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当前位置: Science » 生态&环境 » Science:大气中持续升高的二氧化碳实际在给南极洲部分降温


摘要 : 由于大气中的二氧化碳(CO2)浓度持续升高,世界上大多数的地区正在升温,而南极中心近年来却已略有降温。


由于大气中的二氧化碳(CO2)浓度持续升高,世界上大多数的地区正在升温,而南极中心近年来却已略有降温。包括二氧化碳在内的温室气体通常会将那些从地球表面反射回太空的热量锁住,但一年中的大部分时间里,南极东部冰盖(图中右侧那一大片粉色)的大片细狭区域平均而言比大气上层更冷——地球上只有这一处地方是如此。研究人员在即将出版的《地球物理研究快报》的印刷版和网络版上报告说,当研究团队查看一年间所有红外线波长的冰盖表面向上的辐射和大气上层同时向上及向下的辐射之间的总体平衡时,他们发现事实与料想的不同,在南极洲中部,如果空气中含有温室气体,则表面和低层大气实际会向太空中释放更多的能量 。而研究团队的气候模拟提出,短期内向大气中释放更多的二氧化碳会引起该地区表面及低层大气更多的能量损耗。相反的温度趋势部分是由于该地区的高海拔现状;大部分覆盖东部南极的冰盖的表面处于海拔3000米以上的地区,所以比起低海拔地区它可能的温度来说更为寒冷。此外,该区域经常遭遇气象学称之为逆温的现象,即底层大气的温度比上层更冷。对于这片冰冷的大陆的低海拔边缘及世界上的其它地区(甚至西伯利亚和格陵兰)来说,温室效应仍然如预期般在起作用。


Rising atmospheric carbon dioxide actually cools part of Antarctica


In a world wher most regions are warming because of increasing concentrations of atmospheric carbon dioxide (CO2), central Antarctica has been cooling slightly in recent years. Greenhouse gases such as CO2typically trap heat radiated back toward space from the planet’s surface, but large swaths of the East Antarctic Ice Sheet (the broad pink mass on the right side of the image) are, on average, actually colder than the upper layers of the atmosphere for much of the year—the only place on Earth wher that’s true. When the team looked at the overall balance between the radiation upward from the surface of the ice sheet and the radiation both upward and downward from the upper levels of the atmosphere across all infrared wavelengths over the course of a year, they found that in central Antarctica the surface and lower atmosphere, against expectation, actually lose more energy to space if the air contains greenhouse gases, the researchers report online and in a forthcoming Geophysical Research Letters. And adding more CO2 to the atmosphere in the short-term triggered even more energy loss from the surface and lower atmosphere there, the team’s climate simulations suggest. The topsy-turvy temperature trend stems, in part, from the region’s high elevation; much of the surface of the ice sheet smothering East Antarctica lies above an elevation of 3000 meters, so it is much colder than it would be at lower altitudes. Moreover, that region often experiences what meteorologists call a temperature inversion, wher temperatures in the lowest levels of the atmosphere are cooler than those higher up. For the lower-altitude fringes of the icy continent, and for the rest of the world (even Siberia and Greenland), the greenhouse effect still works as expected.

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