| 摘要: |
| 未次盛冰期(LGM)是太阳辐射异常处于极低值、北半球第四纪冰流规模处于峰值、两万年来距人类环境最近但与现代气候有着巨大反差的特殊时期.70年代以来由于新资料不断积累、气候模拟技术发展、海洋大陆冰流各圈层的相关和偶合、传统的气候指标和新的气候指标的认识和应用、以及区域性和全球性的国际合作, 在LGM古气候环境领域已经取得了巨大进展本文根据数个国际LGM合作计划研究成果, 综述90年代以来全球对LGM研究方法途径和大陆古气候植被研究成果, 并对其前景提出雏议. |
| 关键词: 末次盛冰期 全球大陆 古温度 古降水 古植被 |
| DOI：10.18307/1999.0101 |
| 分类号: |
| 基金项目:中国科学院1997年度资助 |
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| Newly-Studies on Global Continental Climate and Terrestrial Yegetation during the LGM |
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YU Ge, ZHANG En-lou
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Lake Sedimentation and Environment Lab. , Nanjing Institute of Geography and Limnology, CAS, Nanjing 210008
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| Abstract: |
| Climate in the last glacial maximum (LGM) is characterized by of the lowest anomaly of orbital forcing-induced insolation, but the greatest volume of Quaternary ice sheets in the northern hemisphere during the last 20000 years.Advaces in data collection, palaeoclimate modelling, land-sea-ice correlation, interpretation of classical proxies and development of new proxies, and international cooperations for the LGM since the last published synthesis of terrestrial palaeodata of the beginning of the 70s have prompted a new evaluation of palaeoclimate and paleovege tat ions.The paper attempts to review recent international publications, syntheses the results of a few of undergoing international cooperation projects, and provides preliminary highlights for the outlooks.LGM boundary conditions can now be specified with greater confidence and precision than was possible when the first simulations of LGM land climates were performed in the end of the 1980s.Palaeoclimate modelling has advanced considerably, due to the availability of faster computers and the progressive refinement of atmospheric models.Simulations including coupling to dynamical ocean models and biosphere models can be now undertaken.Modelling intercomparsiort and therefore data-modelling comparsion can be undergoing in a global scale within the PMIP project.Acquisition of terrestrial palaeodata has continued, and in particular there have been major efforts to obtain proxy records form sediment cores in previously data-sparse regions.Dating accuracy has also been improved thanks to the increasing use of AMS for 14C-dating small samples of material of identifiably terrestrial origin.Data syntheses have been carried out on a rigorous basis starling with the Global Lake Level Data Base and the regional pollen and lake-level dala compilations carried out within the COHMAP project and continuing through the I GBP-sponsored BIOME 6000 prject, which includes the compilation of pollen records for the LGM and their translation into palaeobiomes using a standard methodology.Understanding and interpreting of the classical proxy data sources have been improved greatly.Multiproxy calibration methods have developed, ancl new proxy data sources have been developed, including the noble gas thermometer in groundwater and δ18O in speleothems as records of mean annual temperatures on land.Understanding of the temporal context of the LGM has changed drastically, due to the recognition of large, synchronous climate fluctuations during the glacial stages in high-resolution climate records from Greenland ice, marine foraminiferal records’ terrestrial pollen records and loess.Cold-month temperature of LGM was estimated form pollen and plant macrofossi 1 -based elevation shifts of vegetation belts and horizontal displacements of biomes, noble gases in gronudwa-ter and δ18O in speleothems.Cold-month anomalies ranged from -2 K at low elevations in Indonesia and the southern Pacific through -6 to -8K at many high-elevation sites to -8 to -15K in eastern China and the southeastern USA.Qualitative estimates of plant-available moisture from palaeo-ecological data and regional water balance from lake-level data, indicate LGM conditions wetter than present in westrn USA and the circum-Mediterranean region, likely associated with southward displacement of the jet stream, and at high elevations of Tibetan plateau and high mountains of Pacific islands where the effect of cooling on evaporative demands may have been decisive.The rest large lands of the world, both moisture indices show drier then present conditions elsewhere.These results are consistent with a colder than present ocean surface producing a weaker hydrological cycle and more arid continents.Developments of LGM studies in recent years have created further opportunities for exploiting a series of research projects such as International Global Atmospheric Chemistry, Global Analysis, Interpretation and Modelling, Global Changes and Terrestrial Ecosystem in global change science. |
| Key words: LGM global continents palaeotemperature palaeopreciptation palaeovegetation |
