温帯氷の線形粘性流
Collin M Schohn1, Neal R Iverson1, Lucas K Zoet2
1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA, USA.
まとめ
温帯氷河は,以前考えられていたように非線形ではなく,線形粘性物質として振る舞う. シェア変形実験に基づいたこの発見は 海面上昇予測に影響を与えます
科学分野:
- 氷河学
- 氷の物理
- 気候科学
背景:
- 温帯氷河の変形を正確にモデル化することは 海面上昇を予測するのに不可欠です
- 現在のモデルは,非線形氷の粘度 (n=3-4) を仮定して,しばしばグレンの流動法則に依存しています.
- 温かい氷は粒の境界に液体の水を含み,その機械的振る舞いに影響します.
研究 の 目的:
- 温帯氷河のレオロギー的な振る舞いを,現実的なストレスと水分含有量条件下で調査する.
- 温帯氷の変形のストレート率指数 (n) を決定する.
- 氷の粘度が氷床のモデル化に及ぼす影響を評価する.
主な方法:
- 温帯の氷河で 大規模な剪定変形実験を行いました
- 氷床と氷河流の縁に 関連する範囲内の液体水分と 施されたストレス.
- 粘度指数 (n) を決定するために,ストレスとストレスの割合の関係を分析した.
主要な成果:
- 温帯氷河は,試験条件において線形粘着性 (n ≈ 1.0) を示した.
- これは,グレンの流動法則で仮定された非線形粘度 (n=3-4) と大きく対照的である.
- 観測された線形性は,粒子の境界で拡散圧力溶解と再凍結に起因する.
結論:
- 温帯氷の線形粘着性は 既存の氷の流れモデルに 異議を唱えます
- この発見は 気候変化に対する氷床の反応の予測を 安定させるのに役立つかもしれません
- 線形粘度を組み込む改訂されたモデルは,海面上昇予測を改善することができる.
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