摘要
使用大气-海洋环流模式 CESM1.2.2,在不同的轨道配置情况下,对晚奥陶纪地球气候进行一系列敏感性试验.结果表明,地球轨道变化可以使局地年平均温度变化幅度超过 5.5℃,季节温度变化幅度超过23℃,岁差变化对全球平均温度的影响小于 0.2℃;当地球自转轴倾角从 22.5°变为 24.5°时,由于高纬度接收的年平均太阳辐射通量增加,加上冰雪的反馈,全球平均温度可以增加约 1℃.地球轨道变化对全球平均降水量的影响有限,但对降水的时空分布影响较大.岁差的变化能够控制热带辐合带的南北移动,地球自转轴倾角增大可以使两极地区降水增多,两者共同影响全球的降水分布.地球轨道变化对季风区的分布格局影响很大,岁差的变化使全球季风区面积变化幅度超过 40%,中-高纬度季风区还受到地球自转轴倾角的影响,面积变化幅度可达到约 10%.尽管晚奥陶纪全球地表平均温度超过 18℃,但在大部分轨道配置情况下,南极附近的大陆仍然有深厚的积雪,具备形成广泛冰盖的潜力.
Abstract
A series of sensitivity experiments on the Late Ordovician Earth's climate under different orbital configurations were conducted using the atmosphere-ocean general circulation model CESM1.2.2.It was found that the local annual mean surface temperature could vary by more than 5.5℃and the seasonal temperature by more than 23℃due to changes in orbital parameters.The global mean temperature was affected by less than 0.2℃due to precession,and an increase of about 1℃in the global mean temperature could be caused by a change in obliquity from 22.5° to 24.5°,due to the annual mean solar radiation received at high latitudes,together with the ice-albedo feedback.The global mean precipitation rate was found not to be impacted by orbital changes,but its spatial and temporal distribution was highly impacted;the north-south shift of the intertropical convergence zone was controlled by the precession,and an increase in precipitation at the poles was caused by increases in the obliquity.A great impact on the spatial pattern of summer monsoonal regions was also caused by orbital changes.A change in the global monsoon area by more than 40%could be caused by changes in precession;a mild effect on the mid-latitude and high-latitude monsoon area of approximately 10%was caused by obliquity.Although Late Ordovician was overall warm with its global mean surface temperature exceeding 18℃,deep snow can be accumulated over large areas of continents in the southern hemisphere under most orbital configurations,indicating the possibility of the formation of large ice sheets.
维普
万方数据