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Abstract: The intensity variation of the East Asian Summer Monsoon during the Younger Dryas (YD) cold period remains an important scientific issue requiring clarification. In our article published in Palaeogeography, Palaeoclimatology, Palaeoecology 297 (2010) 214–222, based on the Hani peat cellulose δ 13 C sequence from Northeast China, we have documented the abrupt strengthening of the East Asian Summer Monsoon during that period. Our findings support the occurrence of wet conditions in the north and of dry conditions in the south of the Chinese Mainland, and they indicate behavior in anti-phase with the Indian Ocean Summer Monsoon that weakened during the same period. This result agrees with the previously revealed anti-phase variations of the two monsoons during the ice-rafted debris (IRD) cold events occurring in the North Atlantic Ocean. We have also proposed a theory for the anti-phase variations of the monsoons and for the anomalous distribution of precipitation. We have attributed these events to the occurrence of an El Niño-like phenomenon in the Equatorial Pacific Ocean during the YD. G. Schettler has argued that “this palaeo-climatic interpretation cannot be substantiated by chemical data from the nearby Lake Sihailongwan or by biomarker studies of the Hani peat. The inferred inverse correlation between the summer monsoon strength in northeast and southern China during the Younger Dryas appears questionable.” However, after carefully examining Schettler''s [G. Schettler, Comment on “Anti-phase oscillation of Asian monsoons during the Younger Dryas period: Evidence from peat cellulose δ13C of Hani, Northeast China” by B. Hong, Y.T. Hong, Q.H. Lin, Y. Shibata, M. Uchida, Y.X. Zhu, X.T. Leng, Y. Wang and C.C. Cai [Palaeogeography, Palaeoclimatology, Palaeoecology 297 (2010) 214–222], Palaeogeography, Palaeoclimatology, Palaeoecology, this issue] water chemistry data from Lake Sihailongwan, we find considerable accumulation ratios of biosilica during the YD period that clearly indicates abrupt strengthening of the East Asian Summer Monsoon. We point out that Schettler referred incorrectly to Zhou''s research results. Zhou et al. have clearly indicated that elevated n-alkane P aq values and C23/C29 ratios serve to record an especially moist local climate in YD. We also confirm that the influence of an increased relative contribution of Sphagnum species to Hani peat composition on peat cellulose δ 13 C is negligible. Therefore, our conclusions that, during the YD cold period, the EASM abruptly strengthened and that, moreover, an anti-phase occurred between the two Asian monsoons during the YD period, are both, in fact, substantiated not only by biomarker studies of the Hani peat but also by chemical data from the nearby Lake Sihailongwan. We therefore consider Schettler''s statement to be untenable. [Copyright &y& Elsevier]

Abstract: Significant changes in the global atmospheric and oceanic circulation system occurred during the Younger Dryas cold period. Several researchers have demonstrated a weakening of intensity of the Indian Ocean Summer Monsoon during that period. However, the exact characteristics of the East Asian Summer Monsoon still remain vague. Here we present a late-glacial precipitation proxy record of the East Asian Summer Monsoon, based on the peat cellulose δ13C found in Hani, Northeast China. Both the peat cellulose record and a pollen record from Lake Sihailongwan sediment indicate an abrupt increase in precipitation in the region during the Younger Dryas period. These results support the occurrence of wet conditions in the north and of dry conditions in the south of the Chinese Mainland during that period. By examining the activity of the East Asian Summer Monsoon on an interannual timescale, we propose a theory for the anomalous precipitation distribution that we attribute to the occurrence of an El Niño-like phenomenon in the Equatorial Pacific Ocean during the Younger Dryas. In this case, the intensity of the Western Pacific subtropical high may strengthen, and its position over the western Pacific Ocean may move northward. This could cause an enhancement of the East Asian Summer Monsoon and migration of a monsoonal rainbelt towards the northern region of the Chinese mainland, resulting in a precipitation distribution of wet conditions in the north and dry conditions in the south. Therefore, this anomalous rainfall distribution should be considered to indicate the strengthening of the East Asian Summer Monsoon, in anti-phase with the Indian Ocean Summer monsoon that weakened during the same period. This agrees with the previously revealed anti-phase variations of the two monsoons during the ice-rafted debris cold events of the North Atlantic Ocean. It appears that, in relation to the abrupt temperature drop in the Northern Hemisphere on centennial to millennial time scales, anti-phase variations of the two Asian summer monsoons occurred. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]