Possible methane-induced polar warming in the early Eocene
Possible methane-induced polar warming in the early Eocene
复制标题
始新世早期可能由甲烷引起的极地变暖
作者：
L. Sloan;James C. G. Walker;T. Moore;D. Rea;J. Zachos
对始新世早期气候的考察描绘了这样一个世界：极地环境支持哺乳动物和爬行动物、落叶林、温暖的海洋和罕见的霜冻条件1-5。与此同时，热带海洋表面温度被解释为与目前值相同或略低6。如何使地球极地地区变暖而不使热带地区明显变暖的问题仍然没有解决;预计温室气体的增加将使所有纬度地区变暖。海洋热传输被假定为加热高纬度的机制8 -10，但很难解释实现这一点的动力学7，11。在这里，我们考虑了对始新世湿地面积的估计，并认为甲烷（一种重要的温室气体）的通量在始新世期间可能比现在大得多。甲烷浓度升高会加剧始新世早期的全球变暖，也可能特别防止极地地区冬季的严寒，因为大气甲烷有可能促进光学厚的极地平流层冰云的形成12 -14。
RECONSTRUCTIONSof early Eocene climate depict a world in which the polar environments support mammals and reptiles, deciduous forests, warm oceans and rare frost conditions 1–5. At the same time, tropical sea surface temperatures are interpreted to have been the same as or slightly cooler than present values6. The question of how to warm polar regions of Earth without noticeably warming the tropics remains unresolved; increased amounts of greenhouse gases would be expected to warm all latitudes equally7. Oceanic heat transport has been postulated as a mechanism for heating high latitudes8–10, but it is difficult to explain the dynamics that would achieve this7,11. Here we consider estimates of Eocene wetland areas and suggest that the flux of methane, an important greenhouse gas, may have been substantially greater during the Eocene than at present. Elevated methane concentrations would have enhanced early Eocene global warming, and also might specifically have prevented severe winter cooling of polar regions because of the potential of atmospheric methane to promote the formation of optically thick, polar stratospheric ice clouds12–14.