オリゴセーン/ミオセンの境界にある東南極氷床の軌道による振動
T R Naish1, K J Woolfe, P J Barrett
1Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt, New Zealand. t.naish@gns.cri.nz
Nature
|October 19, 2001
まとめ
南極の氷床は,オリゴセーン/ミオセンの移行期に軌道サイクルによって変動した. 堆積物核は,東南極の氷床の間の直接的なつながりを明らかにしています.
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
- パレオセアノグラフィー
- 気候科学 気候科学
背景:
- 南極の氷床は,より高いCO2レベルを持つより温暖な気候の間に,34~1500万年前 (ミール) に不安定であった可能性があります.
- 酸素同位体記録は,軌道周期が地球温暖化と氷の量に影響を与えたことを示唆しているが,南極の氷床の振動の直接的な証拠は欠けていた.
研究 の 目的:
- 南極の氷の量における推論された変化を,氷床の振動の直接的な証拠で校正するために.
- 東南極の氷床の範囲をオリゴセーン/ミオセーン移行期の軌道サイクルと直接結びつけるため.
主な方法:
- ロス海西部の浅い海の中核からの堆積物データの分析.
- 年代測定モデルを用いた氷石の配列と侵食的な隙間の年代測定.
- 氷の体積の変化と軌道周期 (斜率と偏心) の相関.
主要な成果:
- 堆積物の中核の年代がよく知られている周期的な変動は,東南極の氷床の範囲を軌道周期 (24.1-23.7 Myr ago) と直接結びつける.
- <450 kyrに制限された,急速に堆積したグラシマリンの配列は,傾斜 (40 kyr) と偏心 (125 kyr) 周波数が制御された氷の縁の振動を示します.
- 侵食的な休憩 (250 kyr) は,約23.7 Myr前の大規模な地球的な冷却と氷床の膨張イベント (Mi1) の直接的な証拠を提供します.
結論:
- 軌道周期は,オリゴセーン/ミオセンの移行期における南極の氷床の動態に大きな影響を与えた.
- この研究は,軌道強制が東南極の氷床の行動に与える影響の直接的な証拠を提供します.
- この発見は,2370万年前の大規模な冷却と氷の膨張イベント (Mi1) に関する以前の推論を裏付けている.
関連する概念動画
Phase 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...
Magnetostatic Boundary Conditions
An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...
Frictional Forces on Flat Belts
Flat belts are commonly used in various industrial applications for transmitting power from one pulley to another. When a flat belt is wrapped around a set of pulleys, it experiences different tensions at the driving pulley ends due to the friction between the belt and pulley surface. When the pulley moves in a counterclockwise direction, the tension T2 on the opposite side of the pulley where the belt is moving away from is higher than the tension T1 on the side where the belt is moving...
Rolling Resistance
When a solid cylinder rolls steadily on a rigid surface, the normal force applied by the surface on the cylinder is perpendicular to the tangent at the contact point. However, since no materials are entirely rigid, the surface's reaction to the cylinder involves a range of normal pressures.
For instance, imagine a hard cylinder rolling on a comparatively soft surface. The cylinder's weight compresses the surface beneath it. As the cylinder moves, the material in front of it slows down due to...
For instance, imagine a hard cylinder rolling on a comparatively soft surface. The cylinder's weight compresses the surface beneath it. As the cylinder moves, the material in front of it slows down due to...
Masonry in Cold and Hot Weather Conditions
In cold weather, masonry construction requires specific precautions to ensure mortar does not freeze before curing, as this can significantly weaken its strength and watertightness. Mortar temperature should be maintained between 60°F and 80°F to support proper hydration and curing. Below 40°F, mortar water must be heated, but should not exceed 120°F as high temperatures can reduce mortar's compressive and bond strength.
Other key practices include keeping masonry units and sand dry and...
Other key practices include keeping masonry units and sand dry and...
Frost Action on Concrete
Concrete structures in cold climates, such as those along roadsides, can retain moisture. This moisture makes them susceptible to frost-related damage when temperatures fall below freezing. Adding moisture worsens the damage during temperature fluctuations, leading to repeated freezing and thawing. De-icing salts, spread over these structures to melt ice, add to the freeze-thaw cycle, and draw even more moisture into the concrete.
This freeze-thaw cycle primarily causes surface scaling, where...
This freeze-thaw cycle primarily causes surface scaling, where...


