北美洲降水中稳定同位素的时空分布以及与ENSO的关系

分析了北美洲降水中δ¹⁸O的时空分布特征以及与温度、降水量、ENSO的关系.结果表明:无论是在陆地还是在海洋,北美降水中平均δ¹⁸O的纬向分布是非常显著的.随着纬度的升高,降水中δ¹⁸O迅速减小.整个北美大陆均存在温度效应,并随纬度的增加而加强.不同季节温度效应分布的差异仅表现在其范围和强度的变化上.降水量效应主要出现在低纬度海洋、中低纬度太平洋的东海岸和湾流的西北海岸.在内陆区,降水量效应不存在.不同季节降水量效应分布的差异也仅表现在其范围和强度的变化上.在大陆内部和高纬度地区,对应显著的温度效应,δ¹⁸O的季节差异Δδ¹⁸O具有较大的正值;在低纬度海洋,对应显著的降水量效应,Δδ¹⁸O较小或为负值;在相同的纬度,陆地上的Δδ¹⁸O明显大于海洋.代表大陆性特征的渥太华站和代表海洋性特征的中途岛站降水中δ¹⁸O与Ni o-4的SST具有显著的正相关关系,其中,尤以5月的δ¹⁸O与Ni o-4的SST的连续相关关系最显著,表明ENSO事件的强信号对该时期陆地和海洋降水中稳定同位素的变化具有重要影响.

Temporal-Spatial Distribution of Stable Isotopes in Precipitation and Its Relationship with ENSO over the North America

The characteristics of temporal-spatial distribution of δ¹⁸O in precipitation and its relationships with temperature,precipitation amount and ENSO were analyzed in this study.The analyses show that the latitudinal distribution of the mean δ¹⁸O in precipitation is very remarkable in the North America,regardless over lands or oceans.The mean δ¹⁸O differences between continent and ocean are less besides high latitudes.With increasing latitude,the δ¹⁸O in precipitation decreases quickly.It is found that the temperature effect appears over the whole North America continent,and becomes much more marked with increasing latitude.The variations of extension and intensity characterize a distributional difference of temperature effect on different seasons.The amount effect happens mainly in low-latitude oceans,east coast of the low-middle-latitude Pacific Ocean and northwest coast of Gulf Stream.However,no amount effect in inland.Similarly,the variations of extension and intensity characterize also a distributional difference of amount effect on different seasons.In inland and high latitudes of the North America,the Δδ¹⁸O displays greater positive value corresponding to the distinct temperature effect;in low-latitude oceans,it does smaller or a negative value;and in the same latitudes,Δδ¹⁸O in land is markedly greater than that in ocean.Furthermore,there are distinct positive correlations between SST in Nino-4 and δ¹⁸O in precipitation at Ottawa and Midway Island that stand for continental and oceanic situations respectively,in which,the continuous correlations between the precipitation δ¹⁸O in May and SST in Nioo-4 are remarkable,showing that the strong signal form ENSO has important impact on the variations of stable isotopes in precipitation of the land and the ocean in this period.