| 末次盛冰期中国海古地理轮廓及其气候效应 |
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| 引用本文： | 谢传礼,翦知湣,赵泉鸿,汪品先.末次盛冰期中国海古地理轮廓及其气候效应[J].第四纪研究,1996,16(1):1-10. |
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| 作者姓名： | 谢传礼 翦知湣 赵泉鸿 汪品先 |
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| 作者单位： | 同济大学海洋地质开放实验室 |
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| 摘 要： | 本文是联合国政府间海洋委员会西太平洋分委员会(ＩＯＣ／ＷＥＳＴＰＡＣ)发起的“西太平洋古地理图编图计划”中国海部分的初步成果，用１０１个站位的１４Ｃ测年和２２个站位的氧同位素资料编制了本次盛冰期(２００００—１５０００ａＢ．Ｐ．)资料图、古地理图和古海洋图等三张图件。末次盛冰期低海面时中国海轮廓发生重大改观：陆架出露约１．５５×１０６ｋｍ２；表层海流改组以及表层海水温度剧降(比现代低３．５—６℃)，比当时同纬度开放大洋表层海水温度下降剧烈。海区面积减少和表层海水温度下降使中国海蒸发量大大降低。根据海陆蒸发速率差异和表层海水温度与蒸发作用之间的关系，估算出末次盛冰期中国海年蒸发量比现代降低约１２×１０(１１)—２０×１０(１１)ｍ3，或相当现代中国年降雨量的１／５—１／３。同时，末次盛冰期陆架暴露、地表反照率增高使地表对太阳辐射吸收作用减弱。总之，冰期旋回中国海在气候变化中起着重要作用。然而，要获得中国气候演化中海洋因素的定量或半定量数据尚需大量实际资料和数值模拟方能实现。
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| 关 键 词： | 末次盛冰期 古地理 中国海 反照率 |
THE PALEOGEOGRAPHIC CONFIGURATION OF CHINA SEAS AND ITS CLIMATIC INFLUENCE DURING THE LAST GLACIAL MAXIMUM |
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| Institution: | 1. Laboratory of Marine Geology,Tongji University;
2. Petroleum University |
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| Abstract: | Over one hundred sites with 14C- datings or oxygen isotope data have been collected to compile paleogeographic maps of the China Seas during the last glacial maximum (LGM) of 20000-15000 aB.P.A series of 3 draft maps (data map,paleogeographic map and paleoceanographic map) have been made, as a part of preliminary results from the IOC/WESTPAC paleogeographic mapping project.In this paper only the paleogeographic map is presented (Fig.1), and it is compiled on the basis of a total of 123 sites, of which 101 are radiocarbon-dated and 22 are constrained by stable oxygen isotope data. Twenty-seven radiocarbon-dated sites and 15 stable oxygen isotope data sites are listed in Table 1 and Table 2 respectively.The paleogeographic map at the last glacial maximum has revealed two major changes of the China Seas caused by the low sea-level stand:(1) The exposure of vast continental shelves in a total area of about 1.55 million km２. During the LGM sea level was 130-160 m lower than the present level in the East China Sea (ECS), and 100-120m lower in the South China Sea (SCS). The ECS was reduced into an elongated trough, the Okinawa Trough, with an area less than a third of its present combined size if the Bohai Gulf and the Yellow Sea are considered as its landward extention. The SCS became a semi-enclosed sac-shaped gulf connected with the Pacific mainly through thd Bashi Strait, and its area was about one fifth smaller than it is now.(2) The reorganization of surface circulations and remarkable decrease of sea surface temperature (SST). In the South China Sea the surface circulation pattern was clockwise in summer and counter-clockwise in winter, being radically different from the modern trans-basinal pattern. Due to the southern shift of the polar front in the North Pacific and the reorgnization of the surface current system, the SST in the China Seas is estimated 3.5-6℃ lower than at present, which is also remarkably lower than that in the adjacent open ocean at similar latitudes.Both the reduction of sea area and the decline of SST must have caused a decrease in evaporation from the sea surface. On the basis of the difference between evaporation rates from sea and land, and the relationship between evaporation and SST, it is estimated that the total annual evaporation from the China Seas at the LGM might be by 12×10(11)-20 ×10(11)m3/a less than at present, or 1/5-1/3 of annual total precipitation in the whole of China now.On the other hand, the exposure of shelves at the LGM must have increased the albedo from the surface and hence decreased the absorbed solar radiation.All these demonstrate the critical role played by the China Seas in the climate changes of China.Within the glacial cycles, much more practical data and numerical modelling are required, before any quantitative estimation of marine factors in the climate evolution of China becomes possible. |
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