摘要
南沙海区属于西太平洋暖池区，其盛冰期的表层水温变化涉及暖池在冰期旋回中的稳定性，因而具有全球性意义、本文根据十几个沉积柱状样的氧同位素与微体古生物分析结果，指出南沙海区盛冰期时夏季温度与全新世差别微小，而冬季水温强烈降低，使季节性温差高达６℃，明显超过同纬度的西太平洋开放水域。推测冰期时的冬季风强化，是造成这些变化的主要原因，同时也为热带海区冰期海面温度高、岛屿山地温度低的矛盾提出了一种新的可能解释。
The sea area of the Nansha Islands, southern South China Sea (SCS), is located within the Western Pacific Warm Pool. Its sea surface temperature (SST) variations at the last glacial maximum (LGM) are of global sighficanee because of the stability of the warm pool in the glacial cycles. Judging from outcomes of oxygen-isotope and micropaleontological analyses from over ten cores, the present paper shows that the winter SST at the LGM in the Nansha Islands sea area was about 22℃ and the summer SST was about 28℃, resulting in a seasonality as high as 6℃. Thus, the glacial / postglacial difference in summer SST (0.9 ～1.8℃) there is within the range of standard errors for the paleo-SST estimations using Transfer Function, whereas the difference in winter SST (3.3～7.3℃) is much higher than in the open Western Pacific at the same latitudes.The strengthened seasonality in the Nansha area at the LGM can be ascribed to intensified winter monsoon circulation. This also provides a new explanation for the apparent contradiction betwen the warm SST and cool montain temperature of the islands in the tropics at the LGM. There had long been a discrepancy betwen marine and terrestrial indicators of tropical climate: the SST estimations for the LGM derived by CLIMAP and recent work[3] have indicated a cooling of less than 2℃ in the tropical Western Pacific, whilst terrestrial evidences have shown that in New Guinea snow line at the LGM was by 1000～1500m lower than it is now and the vegetation zones in Sumatra and Java shifted by some five hundreds meter downslope,suggesting a 6 to 8℃ decrease in the tropical highlands. As shown by the present study, there was a significant difference in response to glacial cycles between marginal seas and open ocean. The intensified winter monsoon at the LGM might bring more snow fall in the islands to the south of the SCS and, together with the decreased SST, lower the snow line and vegetation zones in the highlands there.In sum, the remarkable decrease of SST in the Nansha area and its reduction in sea area due to the emergence of extensive shelf must have profoundly influenced the thermodynamic balance in the Western Pacific Warm Pool at the LGM, and further studies are needed to reveal the climate consequences.
出处
《第四纪研究》
CAS
CSCD
1996年第3期193-201,共9页
Quaternary Sciences
基金
南沙专项课题
国家自然科学基金
关键词
南沙海区
成冰期
气候问题
季风
古气候
Nansha Islands area, sea surface temperature, last glacial maximum, winter monsoon
