Video Experimental Relacionado
Updated: Jul 12, 2026
11:11
Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation
Published on: May 2, 2016
En el Mioceno Medio, el enfriamiento del Océano Sur y la expansión de la criosfera antártica
Amelia E Shevenell1, James P Kennett, David W Lea
1Department of Geological Sciences and Marine Science Institute, University of California, Santa Barbara, CA 93106-9630, USA. ashevenell@umail.ucsb.edu
Science (New York, N.Y.)
|September 18, 2004
Resumen
La transición climática del Mioceno Medio vio un enfriamiento significativo en el suroeste del Pacífico, impulsado por cambios en la circulación oceánica, no por la reducción de CO2. Este enfriamiento precedió a la expansión del hielo antártico, revelando complejas retroalimentaciones climáticas.
Área de la Ciencia:
- La paleoceanografía es la paleoceanografía.
- Ciencias del clima Ciencias del clima Ciencias del clima Ciencias del clima
- Geología marina Geología marina.
Sus antecedentes:
- La transición climática del Mioceno medio (hace 14,2 a 13,8 millones de años) fue un período crítico de enfriamiento global.
- Las hipótesis anteriores sugerían que la reducción de dióxido de carbono atmosférico (CO2) era el principal impulsor de esta transición.
- Comprender la interacción del forzamiento orbital, la circulación oceánica y la expansión de la criosfera es clave para reconstruir la dinámica climática pasada.
Objetivo del estudio:
- Para reconstruir las temperaturas de la superficie del mar en latitudes altas (SSTs) durante la transición climática del Mioceno medio.
- Para investigar los impulsores del enfriamiento del Océano Sur y la expansión de la criosfera antártica.
- Desafiar o apoyar las hipótesis existentes con respecto al papel de la reducción de CO2 en el cambio climático del Cenozoico.
Principales métodos:
- Análisis de las proporciones de magnesio/calcio en foraminíferos planctónicos del Océano Austral para determinar las paleotemperaturas.
- Comparación de SSTs reconstruidos con proxies globales del ciclo del carbono y tendencias del volumen de hielo.
- Evaluación de la influencia del forzamiento orbital (eccentricidad) en la variabilidad climática.
Principales resultados:
- Las SST de latitudes altas del suroeste del Pacífico se enfriaron 67°C durante la transición climática del Mioceno medio.
- El enfriamiento gradual fue acelerado por el forzamiento de la excentricidad y ocurrió aproximadamente 60.000 años antes de la expansión de la criosfera antártica.
- La evidencia sugiere que los cambios en la circulación oceánica, en lugar de la reducción episódica de CO2, iniciaron el enfriamiento y el crecimiento del hielo.
Conclusiones:
- Los cambios en el ritmo orbital de la circulación oceánica alteraron significativamente el transporte meridional de calor y vapor.
- Estos cambios en la circulación desencadenaron el crecimiento del hielo antártico y el posterior enfriamiento global, desafiando la hipótesis de reducción de CO2.
- Los hallazgos resaltan la importancia de las retroalimentaciones océano-atmósfera-hielo en la regulación del clima durante los intervalos de bajo CO2 atmosférico2.
Videos de Conceptos Relacionados
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...
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...
01:22Thermal Expansion
The expansion of alcohol in a thermometer is one of many commonly encountered examples of thermal expansion, which is the change in size or volume of a given system as its temperature changes. The most visible example is the expansion of hot air. When air is heated, it expands and becomes less dense than the surrounding air, which then exerts an upward force on the hot air to, for example, make steam and smoke rise, and hot air balloons float. The same behavior happens in all liquids and gases,...
01:27Thermal expansion and Thermal stress: Problem Solving
San Francisco's Golden Gate Bridge is exposed to temperatures ranging from -15 °C to 40 °C. At its coldest, the main span of the bridge is 1275 m long. Assuming that the bridge is made entirely of steel, what is the change in its length between these temperatures?
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55 °C.
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55 °C.
01:28Magnetostatic 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...
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...