remote source dust and non-sea-salt Ca increased in the 1960s and 1990s, thus the mineral dust supply from remote desert regions likely increased during those periods. In the presentation, we will also report analysis results for mineral dust variations over a longer timescale.
The ice core was analyzed using a continuous-flow analysis (CFA) system at NIPR. Elemental concentrations (Na, Mg, Al, Si, S, K, Ca, and Fe) were measured using an ICP-MS (Agilent technologies, 7700). For mineral dust analyses, a portion of meltwater was collected using a fraction collector at a depth interval of 0.12 m. Concentrations and size distributions (0.7–18 μm) of mineral dust in the collected samples were measured by a Coulter counter (Beckman Coulter, Multisizer 4e). Additionally, for tritium measurements, ice core samples at depths of 13–15 m were cut and melted. Tritium measurements of the samples were conducted using a scintillation counter (ParkinElmer, Quantulus 1220).
We dated the ice core by annual layer counting using the seasonal variation in Na, with tritium peaks, volcanic layers, and ice layers as fixed date layers. From the results, the ice core was estimated to cover the past approximately 1000 years. The average size distribution of mineral dust mass concentrations showed a unimodal shape with a mode diameter of around 2 μm, suggesting the mineral dust deposited at EGRIP came mainly from remote source regions. After 1900, the concentration of coarse mineral dust (> 5 μm), a proxy for local source dust, varied on a decadal timescale. The coarse dust concentration remained consistently low after 1994, suggesting a decrease in local dust supply to EGRIP. Back-trajectory analysis suggested that the coarse mineral dust originated mainly from snow-free areas in coastal western Greenland. The coarse dust concentration was significantly correlated with the Greenland blocking index, suggesting a link between the local dust supply and atmospheric pressure over Greenland. Estimated concentrations of remote source dust and non-sea-salt Ca increased in the 1960s and 1990s, thus the mineral dust supply from remote desert regions likely increased during those periods. In the presentation, we will also report analysis results for mineral dust variations over a longer timescale.