A synthesis of abrupt changes in the Asian summer monsoon since the last deglaciation

Abstract

We have compiled 36 previously published palaeoclimate records to determine the timing and spatial pattern of century-scale abrupt changes in Asian monsoon precipitation since the last deglaciation. We identify abrupt events from (1) the interpretations of the authors of these records and (2) the more objective moving t-test calculation. Our results indicate that abrupt climatic changes occurred at ~11.5 cal. ka, 4.5–5.0 cal. ka and ad 1300. At the start of the Holocene (~11.5 cal. ka), Asian monsoon precipitation increased dramatically. This climatic change is synchronous with an abrupt warming in the North Atlantic. During the middle Holocene, there was a time of preferred and widespread weakening in monsoon strength (~4.5–5.0 cal. ka). This result contradicts previous notions of either a gradual trend towards drier conditions or a series of abrupt events that occurred in an unorganized fashion across space and time. The middle-Holocene abrupt event could have been synchronous with an abrupt cooling event in the North Atlantic, as well as a warming and intensification of internannual variability in the tropical Pacific. In contrast to previous periods, precipitation changes at ad 1300 have a heterogeneous spatial pattern. We find no conclusive evidence for a change in the Asian monsoon at ~8.2 cal. ka, as suggested by several previous studies. More high-resolution data may be needed to observe this short-lived event. Overall, our results attest to the potential for rapid and major shifts in Asian monsoon precipitation that may be triggered by variations in other components of the climatic system.

Variability of summer humidity during the past 800 years on the eastern Tibetan Plateau inferred from δ<sup>18</sup>O of tree-ring cellulose

“…Thus, our study site is likely influenced by the monsoon circulation (Indian and Southeast Asian monsoon) as well as by the westerlies (Morrill et al, 2003). In particular, the long-term spatiotemporal modulation of the monsoon circulation systems has been intensively studied (e.g.…”

“…In particular, the ENSO impact on the monsoon circulation has been studied extensively (e.g. Cherchi and Navarra, 2013;Kumar et al, 2006;Park and Chiang, 2010). We tested the influence of ENSO on our humidity reconstruction and achieved no significant relationships, implying an ENSO decoupled climate variability at our proxy site (see interactive discussion of this paper Wernicke et al, 2014).…”

Asynchronous evolution of the Indian and East Asian Summer Monsoon indicated by Holocene moisture patterns in monsoonal central Asia

“…Although most authors agree that the monsoonal maximum lags behind the insolation maximum, they have inferred different lag times (3000 yrs, Overpeck et al, 1996;1500yrs, Fleitmann et al, 2007; and two contrasting ideas exist concerning a gradual (Overpeck et al, 1996; Y.J. Fleitmann et al, 2007) versus an abrupt (Morrill et al, 2003) monsoon retreat pattern.…”

Assessing influences on speleothem dead carbon variability over the Holocene: Implications for speleothem-based radiocarbon calibration

“…To study the variation of DCP in speleothem records over a wide range of climatic conditions and over a range of timescales, we have created a stalagmite-based record of Holocene 14 C, as the Holocene represents the interval where atmospheric 14 C is best known based on dendrochronologically dated trees. This record, based on a Holocene stalagmite referred to as HS4 from Heshang Cave in the Hubei Province of China, is particularly well-suited for this study as it lies in the East Asian Summer Monsoon (EASM) region, a location which has likely experienced large changes in precipitation in response to changing Northern Hemisphere summer insolation (Wang et al, 2008;Morrill et al, 2003;Hu et al, 2008) and abrupt events linked to high-latitudes (Liu et al, 2013). Furthermore, as the HS4 stalagmite has been the subject of extensive paleoclimate research (Johnson et al, 2006;Hu et al, 2008;Liu et al, 2013) and Heshang Cave is the site of a long-term modern calibration study (Hu et al, 2008), robust paleoclimate records are available for comparison with the 14 C record.…”