最後の氷河期の間,大気中の14C濃度の非常に大きな変動があった
J W Beck1, D A Richards, R L Edwards
1NSF-Arizona Accelerator Mass Spectrometry Facility, Department of Physics, University of Arizona, Tucson, AZ 85721, USA. wbeck@physics.arizona.edu
まとめ
大気中の炭素14 (14C) レベルは4万5千年前から1万1千年前にかけて大きく変動し,太陽や磁気の影響を超えた主要な炭素サイクルシフトを示しています.
科学分野:
- 古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは
- 地質化学 地質化学
- 放射線年代測定法による年代測定
背景:
- 大気中の放射性炭素 (14C) の変動は,地球の過去の気候と炭素循環の動態についての洞察を提供します.
- スタラグミットは,過去の環境条件を再構築するための貴重なアーカイブとして機能します.
研究 の 目的:
- 大気中の14C濃度の高解像度記録を4万5千年前から1万1千年前まで生成する.
- この期間の主要な14C変動の要因を調査する.
主な方法:
- スタラグミットの高精度熱イオン化質量スペクトロメトリック230Th年代測定.
- スタラグミットの加速器質量スペクトロメトリック14C測定.
- 氷核からの宇宙生成同位体記録 (36Cl,10Be) との比較.
主要な成果:
- 大気中のデルタ14Cの長期的上昇は45〜33kaから観察され,特に44.3〜43.3kaの間,急速な遠足が観察されました.
- デルタ14Cの有意な低下は26から11ka,約700から約100/mlで,わずかな変動があった.
- 観測された14Cパターンは,宇宙的同位体ピークとの相関を示唆しています.
結論:
- 太陽と地磁場の変動だけでは,観測された14C記録を説明することはできません.
- 地球の炭素サイクル内の大幅な変動は,14C記録の主要な特徴を説明するために必要である.
- この発見は,大気中の14Cレベルを形作る際の,外的な強制力と内部的な炭素サイクルダイナミクスの複雑な相互作用を強調しています.
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