我国低纬季风区晚冰期以来水文变化:南岭东部高分辨率湖沼沉积记录

Hydrological Variation of Monsoon-Dominated Low Latitude Region since Late Glacial:High-Resolution Lake Sedimentary Record from East Nanling Mountains,China

南岭东部定南大湖盆地湖沼相沉积高分辨率记录揭示了16.0cal ka BP以来的水文变化过程。由于该盆地主要以降水补给为主,故其水文变化过程是该地区气候与环境变化的忠实反映。多气候代用指标揭示晚冰期以来的Oldest Dryas、Blling、Older Dryas、Allerd和Younger Dryas等短尺度气候快速变化事件。10.0～6.0cal ka BP期间,该地区降水最为丰沛,暗示了夏季风在该时期最强盛,但在约9.7～9.4cal ka BP和8.8～8.2calka BP前后出现过降水骤减事件;在6.0～3.0cal ka BP期间,研究区降水显著减少,夏季风势力明显减弱。大湖盆地全新世气候变化记录与我国低纬度区域近年来的研究记录具有很好的一致性,说明低纬地区全新世适宜期应在10.0～6.0cal ka BP期间。在全球气候变化对比上,大湖盆地降水减少时期大多对应于北大西洋深水流或温盐循环减弱时期,也对应于北大西洋浮冰砾高峰时期;早全新世(10.0～6.0cal ka BP)降水丰沛期对应于北大西洋深水流加强时期;表明北大西洋深水流变化所导致的高低纬地区热量差异与我国低纬季风区过去气候变化有某种遥相关。此外,大湖盆地晚冰期以来气候变化趋势与北半球夏季太阳辐射量变化趋势吻合。因此笔者认为东亚低纬季风区晚冰期以来气候变化机制与太阳辐射量变化、大洋温盐循环等有关。

High-resolution record of lake sediments in the Dahu basin,eastern Nanling region reveals the process of hydrological variation since 16.0cal ka BP.The fact that the basin relies on supply of meteoric water implies that the process of hydrological variation indeed reflects the change of weather and environment in this region.A compound weather model can be used to unravel quick changing events of weather in a small scale since late glacial.At 10.0～6.0cal ka BP,abundant precipitation implied a strongest period of summer monsoon;at the time around 9.7～9.4cal ka BP and 8.8～8.2cal ka BP,this area witnessed a quick decreasing in precipitation;at 6.0～3.0cal ka BP,the study area encountered a distinct reduction of precipitation,and this indicates evident weakening of summer monsoon.Climate records of the Dahu basin during Holocene are consistent with those recorded recent years at China＇s low latitude areas,which indicates that optimum period at the low latitude areas is around 10.0～6.0cal ka BP.Compared with global climate change,the period of decreasing precipitation in the Dahu basin is corresponding both to that of weakening thermaline circulation（THC）and to peak period of North Atlantic floating ice;the period of abundant precipitation in early Holocene（10.0～6.0cal ka BP）is corresponding to strengthening period of thermaline circulation in North Atlantic and this shows that heat difference of high-attitude area resulted from change of North Atlantic deepwater flow may relate to the climate change in low-attitude monsoon area in the past.In addition,climate changing trend of the Dahu basin since late glacial is consistent with the change of Sun＇s radiation amount in North Hemisphere during summer.Therefore,it is believed that climate change of East Asian low-attitude regions is related to change mechanism of climate,change of Sun＇s radiation amount,and thermaline circulation.