The study looked at how the South China Sea summer monsoon onset is influenced by the Pacific and Indian Oceans. They found that from 1951 to 1970, winds over the northern Indian Ocean played a key role in the monsoon onset, while from 1970 to 1998, conditions in the western Pacific Ocean became more important. The change was due to shifts in the Arctic Oscillation and the Western Pacific Subtropical High. During the earlier period, westerly winds over the Indian Ocean and a specific ocean temperature pattern led to an early monsoon onset, while in the later period, easterly winds and warm pool temperatures in the Pacific delayed the monsoon.