急速な氷河化と2段階の海面上昇が,最後の氷河期最大期に突入する
Yusuke Yokoyama1,2,3, Tezer M Esat4,5, William G Thompson6
1Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan. yokoyama@aori.u-tokyo.ac.jp.
Nature
|July 27, 2018
まとめ
グレートバリアリーフの海面が20メートル下がり 急速な上昇が続きました 氷河期から暖かい時期への 気候モデルのための重要なデータです
科学分野:
- 古代気候学
- 四半期地質学
- 海洋学
背景:
- 最後の氷河期 (Last Glacial Maximum,LGM) は地球で最も寒い時期であり,大気中のCO2と海面の温度が低いことが特徴でした.
- 世界平均海水位 (GMSL) は約3万1千年前に大幅に低下し,ホロセンの1万年の脱氷に先立ちました.
- LGM-ホロセンの移行を理解することは 気候モデルを改良し 将来の気候変動を予測するために不可欠です
研究 の 目的:
- グレートバリアリーフのLGM-ホロセンの移行期における海面の変化のタイミングと規模を正確に決定する.
- 地域の海面データを用いてGMSLと氷床の動態モデルを制約する.
- 過去と将来の気候変動の気候モデルを改善するための堅実なデータを提供すること.
主な方法:
- グレート・バリア・リーフのシェルフ・エッジから回収された化石のサンゴとサンゴ藻類の分析
- 海面変動の正確な時間軸を確立するために これらの化石集合の放射線年代測定
- 地域の相対海面データからGMSLを導き出すために,氷河同位体モデルを適用する.
主要な成果:
- 約20メートルの相対的な海面下落は21,900年から20,500年前に発生し,現代の海面に比べて -118メートルに達しました.
- この減少の後,相対的な海水位は年間平均3.5mmで約4000年間上昇した.
- GMSLの推定では -125メートルから -130メートルの低さで,LGMは約20500年前に頂点に達しました.
結論:
- グレート・バリア・リーフは海面の大幅な低下と その後の急速な上昇を経験し 直接的に地球上の氷の量増加に繋がりました
- これらの発見は,氷床や地質学的な影響から独立して,海面の変化を高解像度で記録します.
- 導出されたGMSLデータは,LGM-ホロセンの移行についての理解を洗練し,気候モデリングの制約を改善します.
関連する概念動画
Maximum Deflection
1.0K
When analyzing beams under unsymmetrical loads, such as a train moving on a bridge, it is crucial to accurately determine the points of maximum stress and deflection. The process involves identifying the maximum deflection of the beam, which may not always occur at its midpoint due to the uneven distribution of the load.
The maximum deflection occurs at a specific point, known as point O, where the tangent to the deflection curve is horizontal. To find point O, the slope of the tangent at any...
The maximum deflection occurs at a specific point, known as point O, where the tangent to the deflection curve is horizontal. To find point O, the slope of the tangent at any...
1.0K
Maximum Power Transfer
934
Numerous practical applications within engineering disciplines, such as telecommunications, necessitate optimizing power delivery to a connected load. This pursuit, however, entails inherent internal losses, which can either equal or exceed the power supplied to the load. The Thevenin equivalent circuit is helpful in finding the maximum power a linear circuit can deliver to a load. It is assumed in this context that the load resistance can be adjusted.
By substituting the entire circuit with...
By substituting the entire circuit with...
934
Maximum Size of Aggregate
564
The maximum size of aggregate is defined as the aperture of the sieve retaining 15 percent or more of the particles present in the aggregate sample. The aggregate's maximum size impacts the concrete's water requirement, workability, and strength. Larger aggregates reduce the surface area needing cement paste coverage, which can lower water needs, thereby allowing a decrease in the water-to-cement ratio when the desired workability and richness of the mix are to be maintained, which can...
564
The Maximum Power Transfer Theorem
1.2K
Consider a linear AC Thevenin equivalent circuit connected to a load impedance.
The load connected draws the current, and the circuit delivers the power to the load. The alternating current flowing through the load is determined using the rectangular form of voltages, currents, network impedance, and load impedance. The average power delivered to the load is obtained from the product of the square of current and load resistance.
The load connected draws the current, and the circuit delivers the power to the load. The alternating current flowing through the load is determined using the rectangular form of voltages, currents, network impedance, and load impedance. The average power delivered to the load is obtained from the product of the square of current and load resistance.
1.2K
Effect of Sea Water on Concrete
1.1K
Concrete exposed to seawater can undergo degradation like the dissolution of ettringite and gypsum, increasing the material's porosity and decreasing its strength. In contrast, the crystallization of salts within the concrete's pores can cause expansion, particularly above the waterline where evaporation occurs. Nonetheless, this expansion only happens when seawater, enabled by the concrete's permeability, manages to infiltrate the structure.
Concrete in areas between tide marks,...
Concrete in areas between tide marks,...
1.1K
Maximum Power Flow and Line Loadability
621
The maximum power flow for lossy transmission lines is derived using ABCD parameters in phasor form. These parameters create a matrix relationship between the sending-end and receiving-end voltages and currents, allowing the determination of the receiving-end current. This relationship facilitates calculating the complex power delivered to the receiving end, from which real and reactive power components are derived.
621


