東太平洋の冷却と大西洋の転覆循環は,最後の脱氷期に起きました
Markus Kienast1, Stephanie S Kienast, Stephen E Calvert
1Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, B3H 4J1 Canada. markus.kienast@dal.ca
Nature
|October 20, 2006
まとめ
氷河期における地球気候の変化は,海洋循環の変化に起因する可能性がある. 北大西洋の寒冷期間の太平洋の冷却は,地域的な影響だけでなく,グローバルなリンクを示唆しています.
科学分野:
- パレオセアノグラフィー
- 気候科学 気候科学
- 海洋学 海洋学とは
背景:
- 氷河期における千年規模の気候変動は議論されている.
- これらの変化における熱帯太平洋の海面温度の役割は不明である.
- 以前の研究では,北大西洋の寒冷期が世界の気候と関連していたが,太平洋は関連していなかった.
研究 の 目的:
- 北大西洋の寒冷期と熱帯太平洋の海面温度との関連を調査する.
- 海洋循環の変化が,地球規模の気候変化を引き起こしたかどうかを判断するために.
主な方法:
- アルケノン不飽和を用いた高解像度海面温度再構築.
- 海洋の生産性と上流を推論するために,炭素埋葬フローの分析.
- タイムシンクロニシティを確立するために,古海洋学的記録の年代測定.
主要な成果:
- ハインリッヒ現象1の海面温度下落 ~1°Cは,東熱帯太平洋でハインリッヒ現象1の間に発生した.
- 若いドライアスのイベント中に ~0.5°Cの海面温度低下.
- 表面海洋の生産性の増加は,両寒冷期間の上流が強化されたことを示している.
結論:
- 赤道太平洋の冷却は北大西洋の寒冷期と並行して発生した.
- これらの発見は,千年規模の気候変動が海洋熱ハリン循環の再編によって引き起こされたことを示唆しています.
- 熱帯の海洋と大気間の相互作用は,これらの気候変動を拡大したのかもしれない.
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.
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...
02:44Heating and Cooling Curves
When a substance—isolated from its environment—is subjected to heat changes, corresponding changes in temperature and phase of the substance is observed; this is graphically represented by heating and cooling curves.
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance, q, and its...
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance, q, and its...
03:12Freezing Point Depression and Boiling Point Elevation
Boiling Point Elevation
The boiling point of a liquid is the temperature at which its vapor pressure is equal to ambient atmospheric pressure. Since the vapor pressure of a solution is lowered due to the presence of nonvolatile solutes, it stands to reason that the solution’s boiling point will subsequently be increased. Vapor pressure increases with temperature, and so a solution will require a higher temperature than will pure solvent to achieve any given vapor pressure, including one...
The boiling point of a liquid is the temperature at which its vapor pressure is equal to ambient atmospheric pressure. Since the vapor pressure of a solution is lowered due to the presence of nonvolatile solutes, it stands to reason that the solution’s boiling point will subsequently be increased. Vapor pressure increases with temperature, and so a solution will require a higher temperature than will pure solvent to achieve any given vapor pressure, including one...
01:21Entropy Changes Accompanying Specific Processes
Entropy, a measure of disorder in a system, changes during phase transitions like freezing or boiling. At the transition temperature Ttrs, where two phases are in equilibrium, the phase transition is a reversible process. The entropy change can be calculated from a substance's enthalpy of transition using the equation ΔStrs = ΔtrsH /Ttrs.When a perfect gas expands isothermally from one volume to another, entropy increases logarithmically with volume. Conversely, isothermal compression results...
01:24Freezing Point Depression and Boiling Point Elevation
When a non-volatile solute is added to a pure solvent, it results in the lowering of the freezing point of the solvent. This phenomenon is called freezing point depression. The extent to which the freezing point is lowered depends on the molality of the solute -the number of moles of solute per kilogram of solvent and the cryoscopic constant of the solvent.From the plot of chemical potential, μ, against temperature, it is evident that the μ of both solid and liquid solvents decrease with...