Correlation between Indian Ocean summer monsoon and North Atlantic climate during the Holocene

There has been a number of investigations for the correlation between the Asia monsoon and the North Atlantic climate for the last glacial; however, little research has been done for the present interglacial, the Holocene. Here we present for the first time a high-resolution composite proxy record for the Indian Ocean summer monsoon spanning around 12 000 years based on the δ13C time series of both a single plant species (Carex mulieensis) remains cellulose and the total plant assemblage cellulose in the Hongyuan peat bog from the Tibet Plateau. The records show that the strength of the Indian Ocean summer monsoon had abrupt variations during the last 12 000 years. The weakest monsoon occurred in the Younger Dryas period. Following rapid strengthening from around 11 200 to 10 800 a BP the monsoon kept a generally strong level for around 5300 years. From around 5500 a BP onwards the monsoon strength tended to gradual decrease. In addition, there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales, which superimpose the general tendency of the monsoon variation. In every case when the ice-rafted debris events in the North Atlantic occurred, the summer monsoon strength decreased correspondingly. These evidences show that teleconnection between the Indian Ocean summer monsoon and the North Atlantic climate is present not only in the last glacial but also in the Holocene, which may be linked to abrupt reorganizations of the ocean thermohaline circulation, leading to redistribution of energy, changing temperature and moisture gradient over the southern subtropical Indian Ocean, and eventually controlling the variability of the Indian Ocean summer monsoon.