An exceptionally strengthened East Asian summer monsoon event between 19.9 and 17.1 ka BP recorded in a Hulu stalagmite

Abstract

A stalagmite-based isotope record (No. H82) from Nanjing Hulu Cave, spanning from 16.5 to 10.3 ka BP, provided strong evidence for a coherence relation between the East Asian summer monsoon (EASM) and the North Atlantic climates on millennial time scales. Here we extend the high-resolution δ 18 O time series back to 22.1 ka BP with additional 7 230 Th dates and 573 stable isotope measurements on the lower part of that sample. The new record with a decadal resolution, piecing together with the previous data, provides a detailed, complete Last Glacial Maximum (LGM)/deglacial history of the EASM. Two centennial-scale weak monsoon events are detected within the analogue H1 event, and can be correlated to corresponding Greenland temperature shifts. This suggests a rapid re-organization of atmospheric and oceanic circulations during the ice-rafted debris (IRD) event in North Atlantic. A strengthened EASM event spanning from 19.9 to 17.1 ka BP, firstly reported here, reaches on average a half of the monsoon intensity of Bølling warming with its peak close to the full level. Taking all available evidence from continental and oceanic sediments into consideration, we suggest that a forcing mechanism behind the event would be a positive feedback of the tropical Pacific Super-ENSO cycles in response to precessional changes in solar irradiation.Nanjing Hulu Cave, stalagmite, East Asian summer monsoon event Millennial climatic variability (Heinrich and DO) during the Last Glaciation, firstly identified in the Greenland ice cores [1] , was then world-widely found in various geological archives (e.g. deep sea sediments [2] and stalagmite records [3] ). A well-dated Chinese cave record indicated a positive relation between the EASM and the Greenland temperature on millennial time scales [3] . Furthermore, the coupling relationship between Super-ENSO in the tropical ocean-atmosphere system and high-north -latitude temperature was supported by Pacific planktonic foraminifera records [4] . These studies may validate a common forcing mechanism underlying the Northern Hemisphere millennial climate variability. As early found by Heinrich [5] and then confirmed later by an algae record from equatorial North Atlantic [6] , frequency of millennial scale climatic variability (including the IRD events) is in accord with half a precessional periodicity. This suggested that a nonlinear orbital forcing may play a key role in the millennial climatic variability. Indeed, model results [7] and sediment records from the Arabian Sea and the South China Sea [8, 9] suggested that the precessional forcing is the primary pacer modulating the Indian and Pacific hydrological cycles and monsoons on orbital time scales. However, relation between the millennial climatic variability in the tropics and the precessional forcing has not been revealed yet. It is generally accepted that the LGM (23-19 ka BP [10] or 22-19 ka BP [11] ) was the coldest period due to the

Implications of stalagmite density for past climate change: An example from stalagmite growth during the last deglaciation from Wanxiang Cave, western Loess Plateau

“…Stalagmite density increase also corresponds to the reflectance record of Cariaco Basin, north Venezuela, which reflects the position of the Inter-tropical Convergence Zone (ITCZ) [42]. This supports the idea that variation in Asian monsoon strength is modified by southward and northward movements of the ITCZ [5,7,8]. The gradually increasing stalagmite density matches well with increasing intensity of the Asian monsoon, especially in the transition to B/A (Figure 4).…”

“…This may lead to decrease in stalagmite density because of reduced cave dripwater rate, fewer crystallites and less crystal accretion, weakened biological activity and lowered soil pCO 2 , and increased detrital materials [21,28,[37][38][39][40] deduced from decreased precipitation associated with weakened summer monsoon. However, at short time scales the stalagmite density index shows positive correlations with the Hulu δ 18 O record [4,5] in this period, i.e. the increase in stalagmite density corresponds to more positive δ 18 O values, in contrast to the general trend.…”

“…To further verify the relationship between stalagmite density in Wanxiang Cave and environmental factors, we compared the WX42A density-time series with Hulu/Dongge Cave stalagmite δ 18 O records [4,5,8] which reflected variations in Asian monsoon intensity (Figure 4). We found that at long time scales the variation in the WX42A density index is similar to the monsoon intensity record, indicating that stalagmite density in Wanxiang Cave is controlled by Asian monsoon intensity.…”

“…Stalagmite indices such as oxygen and carbon isotopes in calcite [3][4][5][6][7][8][9][10][11], laminar thickness [12], trace elements [13][14][15], organic matter *Corresponding author (email: pzzhang@lzu.edu.cn) [16] can be used to reconstruct precipitation variability, ecological evolution and global atmospheric teleconnections. In monsoonal Asia high-precision and high-resolution stalagmite records have calibrated successfully the ice core chronology from high northern latitudes, and established connections between greenhouse gasses, ice volume and oceanic circulation on orbital millennial-centennial-decadal timescales [3][4][5][6][7][8][9][10][11]. Important breakthroughs have also been made in the relationships between Asian monsoon changes and longevity of past Chinese dynasties, as well as the impacts of human activity on the Asian monsoon [8].…”

Synchronous deglacial thermocline and deep-water ventilation in the eastern equatorial Pacific

“…1) to the δ 18 O records from the GRIP Greenland ice core (Fig. 3a)373839 and the Hulu Cave speleothems404142 (Fig. 3b).…”