東南極の氷河核におけるより温暖な氷期間の証拠
L C Sime1, E W Wolff, K I C Oliver
1British Antarctic Survey, Cambridge CB3 0ET, UK. lsim@bas.ac.uk
Nature
|November 20, 2009
まとめ
南極の氷のコア記録は,過去の氷河期間の気温は,以前に推定されたよりも大幅に暖かかったことを明らかにしています. 同位体シグネチャーと温度との関係は非線形であり,以前の推定値があまりにも低い可能性があることを示唆しています.
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
- 氷河学 氷河学とは
- 気候モデリング
背景:
- 南極の氷芯は,80万年以上にわたる過去の気候変動に関する重要なデータを提供します.
- 安定した同位体比 (酸素と水素) は,南極の温度を再構築するために使用されます.
- 以前の研究では,同位体比と温度との間に均一で一定な関係があると仮定していた.
研究 の 目的:
- 東南極の氷核における同位体シグネチャーと温度との関係を再評価する.
- 異なる場所と気候期間におけるこの関係の非均一性を調査する.
- 過去の温度再構築,特に氷河期間の再構築を精査する.
主な方法:
- 東南極の3つの氷芯記録の340キロの分析.
- 一般循環モデル (GCM) シミュレーションの統合.
- モデル化された気候アウトプットと同位体データの比較.
主要な成果:
- 温度と同位体シグネチャーの関係は,より温暖な氷期間の東南極の氷芯の場所によって著しく異なります.
- 東南極の氷の同位体の組成は,より温暖な気候における温度変化に対する感度が低下していることを示している.
- これは,特定の場所での正確な温度再構築のために非線形変換が必要であることを示しています.
結論:
- 過去の氷河期間の気温推定値は過小評価されている可能性が高い.
- 南極のピークの氷期間の気温は,現在の気温よりも少なくとも6K高かったかもしれません.
- この発見により,過去の南極の気候を氷芯データを使って再構築するための方法論を改訂する必要が生じました.
関連する概念動画
01:50Global Climate Change
Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global temperatures is well outside of the Earth’s cyclic norms, and evidence for human-caused global climate change is compelling. Paleoclimatology, the study of ancient climate conditions, provides ample evidence for human-caused global climate change by comparing recent conditions with those in the past.
01:21Isothermal Processes
A thermodynamic process that occurs at constant temperature is called an isothermal process. Heat slowly flows into the system or out of the system to maintain thermal equilibrium. Processes involving phase changes like water evaporation into steam or freezing water into ice at a constant temperature are examples of Isothermal Processes.
An ideal gas can also undergo isothermal expansion or compression.
For example, consider 1 mole of an ideal gas inside an isolated cylinder at initial volume V...
An ideal gas can also undergo isothermal expansion or compression.
For example, consider 1 mole of an ideal gas inside an isolated cylinder at initial volume V...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:11Effects of Temperature on Free Energy
The spontaneity of a process depends upon the temperature of the system. Phase transitions, for example, will proceed spontaneously in one direction or the other depending upon the temperature of the substance in question. Likewise, some chemical reactions can also exhibit temperature-dependent spontaneities. To illustrate this concept, the equation relating free energy change to the enthalpy and entropy changes for the process is considered:
02:56The Fossil Record
The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...
02:55The Evidence for Evolution
Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.The collection of fossils within sedimentary rocks give a record of common ancestry and often depicts the history of evolution.