ZHANG Xin-ping, YAO Tan-dong, NAKAWO Masayoshi, JIAO Ke-qin
The correlations of the (δ18O)max in the shallow ice core from the Guliya Ice Cap on the Tibetan Plateau with the global sea surface temperatures (SST) and height at the 500 hPa over the Northern Hemisphere were analyzed. The correlated regions on oceans that have an important influence on the(δ18O)max in the Guliya ice coreare all located in ocean currents or convergent regions of currents. They are the eastern Equatorial Pacific, the Northern Pacific Current, the Hot Pool in the eastern Indian Ocean, the Mozambique Current, the Northern Atlantic Current, the CanaryCurrent and the Atlantic Equatorial Current. The (δ18O)max in the core has negative correlations with the SST located in the lower latitudes, and positive correlations with that in the middle latitudes. The correlated areas at the 500 hPa that make an important impact on the (δ18O)max are located in the subtropical highs over the mid low latitude oceans and the long wave trough area over Balkhash Lake, where there are marked negative correlations between the heights in those areas and the (δ18O)max. The influencing mechanism is displayed by the diversity of the vapor origins transported to the Guliya Ice Cap. The strengths of the European ridge and the ridge over Baikal Lake have the notable positive correlations with the (δ18O)max. The two systems indirectly influence the vapor transportation towards the Guliya region by the adjustment of long-wave trough and ridge. The followings are revealed: (1) The (δ18O)max in the Guliya ice core decreases when the subtropical high over the western Pacific is strengthened and moves to the west or when the trough over Balkhash Lake becomes shallow. Contrarily, the (δ18O)max in the core increases when the high is weakened and retreats back eastward, or when the trough is deepened. (2) If the SST in the eastern Equatorial Pacific ascends anomalously duringtheprecedingwinter,i. e., when an El Ni event happens, the latitudinal Walker Circle is weakened. Simultaneously, the subtropical high over the western Pacific during the summer season is strengthened and stretches towards the west, which will lead to a decrease in the(δ18O)max.On the contrary,if the SST descendsanomalously, i. e., when a La Nia event happens, the (δ18O)max increases. (3) When the SST in the Hot Pool or in the Mozambique Current ascends, the southwest monsoon in the low layer of the troposphere is also strengthened, and therefore, the (δ18O)max in the core decreases. On the contrary, when the SST in the Pool or in the Mozambique Current descends, the (δ18O)max increases. (4) When the SST in the Canary Current descends or that in the Atlantic Equatorial Current ascends, the subtropical high over the western Atlantic and the eastern Atlantic to North Africa is strengthened, and therefore, the (δ18O)max in the core decreases. On the contrary, when the SST in the Canary Current ascends or that in the Atlantic Equatorial Current descends, the (δ18O)max in the core increases.
