太平洋上部における南極反転循環の減速
Michael J McPhaden1, Dongxiao Zhang
1NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington 98115, USA. mcphaden@pmel.noaa.gov
Nature
|February 8, 2002
まとめ
太平洋の気温は,気候と海洋生物に影響を与えます. 観測は,1970年代以降の海洋循環の減速を示しており,冷たい水の上流が減少し,海面温度が上昇しています.
科学分野:
- 海洋学 海洋学とは
- 気候科学 気候科学
- マリン・バイオロジー マリン・バイオロジー
背景:
- 太平洋の気温変動は,北米の気候と海洋生態系に大きな影響を及ぼしています.
- これらの温度変化を誘発する正確な物理的メカニズムは,まだ完全に理解されていません.
- 現在の理論では,熱帯地域と亜熱帯地域間のメリディアン転覆循環 (MOC) が重要な役割を果たしていることを示唆しています.
研究 の 目的:
- 太平洋の南極反転循環の長期的傾向を調査する.
- 循環の変化が赤道上流と海面温度に与える影響を測定する.
- 海洋の二酸化炭素排出に対する循環変化の影響を評価する.
主な方法:
- 過去50年にわたる観測データの分析.
- メリディオンの転覆循環の変化の定量化.
- 赤道上の上流量と海面温度の動向の測定.
主要な成果:
- 太平洋の南極の転覆循環は,1970年代から減速しています.
- 赤道上流は約25%減少した (47 x 10^6 から 35 x 10^6 m^3 s^-1 に).
- この減少は,赤道的な海面温度が0.8°C上昇し,CO2排出量が減少したことと関連しています.
結論:
- 観測されたMOCの減速は,近年の温暖化と赤道太平洋のCO2流の変化の主な要因である.
- 海洋循環の変化は,海洋生態系と地球規模の気候規制に大きな影響を及ぼします.
- 海洋循環,気温,大気中のCO2との間のフィードバックメカニズムを完全に理解するには,さらなる研究が必要です.
関連する概念動画
Gyroscope: Precession
Precession can be demonstrated effectively through a spinning top. If a spinning top is placed on a flat surface near the surface of the Earth at a vertical angle and is not spinning, it will fall over due to the force of gravity producing a torque acting on its center of mass. However, if the top is spinning on its axis, it precesses about the vertical direction, rather than topple over due to this torque. Precessional motion is a combination of a steady circular motion of the axis and the...
Propagation Speed of Electromagnetic Waves
Electromagnetic waves are consistent with Ampere's law. Assuming there is no conduction current Ampere's law is given as:
Joule-Thomson Effect
The Joule-Thomson effect, also known as the Joule-Kelvin effect, describes the temperature change of a fluid when it is forced through a valve or porous plug while keeping it in a thermally insulated environment. This experiment is called a throttling process. This is an important effect widely used in refrigeration and the liquefaction of gases.
This experiment forces high-pressure gas through a throttle valve or a porous plug to a lower-pressure region. The gas expands as it passes through to...
This experiment forces high-pressure gas through a throttle valve or a porous plug to a lower-pressure region. The gas expands as it passes through to...
Speed of a Transverse Wave
The speed of a wave depends on the characteristics of the medium. For example, in the case of a guitar, the strings vibrate to produce the sound. The speed of the waves on the strings and the wavelength determine the frequency of the sound produced. The strings on a guitar have different thicknesses but may be made of similar material. They have different linear densities, and the linear density is defined as the mass per length.
One of the key properties of any wave is the wave speed. Light...
One of the key properties of any wave is the wave speed. Light...
Coriolis Force
An accelerating particle experiences a force equal to the mass multiplied by the acceleration in an inertial frame of reference. Consider a particle in a non-inertial frame of reference, such as a sliding ball on a rotating table. The acceleration of the ball in this rotating reference frame is different than in the intertial frame, which modifies its equation of motion. The fictitious forces acting additionally on a rotating frame of reference alter Newton's Second Law expression. Centripetal...
Irrotational Flow
Irrotational flow is characterized by fluid motion where particles do not rotate around their axes, resulting in zero vorticity. For a flow to be irrotational, the curl of the velocity field must be zero. This imposes specific conditions on velocity gradients. For instance, to maintain zero rotation about the z-axis, the gradient condition:


