INTERACTION BETWEEN THE ENSO AND ASIAN MONSOON RECORDED IN DASUOPU ICE CORE FROM HIMALAYAS

摘要

Two of the most important climate interactions between the ocean and atmosphere are the Asian monsoon in the Indian Ocean and El Niň o|Southern Oscillation (ENSO) in the Pacific Ocean. Previous analyses have variously concluded either that the Asian monsoon affects the ENSO or that the converse is true. But previous research about the relation between ENSO and Asian monsoon was focused on tropic or low|latitude ocean. There was litter research on this relation in mid|latitude continent.Dasuopu glacier is located in middle Himalayas (85 43°E, 28 23°N) at an altitude over 7000m . In 1996 and 1997, a collaboration between China and American scientists had a series of ice core drilling performed down to the bed of Dasuopu glacier. The core analysis now is still in progress. Here a record of oxygen isotopic composition and accumulation of the ice core provides a record of relation between ENSO phenomenon and the Asian monsoon.The growth rate of the core averages over 1m per year, which provides a high resolution to date layer. There is a strong seasonal cycle in δ 18 O, thus we used the seasonal δ 18 O cycle to count annual layers in the core. According to previous studying, we assigned the high δ 18 O extremes to winter. The complete δ 18 O time series indicates a increasing trend since 1980.The δ 18 O in the core correlate strongly with observed sea surface temperature (SST) over the last decade years. Thus, the δ 18 O in the ice core at the location of south Tibetan Plateau is a relatively simple proxy for SST, which is very different from that at the location of north Plateau where δ 18 O proxy for local temperature. Furthermore, the δ 18 O in the core is also corresponds with an index of monsoon strength, which demonstrates that the ice core successfully captures the large|scale aspects of Asian monsoon behavior.Generally, negative δ 18 O anomalies in the core correspond with weak monsoons, warm SST and El Niň o, on the other hand, positive anomalies correlate with strong monsoons, cool SST and La Niň o. These imply interaction between the tropics and mid|latitudes, channeled through the monsoon system.