グリーンランドの氷の核に記録された北大西洋の振動の動態
1C. Appenzeller and T. F. Stocker, Climate and Environmental Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. M. Anklin, Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721, USA.
まとめ
グリーンランドの氷芯は,北大西洋振動 (NAO) が断続的な気候パターンであり,持続的なものではないことを明らかにします. その活性相は短期的な変動を示し,19世紀半ばから長期的傾向が観察されている.
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
- 気候科学 気候科学
- 大気科学 大気科学
背景:
- 北大西洋振動 (North Atlantic Oscillation,NAO) は,北大西洋地域の天候に影響を与える重要な気候パターンです.
- NAOの長期的な行動と頻度を理解することは,気候モデリングと予測に不可欠です.
- 以前の研究はNAOの変動性を調査しましたが,特定のプロキシデータを用いて何世紀にもわたる詳細な再構築は価値があります.
研究 の 目的:
- 北大西洋振動 (NAO) インデックスの年間プロキシを再構築するために,過去350年間をカバーします.
- NAOの断続的な性質を調査し,そのアクティブ・フェーズとパッシブ・フェーズを特定する.
- NAO変動の支配的な周波数と時間スケールを決定する.
主な方法:
- 気候再構築のプロキシとして,グリーンランドの慎重に選択された氷芯データを活用する.
- 分析された氷芯データに基づいて,NAOの年次指数を作成する.
- 振動周波数と相行動を特定するためにタイムシリーズ分析を適用する.
主要な成果:
- 再構築されたNAO指数は,NAOが一時的にアクティブ・フェーズとパッシブ・フェーズで特徴づけられる断続的な気候振動であることを示しています.
- 単一の,持続的な,多年にわたるNAOの頻度に関する証拠は見つかりませんでした.
- アクティブフェーズでは,NAOのエネルギーは,約15年未満の期間に集中しています.
- 80年から90年の時間スケールの変動は,19世紀半ばから観察されています.
結論:
- NAOは一貫した長期の振動ではなく,断続的な行動を示す.
- 短期変動 (15年未満) は,NAOの活発な段階において優位である.
- より長期的な変動性 (80〜90年) は,より最近,特に19世紀半ば以降に現れ,NAOの動態の潜在的なシフトを示唆しています.
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