A 550,000-year record of East Asian monsoon rainfall from ¹⁰ Be in loess

Abstract

Cosmogenic Be flux from the atmosphere is a proxy for rainfall. Using this proxy, we derived a 550,000-year-long record of East Asian summer monsoon (EASM) rainfall from Chinese loess. This record is forced at orbital precession frequencies, with higher rainfall observed during Northern Hemisphere summer insolation maxima, although this response is damped during cold interstadials. TheBe monsoon rainfall proxy is also highly correlated with global ice-volume variations, which differs from Chinese cave δO, which is only weakly correlated. We argue that both EASM intensity and Chinese cave δO are not governed by high-northern-latitude insolation, as suggested by others, but rather by low-latitude interhemispheric insolation gradients, which may also strongly influence global ice volume via monsoon dynamics.

Monsoonal Forcing of European Ice‐Sheet Dynamics During the Late Quaternary

“…At the same time, the low insolation also limits the summertime melting along the southern margins of the ice sheet. Our findings of a monsoonally driven mechanism that influences the moisture supply into continental Europe and thus modulates its ice volume strongly support the hypothesis that the low latitudes were instrumental in shaping high‐latitude glaciations throughout the Pleistocene (Beck et al, ).…”

An El Niño Mode in the Glacial Indian Ocean?

“…Today, cross‐equatorial Indian monsoon winds control the modern seasonality of equatorial Indian Ocean SSTs. Available paleoclimatic evidence indicates that the boreal summer monsoons were unchanged or weakened during the LGM (Beck et al, ; Mohtadi et al, ; Sijinkumar et al, ) and thus played a minor role driving changes in seasonality. Furthermore, evidence of past changes in the intertropical convergence zone from simulations and paleodata suggests that it was weakened with limited seasonality and displaced south by up to ∼1° latitude (McGee et al, ) from its already southerly, modern position in the Indian Ocean (Schneider et al, ).…”

Late Quaternary East Asian Summer Monsoon Variability Deduced From Lacustrine Mineral Magnetic Records of Dahu Swamp, Southern China

“…However, the spatial‐temporal history of the EASM, especially monsoonal precipitation, is still not fully understood among different geological records (An et al, ; Zhang et al, ; Zhou et al, ) and model experiments (Jin et al, ; Shi et al, ) at different timescales, which may be partly because of the uncertainties in proxy interpretation and dating, but also by real spatial differences in the Asian monsoon system. In addition, the relative influence and importance of high and low latitudes as drivers of glacial/interglacial monsoon climate changes is still critical to understanding past climate processes (Beck et al, ). The traditional view in paleoclimatology was that climate changes were primarily forced by high‐latitude climate processes in the Northern Hemisphere (Denton et al, ; Grant et al, ), and thus, paleomonsoons were linked to the wax and wane of Northern Hemisphere ice sheets.…”

“…The traditional view in paleoclimatology was that climate changes were primarily forced by high‐latitude climate processes in the Northern Hemisphere (Denton et al, ; Grant et al, ), and thus, paleomonsoons were linked to the wax and wane of Northern Hemisphere ice sheets. This idea was challenged by other analyses of monsoon forcing that suggested a combined low‐latitude interhemispheric insolation gradient (Beck et al, ) and the tropical ocean‐atmosphere mean state (Yu et al, ), which involves long‐term modulation of interannual‐to‐decadal climate changes of the El Niño/Southern Oscillation (ENSO), were thought to be a coupling mechanism with low‐latitude processes (Clement et al, ; Jin et al, ; Koutavas et al, ). Hence, study of past climatic changes in low latitude areas is critical for understanding the behavior of monsoon systems and abrupt climatic changes.…”

“…As such, it is difficult to represent the entire EASM system with a single index (Wang et al, ), especially in regional precipitation. Nevertheless, most of the long‐term terrestrial records are confined to loess/paleosoil sequence and lake sediments in northern China (e.g., An et al, ; Beck et al, ; Mingram et al, ; Peterse et al, ), the paleohydroclimatic variability of EASM in subtropical southern China still remains largely incomplete owing to the scarcity of long‐term and well‐dated records. Speleothem δ 18 O records in southern and central China have been regarded as yielding the most significant and reliable information about EASM changes on various timescales (Cheng et al, ; Wang et al, ).…”