摘要:
中国北方典型沙地处于东亚季风边缘区半干旱气候带,对气候变化响应敏感。本文对已有的该区域古气候记录文献资料进行整理分析和评估,对末次盛冰期与全新世大暖期两个特征时间段的古温度与古降雨量空间格局进行定量化重建,获得了其分布特征。 结果表明,在末次盛冰期(约26~16ka)温度降低了5~11℃,变率为60% ~200%, 降温极值在黄土高原南缘; 降雨量减少180~350mm,变率为50% 左右,东北地区降雨量变化不大。在全新世大暖期(约9~5ka),温度升高了1.0~3.5℃,变率为20% ~130% ; 降雨量增加了30~400mm,变率为10% ~120%,其中存在一些需剔除的奇异点,从东部沿海向西北内陆降雨量增幅有加大趋势。上述结果为进一步探讨中国北方干旱-半干旱区古气候变化机理、检验东亚季风区古气候数值模拟结果等提供了定量化数据。
Abstract:
Dune fields of arid and semi-arid regions of Northern China,including Mu Us field,Otindag,Horqin,Songnen,Hunlunbuir and some parts of Badain Jaran and Tengger deserts,Loess Plateau(32°~50°N,100°~135°E),are situated at margin of the area dominated by East Asian Monsoon circulation,and the environment is quite sensitive to paleoclimate change.Many paleoclimatic reconstructions have been undertaken in this region,typically from pollen,peat bog,loess-paleosol sequences,lake sediments etc,and most of these records are in good chronology sequence.In this paper,we collect and analyze the paleoclimate proxy data from more than 300 studies,datasets and relevant atlas.We find that,compared with the modern annual temperature and precipitation,the temperature decreased by 5~11℃ and the precipitation decreased by 180~350mm during the Last Glacial Maximum(LGM,26~16ka); the temperature increased by 1.0~3.5℃,and the precipitation increased by 30~400mm in Mid-Holocene Optimum(HO,9~5ka).With the comparison to the numerical simulation results,we have further discussed the mechanisms of the paleoclimate change in the LGM and HO.Our investigation shows that the paleoclimate records are not in complete consistency with the numerical simulation results; at the same time,more integrated and precise dated loess-paleosol sections have to be found,especially for the LGM in this monsoon marginal region; in addition,we need to pay more attention to the high precision paleoclimate numerical simulations with regional climate models in order to fully understand the past climate changes in dune fields in Northern China.
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