摘要
轨道尺度上的水循环及其对轨道三要素、温室气体和冰盖的响应一直是古气候学界研究的热点科学问题之一.海冰和降水作为水循环的两个重要组成部分,其变化更是备受关注.研究海冰和降水在轨道尺度上的变化,特别是对外部驱动的响应机理、内部过程和反馈机制,有望对现代海冰和降水变化的理解及其未来趋势预测提供长尺度的背景参考.最新研究结果表明,在轨道尺度上北半球海冰对太阳辐射的变化更敏感,而南半球海冰对温室气体的变化更敏感.就轨道三要素而言,北半球海冰主要受岁差控制,而南半球海冰主要受斜率控制.岁差、斜率和CO_(2)在全球不同区域降水中的相对重要性随时间和空间不同而发生变化.受赤道最大太阳辐射影响,热带降水中还含有明显的半岁差信号.此外,缓慢的轨道尺度太阳辐射变化可以通过影响北极海冰变化来引起大西洋经向翻转环流(Atlantic meridional overturning circulation, AMOC)百年-千年尺度的突变,从而引起全球温度和降水随之发生改变.在东亚季风区,中国南方夏季降水受冰盖影响显著,冰盖主要通过影响热带辐合带(inter-tropical convergence zone, ITCZ)的季节性摆动来影响降水;而中国北方夏季降水主要受太阳辐射控制,以岁差信号占主导;太阳辐射和冰量对夏季风降水的影响具有较强的区域性和非线性特征.
Understanding the variations of water cycle on orbital timescale and their response to astronomical parameters,greenhouse gases(GHG)and ice sheets is one of the focuses in paleoclimate study.Sea ice and precipitation,two important components of the water cycle,are paid much attention.A better understanding of their variations on orbital timescale,especially their response to external forcing and related processes and feedbacks,could provide insight on their long-term variations in the future.The latest research results show that,on orbital scale,the Arctic sea ice is more sensitive to insolation,while the Southern Ocean sea ice is more sensitive to GHG.Under the combined influence of insolation and GHG,the last nine interglacials all have much less summer Arctic sea ice,as compared to both the present-day and the future,due to the much higher Northern Hemisphere(NH)summer insolation.As compared to the future,the last nine interglacials all have much more annual and seasonal Southern Ocean sea ice due to their much lower CO_(2).In terms of the astronomical parameters,the Arctic sea ice is more influenced by precession,whereas obliquity plays a more important role in the Southern Ocean sea ice.The different responses of Arctic and Southern Ocean sea ice to astronomical parameters and CO_(2) are mainly due to their different geographical locations.The Arctic ocean is relatively closed and it is located in the northern highest latitudes,which make it only receives very little insolation during winter and it is mainly influenced by precession-dominated summer insolation.The summer insolation not only influences the summer Arctic sea ice,but also has an effect on the winter one through the summer remnant effect.In addition,the Arctic sea ice is also affected by the vegetation in the northern mid and high latitudes,which is mainly dominated by precession.As compared to the Arctic,the latitudes of Southern Ocean are lower and it is more open,which make it is more sensitive to the annual insolation and CO_(2).The relative effect of precession,obliquity and CO_(2) on precipitation largely depends on different regions and time periods.The tropical precipitation changes also show obvious half-precession cycles in response to the maximum equatorial insolation.In addition,astronomically-induced slow variation of insolation can trigger abrupt changes of the Atlantic meridional circulation(AMOC)through sea ice-ocean interactions in the Labrador and Nordic Seas,consequently leading to abrupt oscillations in large-scale temperature and precipitation.In East Asia,the summer precipitation in the northern part is more influenced by insolation,with a dominant precession signal.Precession-dominated insolation can influence the atmospheric circulation through its effect on the land-sea thermal contrast,which finally affects the summer monsoon precipitation.However,the summer precipitation in the southern region is more influenced by ice sheets,by their control on the meridional movement of the Inter-tropical Convergence Zone(ITCZ).In addition,the Eurasian ice sheet can further influence the precipitation in the southern part through a south-eastwards perturbation planetary wave.Moreover,the effects of insolation and ice sheets on the summer monsoon precipitation show strong regional and nonlinear characteristics,which depend on the extent,height and location of the ice sheets and the intensity of insolation.
作者
吴志鹏
尹秋珍
梁明强
郭正堂
史锋
陆浩
苏倩倩
吕安琪
Zhipeng Wu;Qiuzhen Yin;Mingqiang Liang;Zhengtang Guo;Feng Shi;Hao Lu;Qianqian Su;Anqi Lü(Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Georges Lemaître Center for Earth and Climate Research,Earth and Life Institute,Universitécatholique de Louvain,Louvain-la-Neuve 1348,Belgium;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Center for Excellence in Life and Paleoenvironment,Chinese Academy of Sciences,Beijing 100044,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2023年第12期1443-1458,共16页
Chinese Science Bulletin
基金
国家自然科学基金(41888101)资助。
关键词
水循环
降水
海冰
轨道驱动
冰盖
高低纬相互作用
water cycle
precipitation
sea ice
orbital forcing
ice sheets
high-low latitudes interactions
